Intellectual and Developmental Disorder (Intellectual Disability)

Intellectual developmental disorder (IDD), also termed intellectual disability, is a neurodevelopmental disorder characterized by significant limitations in both intellectual functioning and adaptive behavior, with onset during the developmental period. Limitations in intellectual functioning involve reasoning, problem solving, planning, abstract thinking, judgment, and academic and experiential learning, while adaptive behavior comprises conceptual, social, and practical skills (American Psychiatric Association, 2022). DSM-5-TR bases severity specifiers on adaptive functioning rather than IQ score alone, while the AAIDD 12th edition operationally defines the developmental period as before the individual attains age 22 (Schalock, Luckasson, & Tassé, 2021, AAIDD). It is important to note that feeding and eating disorders (including rumination disorder, pica, and ARFID) can co-occur with IDD and warrant additional clinical attention when severe.

In nutritional psychology, IDD is relevant because people with the condition commonly experience difficulties with chewing, drinking, and swallowing, dependence on assistance during meals, and nutrition-related behavior problems. These difficulties increase with severity of impairment and shape both nutritional status and the degree to which intake is caregiver-mediated rather than self-determined (Öztürk et al., 2024).