Optimal Functioning for Youth with Intellectual Disability: Conceptualizing and Measuring Thriving and Positive Mental Health

Abstract

Over recent decades, intellectual disability research has increasingly shifted from deficit-focused models toward positive psychology frameworks that emphasize strengths and positive functioning. However, limited research has examined broader constructs of optimal functioning, such as thriving and positive mental health. This is especially important to examine for youth with intellectual disability during the transition from childhood to adulthood, a period marked by elevated stressors and mental health problems. This dissertation addressed this gap by examining thriving as well as positive and negative mental health for youth with intellectual disability. The first study used a photo-elicitation qualitative design to develop a conceptualization of thriving for adolescents with intellectual disability, from the perspectives of youth and their caregivers. Participants completed semi-structured photo interviews using visual methods to enhance accessibility. Reflexive thematic analysis identified five interconnected thriving themes: Developing, Enjoying Life, Having a Positive Sense of Self, Connecting, and Mattering, with caregivers additionally emphasizing Being in a Safe and Supportive Environment. Thriving was conceptualized as experiencing these developmental processes shaped by youth-context interactions, even in the presence of challenges. The second study used a quantitative, multi-informant design with adapted youth self-report and caregiver-report measures to evaluate the applicability of the Two Continua Model for youth with intellectual disability. Analyses examined associations between positive mental health (emotional, psychological, and social wellbeing) and mental health problems. Across both youth and caregiver reports, positive mental health and mental health problems showed moderate-to-strong negative correlations, supporting the Two Continua Model premise that these constructs are related yet distinct rather than opposite ends of a single continuum. A substantial proportion of youth were classified as having flourishing mental health, despite co-occurring mental health disorders. Positive mental health was also uniquely associated with quality, rather than quantity, of relationships and community participation. Together, findings support the relevance of measuring mental health using a two continua framework and suggest that optimal functioning is best understood as high wellbeing alongside the ability to navigate challenges. This work provides a foundation for future research and clinical practice that integrates support for thriving processes with a dual-factor approach to mental health assessment and intervention.