Diet, Depression, and Anxiety

The aim of this 2020 review was to explore the relationship between macronutrients, such as carbohydrates, fats, and proteins, with depression through analysing national survey datasets from the United States and South Korea. The data were taken from the National Health and Nutrition Examination Survey (NHANES)(60,935 subjects) and from the South Korea NHANES (K-NHANES)(n = 15,700) databases. In both the United States and Korea samples, a 10% increase in the proportion of calorie intake was associated with a significant decrease in the prevalence of depression. The low protein intake groups, on the other hand, had significantly higher risk of exhibiting depressive symptoms than the normal protein intake groups in both countries. In terms of carbohydrate intake, an association with incidence of depression was found in the United States but not in South Korea. Fat intake was not significantly associated with depression in either country. The results demonstrated that the pattern of associations between macronutrients and depression in Asian American and South Korean populations were similar. The findings suggest that the proportion of macronutrient intake in everyday life may be related to the occurrence of depression.

This 2019 study, the first RCT to assess young adults, tested the positive association between “healthy” diet consumption and reduced depressive symptoms. It targeted young adults with elevated levels of depression symptoms who did not eat healthily. The 101 young adults were randomly categorised into either the diet group (which implemented a diet alteration for 3 weeks) or the control group (which consumed their habitual diet) and were examined on symptoms of depression (Centre for Epidemiological Studies Depression Scale (CESD-R); Depression Anxiety and Stress Scale– 21 depression subscale (DASS-21-D)), memory (Hopkins Verbal Learning Test), current mood (Profile of Mood States) and self-efficacy (New General Self-Efficacy Scale) at baseline and after the intervention. Diet compliance was also determined through self-reported questionnaires and spectrophotometry. The results showed that the Diet group reported significantly fewer symptoms of depression than the control group on the CESD-R (p=0.007) and DASS-21 depression subscale (p=0.002) while controlling for baselines scores on these scales. The lower DASS-21 depression scores were maintained 3 months later, as determined by follow-up phone calls. These are promising signs for diet interventions to be utilised in the management of depression.

This 2020 systematic review analysed 20 different studies to review the scientific evidence on the effectiveness of dietary habits as treatment strategies for depression. By conducting narrative synthesis, the following dietary components were found to aid in alleviating depression: fatty acid intake; fish consumption; the micronutrients folic acid and magnesium; diets of anti-inflammatory nature; and lack of processed food. High adherence to dietary recommendations is vital, as are healthcare professionals offering support and encouraging healthy diets. Further research by public health would be required to define precise strategies for prevention and management.

First to do so, Firth et. al (2019) conducted a systematic review and meta-analysis looking at the overall evidence of dietary interventions for improving symptoms of depression and anxiety. The 16 randomised controlled trials included a total of 45,826 participants, and reported shifts in depression and/or anxiety symptoms in clinical and non-clinical populations (all but one included was clinical). Random-effects meta-analyses were used to determine the effect sizes that diet interventions had in comparison to the control groups. Dietary interventions were shown to reduce depressive symptoms (p=0.002), even when focusing exclusively on high-quality trials (p=0.002). The results were also similar when compared with inactive (p=0.038) and active controls (p=0.035). Another finding was that female populations experienced greater beneficial effects in reducing their depression and anxiety, although no effect of dietary intervention was proven for anxiety. This meta-analysis/systematic review demonstrates that dietary improvements possess the potential to lower depressive symptoms across the population.

Salari-Moghaddam et al. (2019) explored the association between MIND diet adherence and risk of developing psychological disorders (first study on this topic). A total of 3,176 adults participated in this cross-sectional study. MIND diet scores were calculated using the participants’ dietary intake (taken from the validated dish-based 106-item semi-quantitative food frequency questionnaire (DS-FFQ) completed by the individuals). Depression and anxiety were determined through the use of the Iranian validated version of Hospital Anxiety and Depression Scale (HADS), and psychological stress was measured by the General Health Questionnaires (GHQ). After accounting for possible confounding variables, the data showed that those in the highest quartile of the MIND diet score had a lower incidence of depression (OR 0.68) and of psychological distress (OR 0.72) when compared to the lowest quartile. Anxiety was not significantly associated with the MIND diet. In gender-stratified analyses, females in the top MIND score quartile had lower odds of depression (OR 0.6) and psychological distress (OR 0.66) than those in the lowest quartile, which was not observed in the males. Adherence to the MIND diet was found to reduce the risk of developing depression and psychological distress, although it could not be strongly linked with reductions in anxiety.

Jacka et al. (2017) executed this 12-week, single blind, randomised controlled trial to investigate the efficacy of a dietary improvement program for the treatment of major depressive episodes. The intervention consisted of seven individual nutritional consulting sessions delivered by a clinical dietician. The control condition was comprised of a social support protocol adhering to the same visit schedule and length. Of the 67 individuals who enrolled in this trial (33 = diet intervention, 34 = control), 55 participants were using some form of therapy: 21 using psychotherapy and pharmacotherapy combined; 9 were on psychotherapy alone; and 25 were exclusively using pharmacotherapy. With 31 participants in the diet support group and 25 in the social support group with complete datasets at 12 weeks, the dietary support group was found to have significantly improved MADRS (assesses depression symptomatology) between baseline and 12 weeks, compared to the social support group (p<0.001). Remission, defined as a MADRS score <10, was achieved for 32.3% (n = 10) and 8.0% (n = 2) of the intervention and control groups, respectively; the number needed to treat (NNT) based on remission scores was 4.1 (95% CI of NNT 2.3-27.8); and a sensitivity analysis discovered that the impact of the intervention was robust to violations of MAR assumptions. Jacka et al. (2017) believe that these results demonstrate that improvements made to diet may be an efficacious and accessible treatment option for major depression and also benefit common comorbidities.

In this publication, Jacka et al. (2018) share their comments on the SMILES trial, which was the first randomised controlled study to experiment with dietary improvements for the treatment of depression. They address concerns raised by Molendijk et al., namely that the expectation bias and difficulty blinding may have contributed to the end-result in the SMILES trial. Expectation bias can occur in lifestyle intervention studies, which was acknowledged in this article. However, a strong correlation between diet alterations and varying depression scores were observed in the original study, and it was argued that many studies published later have produced the same results, deeming inadequate blinding in the SMILES trial to be unlikely. Jacka et al. propose that the SMILES trial should be regarded as an important preliminary step in the field of nutritional psychology research.

Chatterton et al. (2018) collected data from and evaluated the cost-effectiveness of the SMILES trial, which demonstrated the efficacy of dietary interventions (a significant improvement in Montgomery-Asberg Depression Rating Scale scores was seen in the diet support group compared to a control group over 12 weeks). The trial involved participants being randomized into either seven sessions with a dietician for dietary support, or an intensity-matched social support (befriending) control condition. Evaluating the costs from health sector and societal perspectives, data on food and travel costs, medications, medical services, workplace absenteeism and presenteeism were collected using a resource-use questionnaire. Standard Australian unit costs for 2013/2014 were applied before incremental cost-effectiveness ratios (ICERs) were calculated by dividing the average cost difference between groups by the difference in average Quality Adjusted Life Years (QALY, the primary outcome of the SMILES trial). Compared with the social support condition, average total health sector costs were $856 lower and average societal costs were $2591 lower for those receiving dietary support. These differences were driven by lower costs arising from fewer allied and other health professional visits and lower costs of unpaid productivity. Although significant differences in mean QALYs were not found between groups, 68% and 69% of bootstrap iterations showed the dietary support intervention was dominant, meaning additional QALYs at a cheaper price, from the healthcare sector and societal perspectives. Therefore Chatterton and researchers (2018) found the dietary support intervention likely to be cost-effective as an adjunctive treatment for depression.

Seeking new psychiatric strategies for prevention and treatment, Altun et al. (2019) conducted a systematic review of the current evidence on the association between the Mediterranean diet and depressive symptoms. Twenty observational studies and six intervention trials found in the computer databases Medline, Embase, PsychINFO, Scopus and Google Scholar were included. 85% of the observational studies and all six intervention trials supported the claim that the Mediterranean dietary pattern is inversely associated with incidence of depression. The lack of methodological disparity in the Mediterranean style diets studied restricted comparisons, but this was combatted by using specific criteria and performing compressive data appraisal. This review encourages global implementation of dietary changes in the treatment of depression, which could cut down costs and produce fewer side effects. It also acknowledges the need to define specifically what a Mediterranean diet entails, and the need for further research on this topic (clinical trials included).

Suboptimal intake of fruit and vegetables (FV) is becoming more prominently recognised as a risk factor for cardiovascular disease and cancer. Lock et al. (2005) estimated the global burden attributed to suboptimal intake of FV, and compared its impact with that of other major risk factors for disease. They found that total worldwide mortality attributable to low FV consumption could be up to 2.635 million deaths per year, and that increasing FV intake to 600g daily could reduce the disease burden by 1.8%, including lessening the burden of ischemic heart disease by 31% and ischaemic stroke by 19%. Its potential to reduce incidences of stomach, esophageal, lung and colorectal cancers was slightly lower at 19%, 20%, 12% and 2% respectively. This study highlights the importance of increasing daily fruit and vegetable intake in relation to lowering the risk of many non-communicable diseases. It also calls for greater inclusion of these important risk factors in public health policies.

The research topic of this 2019 Korean study was whether a higher diet quality score in 19-64 year olds would relate to a lower chance of showing depressive or anxiety symptoms, and higher quality of life (QoL.) The diet quality of 1,295 participants of the National Fitness Award Project was examined through the use of the recommended food score (RFS), while psychological health and quality of life (QoL) were assessed by the beck depression inventory (BDI), beck anxiety inventory (BAI), and the World Health Organisation QoL-Brief (WHOQoL-BREF). After adjusting the data for covariates, the results showed that participants without depression had a significantly higher RFS value than the participants with depression in both male and female populations. The highest tertile group of RFS were observed to have a lower incidence of depression (OR =0.51, CI = 0.32-0.81, p-trend = 0.0043) and a drop in the risk of scoring a QoL below the median (OR=0.4, p<0.001), in comparison to the lowest tertile group. The data could not support an association of anxiety with RFS. However, it did suggest that a better quality diet relates to fewer depressive symptoms and higher quality of life in Korean adults.

This is a systematic review of observational studies analysing the relationship between fruit and vegetable (FV) intake and mental health in adults. There were 61 studies included in the review, drawn from either Pubmed or Web of Science databases dated up to June 2019, or found through manual search in relation to the previously discovered studies. The included studies mainly centred around depression and depressive symptoms, but there were also some on general and mental well-being, quality of life, sleep quality, life satisfaction, flourishing, mood, self-efficacy, curiosity, creativity, optimism, self-esteem, stress, nervousness, happiness, anxiety, minor psychiatric disorders, distress, and attempted suicide. By adopting narrative synthesis analysis, the researchers noted that a higher intake of FV (and some of their subgroups like berries, citrus, green leafy vegetables) may lead to higher levels of optimism, self-efficacy, and reduced likelihood of experiencing psychological distress, depressive symptoms, ambiguity, and even cancer fatalism. Acknowledging limitations due to disparities in methodology and populations across these studies, Głąbska and colleagues (2020) conclude that there is a vast majority of studies that suggest fruits and vegetables, and processed FV products alike, have a positive effect on mental health.

This study focuses on consumption frequencies of the main food categories in an elderly Taiwanese population, and how it relates to the risk of developing new depression in the future (assessed after 4 years). Logistic regression analysis was performed, while also controlling for possible confounding factors. There were a total of 1,609 participants aged over 65. When controlling for demographic, socio-economic, lifestyle, and health-related variables, but not cognitive status, both fruits (OR=0.66, p=0.038) and vegetables (OR=0.38, p=0.021) were protective against new depression in 4 years time. The results changed slightly when controlling for cognitive status as well: only vegetables (OR=0.4, p=0.039) reduced incidence of depression. Greater intake of eggs almost had a significant impact in both regression models (p=0.087 and 0.069), while no significant evidence could be found linking meat/poultry, fish, seafood, dairy, legumes, grains, or tea with the reduction of future depression. These results suggest that increasing frequency of vegetable consumption may protect elderly populations from developing depressive symptoms.

Due to present contradictory evidence, Saghafian et al. (2018) used this observational study to investigate the relationship between fruit and vegetable (FV) intake and the prevalence of depression, anxiety, and psychological distress in Iranian adults. A 106-item food frequency questionnaire (FFQ), Iranian-validated version of Hospital Anxiety and Depression Scale (HADS), and General Health Questionnaire (GHQ) were used to assess dietary habits, anxiety and depression, and psychological distress, respectively, in 3,362 Iranian adults. The women in the top quintile for fruit consumption were seen to have lower odds of depression, anxiety, and psychological distress (57%, 50%, 60% respectively) compared with women in the lowest quintile. Vegetable consumption was significantly associated with lower odds of depression (OR=0.65) in women and with lower incidence of anxiety (OR 0.43) in men. After adjusting for potential confounding variables, similar trends were observed: Iranian women belonging to the highest quintile of FV intake have significantly reduced odds of depression (OR=0.55) and psychological distress (OR=0.60) compared to females in lowest quintile; men also see higher levels of FV intake correlate with in a drop in psychological distress (OR=0.42). The researchers concluded that increased FV consumption in Iranian women had a greater degree of beneficial influence than in men with regard to psychological distress, anxiety, and depression, while eating more vegetables lowered the possibility of depression and anxiety in women and men, respectively. The likelihood of suffering depression and psychological distress was lowered in both sexes when higher quantities of fruit and vegetables were included in their diets.

This study examined 3,172 Iranian adults in order to correlate adherence to the Mediterranean Diet (MeD) and the prevalence of psychological disorders. Participants aged 18-55 were included in this cohort, and their psychological health, psychological distress, dietary intake, and adherence to the MeD were all assessed through the use of the Iranian validated version of the Hospital Anxiety and Depression Scale (HADS), General Health Questionnaire (GHQ), a validated food frequency questionnaire (FFQ), and Trichopoulou et al. method, respectively. Participants most adherent to the MeD showed a lower risk for depression (OR=0.60), anxiety (OR=0.61), and psychological distress (OR=0.60) compared to those with the lowest adherence. When examining the components of the MeD, the study inversely associated high fruit and vegetable consumption with risk of depression, anxiety, and psychological distress, while grains were positively associated with depression, anxiety, and psychological distress.

As dietary fibre is linked with depression via the gut microbiome, Ramin et al. (2020) investigated its association with mental health-related quality of life (QoL) scores, analysing the 14,129 postmenopausal women in the Iowa Women’s Health Study. Using a 127-item food frequency questionnaire to assess baseline dietary intake in 1986, the study followed up in 2004 with questionnaires consisting of a Mental Health (MH) component and a Mental Health Composite (MHC) scale to calculate mental health-related QoL scores. The median dietary fiber intake was found to be 19g per day, and ranged from 1.1g to 89.4g daily amongst the female population. The average mental health score, after being adjusted for various factors such as age, alcohol consumption, physical activity, smoking status, education, energy intake, and waist-to-hip ratio, were discovered to be higher in those consuming larger quantities of fibre (P=0.02). When the data was adjusted for age and energy intake, the relationship between dietary fibre and MCS scores became insignificant. This recently published study is one of the first to link high fibre intake to increased future mental health-related QoL scores. Further research is called for to supplement this data.

Akbaraly et al. (2013) examined 4,215 participants from the Whitehall II Study on dietary patterns (using the Alternative Healthy Eating Index (AHEI)) and display of depressive symptoms at follow-up. The present study aimed to test the theory that adherence to a healthy diet may lead to reduced risk of developing depressive symptoms. In cases where a participant scored 16 or more on the Centre for Epidemiological Studies Depression Scale, or self-reported antidepressant use, the participants was defined as having recurrent depressive symptoms. The results showed that women who maintained high AHEI scores or improved their diet scores benefitted from a 65% and 68% (respectively) reduction in risk of developing recurrent depressive signs later on, compared to those with consistently low AHEI scores. The inverse association between AHEI scores and recurrent depressive symptoms was only observed in the female population (OR=0.59; 95% CI 0.47-0.75, p<0.001). While examining AHEI components, it was found that vegetables, fruits, trans fats, and the ratio of polyunsaturated fat to saturated fat components correlated with recurrent depressive symptoms in women. Poor diet is suggested to be a risk factor for future depression in women, which may spark a new aim for a public health campaigns targeting women's depression.

Nicolaou et al. (2019) claim the evidence presented to date of varying dietary patterns having an impact on depression is inconsistent. Therefore, they looked at the association between dietary pattern and depressive symptoms, using data from six cohorts taken from several countries, including Italy (INCHIATI), the Netherlands (LASA, NESDA, HELIUS), Australia (ALSWH), and the UK (Whitehall II). Cross-sectional data from a total of 23,026 subjects was gathered, and the findings subjected to meta-analysis. The researchers used the cohorts with repeated measures of depressive symptoms (from 5-6 year follow-ups) for the analysis of depression incidence (Whitehall II, InCHIANTI, ALSWH). Three 'a priori' dietary patterns — Mediterranean Diet Score (MDS), Alternative Healthy Eating Index (AHEI-2010), and the Dietary Approaches to Stop Hypertension (DASH) diet — were examined in relation to depressive symptoms. While individual cohort analyses were adjusted for confounding variables, this meta-analysis used a random-effects model. The researchers identified a significant inverse association of the three dietary patterns with depressive symptoms (incidence of depression was significantly lower in those who scored higher MDS, AHEI-2010, and DASH). This provides further indication that adults who follow a healthy dietary pattern are less likely to develop depressive symptoms, and see fewer symptoms if they do experience depression.

In this 2016 study, the relationship between adherence to healthy eating guidelines (measured by the Alternative Healthy Eating Index (AHEI-2010)) and depression was investigated in an Iranian population. First, dietary information was taken from the 3,363 participants using a 106-item semi-quantitative food frequency questionnaire (FFQ). Through the Hospital Anxiety and Depression Scale (HADS), the prevalence of depression and anxiety were found to be 15.2% (males 10.8%, females 18.3%) and 30% (males 22.9%, females 35.1%), respectively. In the multivariate-adjusted model, adults with higher adherence to healthy diets (top quartile of AHEI-2010) were 49% and 45% less likely to suffer from anxiety and depression, respectively, than those in the bottom quartile. When stratified analysis was employed, a variation in results between the two sexes was observed: while no significant association could be found in males, women in the highest categories of AHEI-2010 had an odds ratio of 0.51 for depression and anxiety. In the subpopulation aged 40 and under, individuals adhering closely to AHEI-2010 were 58% and 51% less likely to suffer from anxiety and depression, respectively, than those who were less compliant. Adherence to healthy diets seems to be effective in lowering the occurrence of depression and anxiety in Iranian adults.

This review focuses on the importance of diet on anxiety and anxiety-like behaviour, and inspects the current literature on how food components can influence anxiety at various stages of development, from gestation to adult life. Studies have established psychology, physiology and behaviour are interlinked, and that nutrition and anxiety can have both independent and interactive negative effects on health. The unbalancing of one of these factors can have a great impact on an individual, which may place a large importance on individual cognitive ability, diet and external environments. This review breaks down the available studies on how diet affects anxiety, highlighting limitations of the cohorts, and gaps in our understanding (namely food interactions and contemporary diets throughout the life course and at the physiological, metabolic psychological and emotional level), which could encourage future research into what Murphy and Mercer (2013) find to be lacking.

This 2019 systematic review, which examined adherence to a healthy diet in relation to depressive symptoms or clinical depression, was designed to find an association between diet quality and depressive outcomes. Amongst the studies used were 20 longitudinal and 21 cross-sectional designed cohorts, employing an array of dietary measures including adherence to Mediterranean Diet assessments, the Healthy Eating Index (HEI) and Alternative HEI (AHEI), the Dietary Approaches to Stop Hypertension, and the Dietary Inflammatory Index. Encouraging evidence was observed especially for Mediterranean Diet and incident depression, as a combined relative risk estimate of highest against lowest adherence from 4 longitudinal studies was calculated to be 0.67 (95% CI 0.55-0.82). Furthermore, again in 4 longitudinal studies an association between lower dietary inflammatory index with a drop in risk of depression (RR 0.76). Additional longitudinal studies with other indices suggested the same trend in the inverse association between healthy diet and depression. This systematic review concluded adhering to a Mediterranean Diet and low inflammatory diet can offer protection against depression in observational studies.

This was a 2018 systematic review and meta-analysis of 27 publications associating fruit and vegetable (FV) intake and depression. 16 cross-sectional, 9 cohort and 2 case-control studies found in Medline/Pubmed, ISI, SCOPUS and Google Scholar until 2017 that focused on fruit, vegetable, and/or total FV intake in relation to depression were all included in this review. The pooled relative risk (RR) for depression in the highest vs lowest fruit consumption groups was 0.83 in cohort studies and 0.76 in cross-sectional studies. When consumption of vegetables was analysed the RR of depression was again lower in cohort studies (RR=0.86) and in cross-sectional designed studies (RR=0.80). A 20% lower incidence of depression was also seen when total FV consumption was analysed in cross-sectional studies. When meta-regression of the included observational studies was conducted, an inverse linear link between fruit or vegetable intake and incidence of depression (for every 100g of fruit consumed risk of depression decreased 3% in cohort studies; reduced chances of depression by 3% and 5% were also seen in cohort and cross-sectional studies respectively every 100g of fruit was eaten). These findings reinforce the recommendations of increasing fruit and vegetable intake to improve mental health.

This 2016 cross-sectional study investigated dietary intakes of soluble, insoluble, total and sources of fiber and their relationship with depressive symptoms in a Japanese adult population (19-69 years of age). A total of 1977 employees signed up for the experiment, which involved the uses of diet history questionnaires to assess dietary intake, and the Centre for Epidemiological Studies Depression Scale to report depressive symptoms. Fibre intake from fruits and vegetables was shown to significantly reduce depressive symptoms. The multi-variable adjusted odds ratio for the groups with lowest fruit and vegetable consumption attributes up to the highest were as follows: 1.00(reference), 0.80 (CI 0.6-1.05), and 0.65 (CI 0.45-0.95) respectively with p value for trend of 0.03. Although soluble, insoluble and total fibre in meals could not be associated with depression, this study demonstrates the preventative potential of greater fruit and vegetable intake in management of depressive symptoms.

This review explored the action of dietary fibers on inflammation and depression, and the poorly understood mechanism between the two. This included looking at microbiota-driven modification of gene expression and increased neurotransmitter production as possibilities. Swann et al. (2020) identified a possible mediatory effect of inflammation on the relationship between depression and fibre in the diet. By potentially altering the pH and permeability of the gut, a high-fibre diet may result in reduced inflammation and in turn decrease the collection of neurotransmitters, lessening the symptoms of depression. These encouraging findings could promote further research into the link between dietary fiber and depression and inflammation.

Hilimire, DeVylder, and Forestell (2015) hypothesized that fermented foods likely to contain probiotics may relate to neuroticism and social anxiety symptoms, given the established evidence for probiotics possessing an anxiolytic influence. Fermented foods intake, neuroticism and social anxiety were self-reported by 710 young adults in this experiment. An interaction model revealed that neuroticism, exercise frequency, and fermented food consumption significantly and independently predicted social anxiety. Importantly, more frequent consumption of fermented foods in those high in neuroticism resulted in fewer symptoms of social anxiety. This study suggests that fermented food products likely to contain probiotics may be a useful and cost-efficient way to prevent/manage anxiety symptoms especially in individuals with neuroticism tendencies.

Data from 1,634 adults from the Netherlands Study of Depression and Anxiety was used in this 2018 study. At the 9-year follow up, their data was extracted to explore the association between depressive and anxiety disorders and their subtypes (disorder type, severity, chronicity, clinical) with diet quality. Composite International Diagnostic Interviews were conducted to identify depression and anxiety disorders, while the disorders' severity was gauged using the Inventory of Depressive Symptomatology (IDS), Beck Anxiety Inventory, and Fear Questionnaire. Diet quality was assessed with the Mediterranean Diet Score (MDS) and Alternative Healthy Eating Index (AHEI), while chronicity was measured with life-chart interviews. Compared to the healthy control group, participants with a disorder were seen to have significantly poorer diets. When the subject population was further subdivided, it was evident that the lowest diet quality scores were observed in those with concurrent depressive and anxiety disorders. In fact, greater chronic depression or anxiety disorders and increased severity in the whole test population showed a dose-response association with lower quality dietary intakes. As poorer diet quality was linked to the presence of depressive and anxiety disorders as well as severity and chronicity of symptoms, further research into whether enhancing diet quality could positively affect mental health is warranted.

To explore which component of the Mediterranean diet can be attributed to the association between adherence to this diet and fewer depressive symptoms, Gibson-Smith et al. (2020) analysed the food groups of the Mediterranean Diet Score (MDS) independently and in combinations, and explored their relationships with severity and diagnosis of depression and anxiety. Data from 1,634 subjects from the Netherlands Study of Depression and Anxiety was extracted for this cohort, also documenting information on food groups using the food frequency questionnaire. Regression analysis was then performed using the incidence of depressive and anxiety disorders (established using Composite International Diagnostic Interview) and disease severity (measured with the Inventory of Depressive Symptomatology, Beck Anxiety Inventory, and the Fear Questionnaire). A total of 12 food groups were looked at based on those in the MDS, including alcohol consumption. The severity of depression and anxiety lessened as higher levels of non-refined grains and vegetables were consumed, while the inverse was seen within the non-drinkers. Those non-drinkers were also at greater risk of current depression/anxiety disorders as compared with the control population, while those on more non-refined grain enriched diets had favourable odds. Higher fruit and vegetable consumption was linked to lower fear severity. It is indicated in the study that non-refined grains, vegetables and alcohol intake may play influential roles in the positive association between MDS scores, and depression and anxiety, which in turn signifies supplementary studies may be required to test the protective function of non-refined grains and vegetables in depression and anxiety.

While there is significant evidence for a link between metabolic conditions (including obesity and diabetes) with neuropsychiatric disorders, the mechanisms of pathogenesis involving the relationship between these conditions can be difficult to decipher. Melo et al. (2019) reviewed the current research examining the relationship between neuropsychiatric disorders and diet-related nutritional imbalance, with a focus on the mechanisms of inflammation that are activated by dietary fatty acid intake (refined fats and sugars). The authors note that this is a particularly relevant area of study due to the significant changes in societal eating patterns towards a Western-style diet (i.e., high in processed fats and sugars). In this review, the authors discussed the mechanisms by which dietary fatty acids signal inflammatory processes that lead to neuroinflammatory conditions.

Sangsefidi et al. (2020) extracted data from 9,965 adults from the population-based cohort study — the Yazd Health Study (YaHS) conducted during 2014 to 2016 — to assess the association between dietary intakes and psychiatric disorders in Iran. Psychological and physical activity assessments were carried out using depression, anxiety, and stress scale questionnaire (DASS 21 items) while a validated researcher-made questionnaire and anthropometric measurements were used to collect information on socio-demographic characteristics, tobacco use, history of chronic disease, and diet. The results included a positive association between fish consumption and depression (OR=1.54), and inverse associations between vegetable intake with anxiety (OR=0.74) and stress (OR=0.59). Moreover eggs, fruits, milk and yoghurt were found to exhibit protective effects against depression and anxiety, while a drop in incidence of stress was linked to fruit and milk intake. Additional studies are required to support these associations, which could be used in future health promotion programs.

The authors start by exploring the connection between nutrition and depression, in which nutrition can play a key role in the onset, severity and duration of depression. The most well-known eating patterns indicative of depression — such as poor appetite, skipping meals, and a strong desire for sweet foods — also occur in the lead up to depression. Rao et al. (2008) write about nutritional neuroscience and aim to shed light on the relationships that exist between nutritional factors and human cognition, behavior and emotions.

The aim of this study was to examine the associations between regular intake of dietary flavonoids with depression risk. Chang et al. (2016) studied 82,643 adult women without a previous history of depression at baseline in this study (depression was defined as physician- or clinician-diagnosed depression or antidepressant use). A total of 10,752 cases of depression were registered during the 10 year follow-up. The study revealed that flavonoids, including flavonol, flavone, and flavanone, were inversely associated with depression risk. In flavonoid-rich food-based analyses, the HR was 0.82 among participants who consumed ≥2 servings citrus fruit or juices/d compared with <1 serving/wk. When looking at one of the studies used in particular [Nurses’ Health Study (NHS)], total flavonoids, polymers, and proanthocyanidin intakes indicated a significantly (9-12%) lower risk of depression. In examining the older NHS participants (aged ≥65 y at baseline or during follow-up), greater consumption of all flavonoids, with the exception of flavan-3-ols, was linked with significantly lower depression risk, with flavones and proanthocyanidins showing the strongest associations. Although further studies are required to support these associations, it could be deduced that higher flavonoid inclusion in the diet may be associated with lower depression risk, especially among older women.

Martínez-González and Sánchez-Villegas (2016) review the evidence on the association between several food patterns with reduced depression risk, which seem to be consistent across countries, cultures, and populations (according to several systematic reviews and meta-analyses of observational studies). Of all the food patterns thought to be effective in lowering future risk of depression (including the Alternative Healthy Eating Index, the Prudent diet or the Provegetarian Food Pattern) only the Mediterranean Food Pattern has been tested for primary prevention in a large randomised trial (inverse association was not statistically significant). According to large and well-designed observational studies, food patterns potentially associated with reduced risk of depression are those emphasising seafood, vegetables, fruits and nuts. With some guidelines concluding that the evidence is limited, the authors express the need for further exploration into how the incorporation of different micro- and macro-nutrients into one's diet can potentially influence depressive risk.

This 2018 cross-sectional study assessed 16,807 adults (aged 20 years and over) on dietary consumption (obtained through two 24-hr dietary recall interviews) and depressive symptoms (using the Patient Health Questionnaire) with the aim of exploring the association between dietary fibre intake and the risk of developing depression. Results showed that dietary intakes of total, cereal, vegetable, and fruit fibre were inversely associated with depressive symptoms in unadjusted model and multivariate-adjusted model 1. Also, in multivariate-adjusted model 2, when the highest quintile was compared to the lowest quintile with respect to total, cereal, vegetable, and fruit fibre intakes, the odds ratios of depressive symptoms were 0.59, 0.90, 0.58 and 0.64, respectively. While dose-responses analyses revealed the non-linear association between total fibre consumption and depression risk, the relationships with cereal, vegetable and fruit fibre intake were found to be linear. While further larger prospective studies are required to confirm these findings, Xu et al. (2018) and their results suggest inverse associations between consumption of total fibre, vegetable fibre, and fruit fibre with depressive symptoms.

Godos et al. (2018) studied 1,572 adults living in Southern Italy, aiming to assess the association between habitual dietary intake of total polyphenols, their classes, subclasses, and individual compounds with depressive symptoms among participants of the Mediterranean Healthy Eating, Lifestyle and Ageing (MEAL) study. Food frequency questionnaires, Phenol-Explorer, and the Center for Epidemiological Studies Depression Scale (CES-D-10) were used to calculate habitual polyphenol consumption and to screen for depressive symptoms, respectively. Based on 509 participants who reported depressive symptoms, total polyphenol intake could not be associated with depressive symptoms. Following adjustment for potential compounding factors, dietary intake of phenolic acid (OR = 0.64), flavanones (OR = 0.54), and anthocyanins (OR = 0.61) showed significant inverse association with depressive symptoms, when comparing the highest with the lowest quartile. Furthermore, the associations with anthocyanins and flavanones were in a dose-response manner. Other findings included inverse associations between depressive symptoms with quercetin, naringenin, and consumption of citrus fruit and wine, when comparing the highest to lowest quartiles. Although further studies are required to affirm these observed relationships, greater dietary intake of flavonoids may be inversely associated with depressive symptoms.

Through the use of food frequency questionnaires and factor analysis (to determine habitual dietary pattern), General Health Questionnaire (GHQ-12 [to measure psychological symptoms]) and a structured clinical interview (to assess depressive and anxiety disorders), Jacka et al. (2010) examined the extent to which high-prevalence mental disorders are related to habitual diet in 1,046 women aged 20-93 years (randomly selected from the population). After making adjustments in the factor analysis for age, socioeconomic status, education, and health behaviors, a "western" diet of processed or fried foods, refined grains, sugary products, and beer was associated with a higher GHQ-12 score. A “traditional” dietary habit (composed of vegetables, fruit, meat, fish and whole grains) was linked to lower risk of developing major depression or dysthymia (persistent depression) and anxiety disorders. There was also an inverse association between diet quality score and GHQ-12 score that was not confounded by age, socioeconomic status, education, or other health behaviors. Although these findings demonstrated an association between habitual diet quality and the high-prevalence mental disorders, additional studies are warranted.

This 2019 study investigated whether a Mediterranean-style diet (MedDiet) supplemented with fish oil can improve mental health in adults already suffering from depression (152 adults aged 18-65). Those who had self-reported depression randomly either: received fortnightly food hampers and MedDiet cooking workshops for 3 months and fish oil supplements for 6 months; or attended social groups every 2 weeks for 3 months. Out of the 95 who completed 3 months, the MedDiet group secured a higher MedDiet score, consumed more vegetables, fruits, nuts, legumes, wholegrains, greater variety in vegetables, fewer unhealthy snacks and red meat/chicken (all of these p-values were below 0.05, signifying statistical significance). With regards to depression, the MedDiet group reported a greater reduction in depression, and enhanced mental health QoL scores at the 3-month point. This improvement in mental health and diet were sustained for 6 months. There was a correlation identified between a drop in depression with greater MedDiet scores, increased consumption of nuts and more diversity in vegetables, while higher levels of omega-3 and decreased omega-6 were linked with improved mental health. Other mental health improvements had similar correlations, most notably for increased vegetable diversity and legumes. Parletta et al. believe this is one of the first randomised controlled trials to demonstrate healthy dietary changes are achievable and when supplemented with fish oils, can improve mental health in people with depression.

This robust French study (2018) examined whether adherence to the Mediterranean Diet (MD) was associated with incident depressive symptoms. The 3,523 participants taken from the SU.VI.MAX cohort had at least three dietary records at baseline during the first 2 years of follow-up, were free of depression at the start of the study, and had Centre for Epidemiological Studies Depression Scale (CES-D) data at the end of the follow up. Incident depressive symptoms (defined by CES-D score ≥17 for men and ≥23 for women) were seen in 172 individuals during the follow-up and were found to be associated with adherence to the rMED score in men (OR=0.91, p=0.03) after adjustments for potential confounders were made. This current study provided additional scientific evidence for the benefits of Mediterranean diet on health, with findings indicating that higher adherence to the Mediterranean Diet at midlife was associated with fewer incidental cases of depressive symptoms, especially among men.

Following evidence that gut microbiota can regulate brain function and that dysbiosis (imbalance of microbiota) in the intestines was related to anxiety, Yang et al. (2019) compiled evidence for the improvement of anxiety symptoms through the regulation of intestinal microbiota in the form of a systematic review. Of the 3,334 articles retrieved initially, 21 studies totalling1,503 subjects were included in this review following quality evaluation. 15 studies chose probiotics as interventions to regulate microbiota while the other 6 involved non-probiotic methods, such as adjusting daily diets. In the studies that used treatment as usual plus interventions regulating intestinal flora (IRIF) as interventions, two out of the five studies were found to be effective and used non-probiotic means of intervention (40% success rate) while 56% of the studies that used IRIF alone improved anxiety symptoms. When analysed further, those studies conducting non-probiotic interventions were 80% effective while 45% of studies that supplemented their subjects with probiotics were found to help with anxiety symptoms. To summarize, 11 out of the 21 studies (52%) included in this review were effective in reducing anxietal signs (5 using probiotic and 6 using non-probiotic interventions). Furthermore, the researchers observed 86% of the studies (6 out of 7) indicating that regulation of intestinal microbiota could treat anxiety symptoms. Although meta-analysis results are not available and more studies are warranted to confirm these findings, Yang et al. (2019) highlight that more than half of the studies demonstrated the positive effects of regulating intestinal microbiota in the treatment of anxiety symptoms and the higher efficacy of non-probiotic interventions compared to probiotics.

Pengpid and Peltzer (2019) collected data from 442 temple members with prehypertension and/or prediabetes (randomly selected from 12 Buddhist temples in Nakhon Pathom province in Thailand) to investigate the effect of fruit and vegetable consumption on mental health-related quality of life (QoL), major depressive disorder, and generalised anxiety disorders. In this longitudinal study, frequent vegetable consumption was in the fully adjusted model associated with better mental health-related quality of life (p=0.027) while frequent fruit consumption was not linked with a higher QoL. However in the unadjusted model, fruit and vegetable consumption was related to greater mental health-related QoL (p=0.033). In addition, more frequent fruit, vegetable, fruit and vegetable consumption did not significantly reduce the risk of major depressive and generalised anxiety disorder. Although there was no data linking frequent fruit and vegetable consumption with better mental health-related quality of life, regularly eating vegetables was associated with a better QoL.

Chatterton et al. (2018) collected data on and evaluated the cost-effectiveness of the SMILES trial, which previously demonstrated the efficacy of dietary changes via significant improvements in participants' Montgomery-Asberg Depression Rating Scale scores in the diet support group compared to a control group over 12 weeks. In the present study, participants were randomised into either seven sessions with a dietician for dietary support or an intensity matched social support (befriending) control condition. Evaluating the costs from health sector and societal perspectives, data on food and travel costs, medications, medical services, workplace absenteeism and presenteeism was collected using a resource-use questionnaire. Standard Australian unit costs for 2013/2014 were applied and incremental cost-effectiveness ratios (ICERs) were calculated as the difference in average costs between groups divided by the difference in average Quality Adjusted Life Years (QALY, the primary outcome of the SMILES trial). Compared with the social support condition, average total health sector costs were $856 lower and average societal costs were $2591 lower for those receiving dietary support. These differences were driven by lower costs arising from fewer allied and other health professional visits and lower costs of unpaid productivity. Although significant differences in mean QALYs were not found between groups, 68% and 69% of bootstrap iterations showed the dietary support intervention was dominant, meaning additional QALYs at a cheaper price, from the healthcare sector and societal perspectives. Therefore Chatterton and researchers (2018) found the dietary support intervention likely to be cost-effective as an adjunctive treatment for depression.

This 2014 paper measured the urinary redox potential of urine, which is a simple method for evaluating antioxidative status, with the aim to analyse the global antioxidative status and to correlate these findings with measures of anxiety and depression in 63 individuals (28 male, 35 females, ages 20-65). Normal anxiety state values corresponded to low urine redox potentials whereas higher anxiety states were associated with high urinary redox potential indicating high oxidative stress. It was also found that those with normal values in terms of the validated Beck Depression Inventory (BDI) questionnaire (used to assess anxiety and depression) had significantly lower urine redox potentials than individuals with higher BDI values. The results suggest that individuals with depression and anxiety are deficient in antioxidants, indicative of oxidative stress.

This 2020 study compared the lifetime prevalence of anxiety disorders among foreign-born and Canadian-born adults in middle and later life using data from the Canadian Longitudinal Study on Ageing (2010-2015). Of the 26,991 participants (49.3% men, 82.5% Canadian born, 58.5% aged 45–65 years) the overall prevalence of self-reported physician diagnosis of anxiety disorders was 8.5%, with immigrants being lower than Canadian-born respondents (6.4% vs. 9.3%, p < 0.001). After accounting for socio-economic, health-related, and nutritional covariates, the adjusted odds ratio (aOR) for anxiety disorders was lower among immigrants compared to those who were Canadian-born. The risk factors were identified as: younger age (aORs = 1.79–3.52), being a woman (aOR=1.25), single status (aOR=1.27), lower income (aOR = 1.28–2.68), multi-morbidities (aORs = 2.73–5.13), chronic pain (aOR = 1.31), lifetime smoking ≥ 100 cigarettes (aOR=1.35), BMI<18.5 (aOR=1.87), body fat ≥ 26% (aORs = 1.28–1.79), consuming <3 types of fruit and vegetable (aORs = 1.24–1.26), and pastry consumption >1/day (aOR = 1.55). The paper states that targeting socio-economic and nutritional risk factors may reduce the burden of anxiety disorders in middle and late adulthood.

Park, Kim, and Lee (2019) selected participants from a subset of the Korean Genome and Epidemiology Study to take part in this study investigating the association between dietary patterns and depression in middle-aged Koreans. Utilising the Korean version of the Beck Depression Inventory, participants who scored equal to or higher than16 were defined as having depression, while the subjects’ food intake over the year was determined using a validated semi-quantitative food frequency questionnaire. 448 of the 3,388 subjects in the study (13.2%) were identified as having depression. High consumption of vegetables, soybeans, mushrooms, seaweeds, white fish, shellfish, fruits and a low intake of white rice were characterised as the “healthy” dietary pattern, while the “unhealthy” dietary pattern was identified by high intakes of white rice, meats, ramen, noodles, bread, coffee and low consumption of rice with other grains. After adjusting for potential confounders, the subjects in the highest quartiles of the healthy dietary pattern had a significantly lower odds ratio of depression(OR=0.59, p = 0.0037) than those in the lowest quartiles. As well as this, the unhealthy dietary pattern was found to be negatively associated with depression (OR=1.65, p = 0.0021) among Korean adults. The study concluded that a healthy dietary pattern rich in mushrooms, soybeans, seaweeds, white fish, shellfish, vegetables, and fruit is associated with lower risk of depression while an unhealthy diet composed of ramen, meats, noodles, rice, bread and coffee is linked to the inverse.

This 2013 review summarises both the animal and human-based studies on the relationship between diet, exercise, and sleep (three significant mediators in the development, progression, and treatment of depression) with major depressive disorder, and their influence on dysregulated pathways associated with depression. These include neurotransmitter processes, immuno-inflammatory pathways, hypothalamic-pituitary-adrenal (HPA) axis disturbances, oxidative stress and antioxidant defence systems, neuroprogression, and mitochondrial disturbances. The authors call for more studies and mental health interventions on these aforementioned lifestyle factors associated with depression (including their effects on physiological processes) in order to expand our understanding and treatment of major depressive disorder.

This 2017 cross-sectional study assessed 3,846 adults from the general public in Isfahan, Iran, to investigate the association between adherence to a DASH-style diet and psychological health. DASH scores were created by focusing on 8 components (namely fruits, vegetables, nuts, legumes, dairy products, grains, sweetened beverages and sweets, sodium, and red and processed meats) to classify the participants into 3 categories: [low (≤40), moderate (41-50), and high adherence (≥51)]. Iranians with moderate adherence to the DASH diet were discovered to have the lowest rates of depression (OR = 0.73, p = 0.63) compared with those with low adherence. This link was significant in the stratified analyses for women and for normal-weight subjects. After controlling for potential confounding variables, inverse associations were observed between high adherence and anxiety in normal-weight individuals, and also between moderate adherence to the DASH diet and anxiety in those overweight or obese. A significant association could not be found between consumption of the DASH-style diet and psychological stress. Valipour et al. (2017) admit that further studies are required to confirm the inverse association between moderate adherence to DASH dietary pattern and depression.

This 2019 observational study compared the diets of depression sufferers and individuals without depression to assess the relationship between intakes of various food groups with depression. The food groups data the researchers took from the participants included legumes, nuts, whole-grain foods, chocolates, sweet foods, refined sugars, and vegetables and fruits. The diet of depressed individuals in this study had significantly lower levels of legumes, fruits, and vegetables but consisted of more sweets and refined sugars (p<0.05 for all comparisons). After adjustments were made for age and sex, depression was significantly associated with: no consumption of legumes (adjusted odds ratio [aOR] = 2.60); low intake of fruits and vegetables (aOR= 2.69); and high consumption of sweet foods and refined sugars (aOR = 1.91). Although Grases et al. (2019) note that conclusions cannot be drawn in terms of causality in this study and further research is required to check the causal relationships of the consumption of specific food groups with depression, and vice versa, this current study demonstrated that subjects without depression consumed more legumes, fruits and vegetables and had fewer sweets and pastries in their diets than those with depression.

Shafiee et al. (2018) conducted a large population-based, cross-sectional study examining the association between depression/anxiety symptoms with serum pro-oxidant-antioxidant balance (PAB) in 7,516 adults (62% female; 38% male; age 35-65). It was driven by the fact that depression and anxiety are significantly associated with inflammation, while inflammatory-related conditions are related to oxidative stress resulting from a disturbance in PAB. Serum PAB values increased incrementally across the four groups (none or minimal, mild, moderate, and severe depression) in both men and women (Ptrend < 0.001 among men and Ptrend = 0.005 among women). Analysing the data on anxiety, serum PAB values increased significantly across the four groups in men (Ptrend = 0.02) but not in women (Ptrend = 0.2). The adjusted odds ratios for serum PAB values among men with severe depression and anxiety symptoms were 1.75 and 1.27, respectively, while those among women were 1.40 and 1.17, respectively. It appears that depression and anxiety symptoms are associated with higher degrees of oxidative stress, expressed by greater serum PAB values.

Su et al. (2018) aimed to provide the first systematic review/meta analysis evaluating the association of anxiety symptoms with omega-3 polyunsaturated fatty acids (PUFAs). After searching for clinical trials assessing the anxiolytic effect of omega-3 PUFAs in humans (placebo-controlled and non-placebo) on numerous online databases, data was gathered on 1,203 participants with omega-3 PUFA treatment (mean age, 43.7 years; mean female proportion, 55.0%; mean omega-3 PUFA dosage, 1605.7 mg/d) and 1,037 participants without omega-3 PUFA treatment (mean age, 40.6 years; mean female proportion, 55.0%). An association was observed between clinical anxiety symptoms with omega-3 PUFA treatment compared with control arms, with subgroup analysis showing that the association of treatment with reduced anxiety symptoms was significantly greater in subgroups with specific clinical diagnoses than in subgroups without clinical conditions. The anxiolytic effect of omega-3 PUFAs was significantly better than that of controls only in subgroups with a higher dosage (at least 2000 mg/d) and not in subgroups with a lower dosage (<2000 mg/d). While additional well-designed studies will be needed, this review indicates that omega-3 PUFAs might help to reduce the symptoms of clinical anxiety.

Wallace & Milev (2017) set out to analyse the current research on the effects of probiotics on depressive symptoms since psychiatric disorders have been linked to changes in the gut microbiome, making it a potential target for novel antidepressant treatments. After systematically searching five databases, ten studies that met the inclusion criteria were analysed for effects on mood (5), anxiety (7) and cognition (3). The majority of the studies yielded positive results on all measures of depressive symptoms, but Wallace & Milev (2017) found that the strain of probiotic, the dosing, and duration of treatment varied widely. Furthermore, none of the studies assessed sleep. The authors agree that there is evidence for probiotics alleviating depressive symptoms but express the desire for additional double-blind randomised controlled trials in clinical populations to further assess efficacy.

This 2019 study investigated bidirectional associations between food groups and depressive symptoms in 1,058 Italian participants (aged 20-102 years) from the Invecchiare in Chianti study. Dietary intake, assessed with a validated FFQ, and depressive symptoms, measured with the Center for Epidemiologic Studies Depression scale (CES-D), were assessed at baseline and after 3, 6, and 9 years. Associations between intake of thirteen food groups and 3-year changes in depressive symptoms (and vice versa) were examined. Fish intake was inversely associated with CES-D score, whereas a higher sweet food intake correlated with a higher score for depressive symptoms. In the reverse direction, greater CES-D scores were associated with reduced intake of vegetables and of red and processed meat, in addition to an increase in dairy product intake and higher odds of eating savoury snacks. Fruit, nuts and legumes, potatoes, wholegrain bread, olive oil, sugar-sweetened beverages, and coffee and tea were not significantly associated in either direction. Although Elstgeest et al. (2019) admit that further trials are necessary to examine the causal associations between food groups and depression, this study supports the presence of bidirectional associations between food group intake and depressive symptoms.

Opie et al. (2020) drew data from the READI longitudinal study of socioeconomically disadvantaged Australian women to investigate the relationship between adherence to the Australian dietary guidelines and depressive symptoms. The risk of developing depressive symptoms was determined by the Centre for Epidemiologic Studies Depression (CES-D)) which was conducted at a 5-year follow-up on the 837 women included in the study. The study found an association between baseline diet quality (assessed using the Dietary Guideline Index [DGI-2013; score range 0 to 85) and depression, where a 10 unit increase in DGI-2013 score was associated with an estimated 12% reduction in risk of developing heightened depressive symptoms (RR = 0.875, p = 0.018). In addition, the fixed-effects model indicated that an increase in DGI score over 5 years follow-up was associated with a lower (improved) CES-D score. The results indicate that greater adherence to the Australian Dietary Guidelines may improve symptoms of depression, providing further support for dietary behavior change programs.

This 2020 review looked at available literature to outline the antidepressant mechanisms of probiotics and discuss their therapeutic potential in treating/managing depression. The use of probiotics has gained attention in recent years, according to Yong et al. (2020). Both human and animal studies have been conducted on this topic, some of which have implicated the involvement of a maladaptive microbiota-gut-brain (MGB) axis in the pathophysiology of depression. The physiological changes observed in some studies have led to the strategy of using probiotics to restore proper functioning of the MGB axis. Certain challenges have been identified, such as the heterogeneous nature of both the gut microbiota composition and depressive symptoms in the clinical setting. Despite this, the reviewers believe probiotics offer a number of advantages over standard pharmaceutical antidepressants, with regards to residual symptoms, side effects, and stigma.

The aim of this 2019 cohort study was to investigate the association between daily seaweed intake and depressive symptoms among 500 Japanese adults (ages 20-74). Seaweed consumption, which was measured using a self-administered diet history questionnaire, was used to divide the sample population into 3 groups according to changes in intake (decreased, unchanged, increased). Symptoms of depression were assessed using the Japanese version of the Self-Rating Depression Scale (SDS) and those scoring exactly 50 or higher were classified as showing depressive symptoms. The findings included 46 participants (9.2%) showing symptoms at the 3-year follow-up. Although multivariate analysis did not significantly associate consumption of seaweed with incidence of depression signs, the odds ratios for depressive symptoms were lower in the participants who had higher seaweed intake when compared to those who ate a lower amount of seaweed (decreased, 1.00; unchanged, 0.32 [0.13–0.81]; increased, 0.34 [0.13–0.88]; p for trend = 0.032) after adjusting for confounding factors.

Thus far, there has been limited research on populations with high fish consumption, and no research studies having used standard psychiatrist-based diagnosis of major depressive disorder (MDD), supporting the association between both fish consumption and levels of n-3 polyunsaturated fatty acids (PUFAs) with reduced depression risk. Matsuoka et al. (2017) investigated the relationship between dietary fish, n-3 PUFA, and n-6 PUFA consumption with risk of psychiatrist-diagnosed MDD in Japan. The study included 1,181 participants aged 63-82 years who completed food frequency questionnaires in both 1995 and 2000, also undergoing a mental health examination in 2014-2015. As well as diagnosing MDD in 95 patients, the researchers found a reduced risk of MDD in the third quartile for fish intake (111.1g daily, OR = 0.44), second quartile for eicosapentaenoic acid (EPA)(another n-3 PUFA)(307.7 mg per day, OR=0.54) and third quartile for docosapentaenoic acid (DPA) (123.1 mg per day, OR=0.42). ORs adjusted for cancer, stroke, myocardial infarction, and diabetes remained significant for fish and DPA intake. Matsuoka et al. (2017) conclude that moderate fish intake could be recommended for the prevention of MDD in aging Japanese adults.

Undertaken in Peru, this 2017 study aimed to evaluate the association between the consumption of fruits and/or vegetables (FV) with depressive symptoms. Using data from a population-based survey from 25 regions in Peru, the presence of depressive symptoms was determined according to the Patient Health Questionnaire (≥15 signified major depressive syndrome) while the 25,901 participants (mean age 44.2, 54% women) self-reported their intakes of FV. The results showed only 910 (3.8%) individuals reported consuming ≥5 servings of FV a day, and 819 (2.8%) people had depressive symptoms. Those in the lowest tertile of FV intake showed a greater risk of developing depressive symptoms (PR = 1.88) than those in the highest tertile. This association was stronger with fruits (PR = 1.92) than vegetables (PR = 1.42) alone. As well as discovering an inverse association between FV consumption with depressive symptoms, this study found that less than 5% of subjects ate ≥5 servings/day, the recommended number by WHO. This indicates the need to promote improved dietary patterns in order to potentially benefit mental health.

Taylor & Holscher (2018) summarised findings from clinical studies (found through a literature search) that used dietary interventions to improve depression, anxiety, or stress, as well as those on the role of gastrointestinal microbiota in these conditions. The results showed that mood was improved by enhancing diet quality, and that probiotic intake had beneficial effects on psychological or biological measures of depression, anxiety, or stress in individuals predisposed to a mood disorder. Bifidobacteria were enriched in subjects consuming ≥ 5 g/day. Fructooligosaccharide and galactooligosaccharide were found to improve anxiety and depression in participants consuming ≥ 5 g/day. Furthermore, the probiotics suppressed biological markers of stress in healthy individuals in a strain-dependent manner. The authors believe high-quality diets, prebiotics and probiotics may have positive effects on mood. They would like to see more research on probiotics’ influence on gastrointestinal microbiota, and the link between habitual diets rich in dietary fiber and omega-3-polyunsaturated fatty acids and risk of developing depression, anxiety, and stress.

This 2015 research paper used participants from the ‘supporting the modification of lifestyle in lowered emotional states’ (SMILES) trial to assess whether a healthy diet is affordable for a sample population with major depressive disorder. The first 20 subjects of the SMILES trial were invited to complete a 7-day food diary at baseline, the results of which were used in the cost analysis alongside the implementation of a modified Mediterranean diet (recommended for trial participants). The 20 people from the SMILES trial spent an estimated average of $138 per week on food and beverages for personal consumption, whereas for the recommended modified Mediterranean diet the estimated mean spend per person was $112. The modified Mediterranean diet at $1.54 per mega-joules (MJ) was cheaper per energy unit than the cost of the current dietary intake of the SMILES participants included in this study (at a mean of $2.35 per MJ). These findings suggest the healthy modified Mediterranean diet is cheaper than a poor quality diet, and highlights the possible need for public health messages getting the fact across that healthy eating does not exactly equal greater costs to a household, and that this strategy for selecting nutritious foods on a budget could support the achievement of desired dietary goals for preventing and managing chronic disease.

Since there were previously no dietary recommendations for depression, largely due to the recency of the nutritional psychology field, this 2017 study aimed to provide a set of practical dietary recommendations for the prevention of depression. It sought to use the best available current evidence, primarily to inform public health and clinical recommendations. Opie et al. (2017) found five key dietary recommendations from the published evidence: 1) Follow ‘traditional’ dietary patterns such as the Mediterranean, Norwegian, or Japanese diet; 2) Consume enough fruits, vegetables, legumes, wholegrain cereals, nuts and seeds; 3) Include many foods high in omega-3 polyunsaturated fatty acids in the diet; 4) Replace unhealthy foods with wholesome nutritious foods; and 5) Limit your intake of processed-foods, 'fast' foods, commercial bakery goods, and sweets. The researchers admit there were gaps in the scientific literature, but what they found suggests that a combination of healthful dietary practices may reduce the risk of depression. Opie et al. (2017) recommend being mindful of any protective effects that are likely to come from the cumulative and synergic effect of nutrients that comprise one's whole diet, rather than from the effects of individual nutrients or single foods.

Saneei and colleagues in 2016 published this study examining combinations of several lifestyle related factors related to depression and anxiety in a large group (3363) of middle age Iranian adults. A healthy lifestyle score was constructed by the use of data from dietary intakes, physical activity, smoking status, psychological distress and obesity while the components of the healthy lifestyle score were assessed using a dish-based 106-item semi-quantitative validated food frequency questionnaire (FFQ), General Practice Physical Activity Questionnaire (GPPAQ), General Health Questionnaire (GHQ) and other pre-tested questionnaires. In addition, the Hospital Anxiety and Depression Scale (HADS) was applied to screen for depression and anxiety. After adjustment for potential confounders, it was revealed that individuals with the highest score of healthy lifestyle were 95% less likely to be anxious (OR: 0.05) and 96% less likely to be depressed (OR: 0.04) compared with those with the lowest score. Moreover, non-smokers were less likely to suffer from anxiety (OR = 0.64) and depression (OR = 0.62) compared with smokers, and there was less probability that a person eating a healthy diet developed depression (OR = 0.71) than an individual with a non-healthy diet. Finally, individuals with low levels of psychological distress had expectedly lower odds of anxiety (OR: 0.13) and depression (OR: 0.10) than those with high levels. Saneei et. al (2016) found evidence among an Iranian population that healthy lifestyle score was associated with lower odds of depression and anxiety, and healthy diet, psychological distress and smoking status were independent predictors of mental disorders.

This 2019 comparative study aimed to investigate the depression risk associated with the Mediterranean-DASH diet intervention for neurodegenerative delay (MIND) diet and the Mediterranean diet (and their components). The 15,980 participants were adults free of depression at baseline or in the first two years of following up. At baseline, a validated food-frequency questionnaire was taken to measure food intake, and the median follow-up for depressive signs was 10.4 years. A total of 666 cases of incident depression was reported but no association could be found between incident depression and the MIND diet when comparing the highest to the lowest quartiles of adherence. Whereas, those subjects in the highest quartile for adherence to the Mediterranean diet were related to a lower risk of depression (hazard ratio = 0.75) with the link statistically significant, compared to those in the lowest quartile. Moreover, a drop in depression incidence correlated with high consumption of both fruits and nuts (HR = 0.82, p = 0.02), with moderate nuts consumption (HR = 0.77, p = 0.01), and most prominently with avoidance of fast/fried food (HR = 0.63, p = 0.03). No evidence of an association with the MIND diet was discovered but the Mediterrranean diet was related with reduced depression risk.

Among a Chinese population of 1,351, Xia et al. (2017) evaluated the relationship between dietary patterns and high depressive symptoms, using the Zung Self-Rating Depression Scale to measure manifestations of depression and define high depressive symptoms (score of 45+). The subjects were first matched with controls using the 1:1 ratio propensity score matching method. Next, dietary intake was assessed using a validated self-administered food frequency questionnaire. The study identified 3 dietary patterns that explained 25.1% of the total variance: the vegetables and fruits pattern; the sweets pattern; and the animal foods pattern. The subjects in the highest quartile of the vegetables and fruits pattern (also defined as a healthy pattern) showed fewer high depressive symptoms (OR = 0.65) compared to those in the lowest quartile. The sweets pattern and the animal foods pattern, however, correlated with increased prevalence of high depressive symptoms, with odds ratios of 1.33 and 1.79, respectively. The results reaffirmed the positive association between the sweets pattern and animal foods pattern with odds of high depressive symptoms. Other findings included a reduction in risk of depressive symptoms stemming from diets high in vegetables, fruits, soya bean products, and low in animal foods, candied fruits, cakes, ice cream, sugared beverages, and alcoholic drinks.

This 2016 study was conducted in Isfahan, Iran, in order to elucidate the relationship between major dietary patterns and prevalence of psychological disorders among a large sample of Iranian adults (3,846; aged 20-55). Dietary data was collected through a validated dish-based semi-quantitative food frequency questionnaire (FFQ), while participants' psychological health was examined by employing the Hospital Anxiety and Depression (HADS) scale. After adjusting for potential confounding variables, greater adherence to the lacto-vegetarian dietary pattern was associated with fewer incidences of depression among women (OR = 0.65). Moreover, when the top quintile within this dietary pattern was compared to the bottom quintile (among normal-weight subjects), the risk of developing anxiety was 39% lower. When looking at other dietary patterns, the traditional diet was related to greater occurrence of depression (OR was 1.42) and anxiety (OR = 1.56) among women, while the Western diet was linked with increased odds of depression in men (73% risk elevation) and also anxiety in normal-weight participants (OR = 2.05). Another significant trend observed was the increasing odds of psychological distress across higher quintiles of the fast food dietary pattern among women (p-value was 0.02). These results support consuming greater quantities of fruits, vegetables, low-fat dairy products and lowering intake of snacks, high-fat dairy products, chocolate, carbonated drinks, sweets, and desserts in order to decrease risk of psychological disorders.

This 2019 clinical trial focused on extra-virgin olive oil and whether its addition to the Mediterrranean diet can effectively reduce the recurrence of depression and improve its symptoms. The design was a two-arm, parallel-group study: arm 1 being the extra virgin olive oil-enriched Mediterranean diet; arm 2 being the control group without a modification. Dieticians kept in regular contact with the intervention group through web platforms or by phone, while psychiatrists and clinical psychologists conducted evaluations (semi-structured clinical interviews: Spanish SCID-I) to determine depression recurrence. Depressive symptoms were examined using the Beck Depression Inventory. Data was also collected on the participants’ quality of life, levels of physical activity, dietary habits, as well as their blood, urine, and stool samples. This data was collected at the start of the study and once in each of the following years. This clinical trial may be the first ongoing randomised clinical trial designed to assess the role of the Mediterranean diet in the prevention of recurrent depression. If proven to be effective, this could provide a cost-effective approach to avoid recurrence and improve quality of life.

Bishwajit et al. (2017) retrieved data of 13,133 adults from 3 South Asian countries (Bangladesh, India, and Nepal) and explored the relationship between fruit and vegetable (FV) consumption and depression. The subjects (3,262 from Bangladesh, 7,594 from India, 3,277 from Nepal), all aged 18 and over, took part in the World Health Survey conducted by the World Health Organisation (WHO). The outcome variables were self-reported depression (SRD) during the last 30 days and the last 12 months. During the past 12 months, depression was reported as 39% in Bangladesh, 17.7% in India, and 49.9% in Nepal. In India specifically, those who consumed fewer than five servings of vegetables per day were 41% and 57% more likely to report severe to extreme and mild to moderate depression (respectively) during the past 30 days, compared to those who consumed five servings a day. When comparing those who consumed at least 5 portions of fruit during the last 30 days, consumers of fewer than five servings a day were 248% and 45% more likely to report severe-extreme and mild-moderate SRD (respectively) in Bangladesh. Those belonging to this category of fruit consumption in Nepal were 191% and 42% more likely to suffer from the same levels of depression. It was concluded that daily intake of fewer than five portions of fruits and vegetables is linked with higher odds of depression. The team of researchers consider nutrition programs aimed at promoting FV consumption as possible modalities to improve depression rates in South Asia.

The aim of this 2020 systematic review was to evaluate the effects of polyphenols present in the Mediterranean diet on depressive symptoms. There has been speculation that the diet’s protective role in depression is related to its high polyphenol content. The systematic search for literature included both observational and experimental research on adults aged between 18 and 80 years, that assessed depression scores in relation to polyphenol intake. The 37 studies included (17 experimental, 20 observational) examined several polyphenols including those from tea, coffee, citrus, nuts, soy, grapes, legumes, and spices. The review found that 29 of the 37 studies demonstrated polyphenols having a statistically significant effect on depression, supporting the theory that polyphenols can alleviate depressive symptoms among adults.

Kontogianni et al. (2020) compared the effect of a high-polyphenol diet (HPD) to a low-polyphenol diet (LPD) on psychological well-being among the participants of the Polyphenol Intervention Trial (PPhIT). The trial involved the 99 subjects aged between 40-65 years with mild hypertension taking part in a four-week LPD washout period before being randomized to either a LPD or HPD for 8 weeks. Those who were assigned to a HPD reported a decline in depressive symptoms (assessed by the Beck Depression Inventory-II) and improvements in a couple of component scores (physical and mental health) assessed with 36-Item Short Form Survey. No differences in anxiety, stress, self-esteem or body image perception were observed but the findings suggested adoption of a high-polyphenol diet could potentially reduce depressive symptoms and enhance general mental health status as well as physical health in hypertensive patients.

Opie et. al (2018) here outlined the development of the prescribed diet [modified Mediterranean diet (ModiMedDiet)] for patients with major depressive disorders (MDDs) that was specifically designed for the SMILES trial [the first randomised controlled trial (RCT) exclusively designed to assess a dietary intervention, conducted by qualified dieticians, for reducing symptoms of depression in adults with clinical depression]. The data presented here marked the extent to which this intervention enhanced diet quality: the significant dietary improvements were found to be associated with changes in depressive symptoms. The SMILES trial recruited sixty-seven community dwellers from Melbourne, Australia all aged 18 and over, with poor quality diets and MDD. The ModiMedDiet was designed using a combination of existing dietary guidelines and scientific evidence from the emerging field of nutritional psychiatric epidemiology. The intervention in the trial consisted of seven individual nutrition counselling sessions conducted by a qualified dietician, while the control group involved a social support protocol with the same visit schedule and length as the nutritional counselling sessions. Opie et. al (2018) with the closing statement declared that the ModiMedDiet can be effectively implemented in clinical practice to manage major depression disorder.

While a high-lard diet is commonly used to induce obesity in animal model studies, at times leading to anxiety- and depression-like behaviors, Nakajima et al. (2020) identified the fact that there is limited data on the effect of changing dietary fat source on the behavior observed. This study treated Sprague-Dawley rats with varying types of high-fat (lard and olive oil) diet with high sucrose for more than 8 weeks, while monitoring anxiety-like behavior and cognitive function. Both the high-fat/high-sucrose diets tested led to a rise in body weight, adipose tissue, and serum leptin level. Anxiety-like behavior was seen in the group who received the high-lard/high-sucrose (HL/HS) diet but not in those rats consuming the high-olive oil/HS, diet. Moreover, the HL/HS diet induced an increase in glutamate transporters and decreased both glutamate receptor mRNA expressions in the prefrontal cortex, and serum lysophosphatidyl choline (LPC) conjugated with several fatty acids. The LPC specifically conjugated with eicosapentaenoic acid (EPA) was strongly associated with anxiety-like behavior, the study found. Thus, decreased concentrations of peripheral LPC conjugated with EPA and altered glutamate system in the prefrontal cortex may be implicated in the pathophysiology of anxiety-like behavior. The results suggested that rather than obesity, lipid composition may be the major cause of anxiety-like behavior in high-fat diet-induced obesity.

This 2017 preclinical study examined the relationships between body weight, high-fat diet (HFD), anxiety levels, and energy states among mice, with an additional aim of discovering whether the duration of exposure to the HFD has an impact on the anxiety-related behaviors. The mice were fed either a regular (RC) or HFD chow and were assessed on anxiety-related behaviors using behavioral tests such as the open field test (OFT) and the elevated plus maze. In order to test whether obesity phenotypes are associated with anxiety-related behaviors, the changes in behaviors observed through the OPF were analyzed alongside the alterations in body weight and glucose sensitivity after the mice were exposed to various levels of HFD and RC. The consumption of HFD were found to have a time-dependent biphasic effect on anxiety-related behaviors: showing less anxious behavior at 5 weeks compared with RC mice at the same stage of the intervention; at 8 weeks level of anxiety of both groups did not differ; and then at 15 weeks irrespective of type of feeding mice with metabolic symptoms of obesity exhibited more anxiety-related behaviors than those mice resilient to obesity phenotypes. The results suggested that HFD has a bidirectional influence on anxiety-related behaviors. Short-term exposure reduces anxiety, while longer exposure raises the anxiety of mice that present metabolic signs of obesity. The roles of both HFD and body weight in altering anxiety-like behaviors may overlap one another, which may be vital in explaining the relationship between HFD feeding and anxiety.

Sharma et al. (2012) designed this animal-model study on rats to assess the modifications in anxiety- and depression-like behavior and the alterations in substrates for brain plasticity and function induced by shifting diets from one that is rich in omega-3 fatty acids to one high in saturated fatty acids. Pregnant rats were fed with a healthy diet supplemented with omega-3 from their 2nd day of gestation period, while their pups were also initiated on this diet at 12-weeks old. The rats were then randomly selected to either continue with this same diet or switch to a high-fat diet (HFD) for 3 weeks. Their anxiety and depression-like behaviors were assessed using open field (OF) and elevated plus maze (EPM), while molecular examinations of the mice’s frontal cortex and hippocampus were also performed since these brain regions, when dysfunctioning, contribute towards stress and depression/anxiety-like behavior. The HFD appeared to increase anxious and depressive behaviors in the rats, backed up by the changes seen in the anxiety-related neuropeptide Y (NPY)-1 receptor. Also observed in the animals fed a 3-week HFD were reduced levels of brain-derived neurotrophic factor (BDNF), the BDNF signaling receptor pTrkB, and the BDNF signaling receptor pTrkB. A significant association was found between brain DHA contents with the levels of depression and anxiety-like behaviors shown by these rats. Thus DHA might help prevent the development of psychiatric disorders by building cognitive reserve, while the changes in n3/n-6 fatty acids taken in through diet may pose a risk for anxiety-like behaviors to arise.

While it is known that omega-3 polyunsaturated fatty acids (n-3 PUFA) can improve metabolic and mood decline by reducing inflammation, Demers et al. (2020) set out to determine the impact of n-3 PUFAs on energy homeostasis, anxiodepressive behavior, brain lipid composition, and gliosis in the diet-induced obese state. In this animal-model study, male C57Bl/6J mice were fed a saturated high-fat diet (HFD) or chow for 20 weeks, while also receiving fish oil [enriched with either control corn oil or a mixture of docosahexaenoic (DHA) and eicosapentaenoic acid (EPA) at equal ratios] during the last 5 weeks. During the final week of supplementation, behavior was assessed using tests such as the elevated-plus maze, light-dark box, and forced swim tasks. Gas chromatography-mass spectrometry and real-time PCR also allowed insight into the forebrain lipid composition and markers of microglia activation and astrogliosis in the mice. The glucose intolerance and reduced hyperphagia observed in the obese mice fed with HFD were corrected with 5 weeks of fish oil supplementation without affecting adipose mass. This supplementation also reduced depressive and anxious behavior, suppressed gene expression markers of brain reactive gliosis, and restored the levels of brain lipids that were depleted by the high-fat diet, particularly anti-inflammatory PUFA. Since supplementation with fish oil rich in EPA and DHA, given following a saturated HFD, corrected glucose intolerance, discouraged food consumption, suppressed anxiodepressive behaviors, enhanced anti-inflammatory brain lipids, and dampened indices of brain gliosis in obese mice, increasing dietary n-3 PUFA may be a helpful piece of advice to treat metabolic and mood imbalances associated with excess fat consumption and obesity.

The purpose of this 2020 study was to evaluate whether there are associations between long-term adherence to three diet quality scores, namely the Alternative Healthy Eating Index-2010 (AHEI-2010), Dietary Approach to Stop Hypertension (DASH) as well as the transformed versions of these scores, with the risk of recurrent depressive symptoms. Recchia et al. (2020) retrieved the data from the Whitehall II study (with 4949 participants), using outcomes from food frequency questionnaires to calculate diet scores, and defining those subjects who reported at least 2 episodes of depressive symptoms (examined by Center for Epidemiologic Studies Depression Scale and use of antidepressants) at the follow-up as having recurrent depressive symptoms. The food frequency questionnaires were conducted over 11 years between 1991/1993-2002/2004 whereas there were 4 periods of follow ups between 2002/04-2015/16. After adjusting for potential confounders, analyses showed higher scores on the AHEI-2010, DASH and tMDS were associated with lower incidence of recurrent depressive symptoms over the 13-year follow up, although no robust correlations were found for tMDS and DASH. Those participants who maintained a high AHEI-2010 score over the 11-year exposure period were 19% less likely to develop recurrent depressive symptoms compared to those who maintained a low AHEI score. Moreover, when compared to maintaining a high AHEI-2010 score, decreases in scores over time raised the odds of recurrent depressive symptoms by 34%. Long-term adherence to healthy diets defined by the Alternative Healthy Eating Index-2010 may support the prevention of recurrent depressive symptoms.

This 2019 article evaluated 3 theoretical diet quality indices [Mediterranean Diet Score (MDS), Alternative Healthy Eating Index (AHEI-2010) and Dietary Approaches to Stop Hypertension diet (DASH)] and determined whether each index was related with current depressive symptoms, short-term changes in depression, and with long-term history of depressive symptoms. The data used was from the Longitudinal Aging Study Amsterdam (LASA), which included assessments of depressive symptoms using the Center for Epidemiologic Studies Depression (CES-D) scale in 2014/2015 and at five regular 3-yearly cycles from 2001-2003 to 2015/2016. Whereas, the MDS, AHEI-2010 and DASH of the participants (aged >55 years) were derived between 2014-2015. Current depressive symptoms (CES-D ≥ 16) and history of depressive symptoms (CES-D ≥ 16 from 2001-2003 to 2011-2013) were both linked with lower MDS and AHEI scores in men only. Furthermore, chronic/recurrent depressive symptoms (CES-D ≥ 16 in both 2011-2013 and 2015/2016) correlated with lower MDS scores, while lower AHEI scores also tended to relate with chronic/recurrent depressive symptoms, compared to no depressive symptoms (twice CES-D < 16). Although prospective associations could not be made, these findings suggest that current and past depressive symptoms are associated with poorer diet quality, particularly in men, among this sample of middle-aged and older adults.

This 2020 systematic review, conducted methodologically as recommended by the Cochrane Collaboration and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, determined whether there are associations between red and processed meat consumption with depression (incident and prevalent) . The researchers scoured through the electronic databases MEDLINE, Embase and Scopus to gather the relevant papers published until March 2020. Following a critical appraisal, the review was left with 17 studies that met the inclusion criteria. Based on the data for the 241,738 participants, the overall effect size (ES) of depression for red and processed meat intake was 1.08 [(95% CI = 1.04; 1.12), p-value < 0.001]. The meta-analysis revealed a significant correlation between red and processed meat with risk of depression. These results may raise the awareness of the impact diet has on mental health.

This 2017 cross-sectional study assessed the relationship between diet quality and depressive symptoms in young (aged 18) and middle-aged (mean age 47·9) Japanese women. Sakai et al. (2017) employed diet history questionnaires and a diet quality score mainly based on the Japanese Food Guide Spinning Top. Of the 3963 young and 3833 middle-aged ladies, 22% and 16.8%, respectively, presented with depressive symptoms [determined as a Center for Epidemiologic Studies Depression (CES-D) score ≥23 and ≥19, respectively]. The female participants’ diet quality was positively associated with consumption of ‘grain dishes’, 'vegetable dishes', 'fish and meat dishes', 'milk' and 'fruits', and inversely related with energy intake from 'snacks, confection and beverages' and Na from seasonings. After making adjustments for potential confounders, the highest quintile for diet quality score had a 35% lower risk of developing depressive symptoms than the lowest quintile (OR=0.65), in the young female population (P=0.0005), while the variation between highest and lowest quintiles in the middle-aged women was larger (OR=0.59). Other analyses applying diet quality and CES-D scores as continuous variables also showed inverse associations. These results demonstrate the relevance of higher diet quality scores with lower incidences of depressive symptoms among young and middle-aged women in Japan, although back-up from prospective studies are warranted.

The aim of this 2020 study was to investigate the correlation between serum vitamin D concentrations and specific domains of depressive symptoms by each sex in the Korean general population. Rhee, Lee & Ahn (2020) retrieved data from the Korea National Health and Nutrition Examination Survey of 2014 to gather a sample size of 820 men and 916 women (aged 19-76) who had completed health interviews and health examinations thereby providing results for serum 25-hydroxyvitamin [25(OH)D] concentrations, the Patient Health Questionnaire-9 (PHQ-9), and certain covariates. A statistically significant association between log-transformed serum 25(OH)D concentrations and total PHQ-9 scores in men (incidence rate ratio [IRR] = 0.74) was identified after multiple covariate adjustments. In men, log-transformed serum 25(OH)D concentrations were significantly associated with the PHQ-9 cognitive/affective subscore (IRR = 0.56). The findings show serum vitamin D levels were inversely associated with cognitive/affective depressive symptoms in men.

In this 2020 study, 372 Chinese residents were assessed on their diet based on answers to the food frequency questionnaires distributed, and were examined on their depressive symptoms using the 9-item Patient Health Questionnaire (PHQ-9) score (a score >4 indicated presence of depressive symptoms). The objective set by Zhang et al. (2020) was to evaluate the relationship between the Chinese participants’ dietary patterns (determined from 30 food groups using factor analysis) with depressive symptoms. The four eating patterns, "vegetables-fruits," "traditional Chinese," "pastry-fruits," and "animal food", were identified and later analyzed. Adjusted models showed that compared to subjects who consumed the most animal products (belonging to the highest tertile animal food pattern) had greater risk of exhibiting signs of depression than those in the lowest tertile (OR = 2.08). This animal food pattern, which was already considered to be an unhealthy pattern, was demonstrated to be associated with increased risk of depression.

Nutritional therapies for mental disorders

Fruit and vegetable consumption and risk of depression: accumulative evidence from an updated systematic review and meta-analysis of epidemiological studies

The association of food quality index with mental health in women: a cross-sectional study

Sources of dietary fiber are differently associated with prevalence of depression

Low fruit and vegetable intake is associated with depression among Korean adults in data from the 2014 Korea National Health and Nutrition Examination Survey