When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.
Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.
The overarching aim of this thesis was to examine how the characteristics the social environment of youth with intellectual disabilities (ID) could contribute to their risk of psychopathology. The first study investigated the nature of the social interaction profiles observed among youth with ID, defined while considering their relationships with their parents, peers, and teachers, as well as the implication of these profiles for their self-esteem, aggressive behaviors, and prosocial behaviors. A sample of 393 youth with mild (48.2%) to moderate (51.8%) levels of ID, aged between 11 and 22 (M=15.70), was recruited in Canada (n=141) and Australia (n=253). Our results revealed four profiles, corresponding to Socially Isolated (23.24%), Socially Integrated (39.83%), Socially Rejected (28.37%) and Socially Connected (8.57%) youth with ID. The socially integrated and connected profiles both presented higher self-esteem, more prosocial behaviors, and less aggressive behaviors than the socially isolated and rejected profiles. The second study investigated associations between initial levels and changes in the quality of the relationships youth with intellectual disabilities (ID) share with their parents and teachers and changes in their levels of depression over time. A sample of 395 youth with mild (48.3%) and moderate (51.7%) ID, aged between 11 and 22 (M=15.69), were recruited in Canada (n=142) and Australia (n=253). Youth completed self-report measures of relationship quality and depression twice over a one-year period. Initial levels of warmth (β=-.109) and conflict (β=-.302) predicted decreases in depression. Increases in warmth predicted decreases in depression (β=-.179), while increases in conflict predicted increases in depression (β=.268). Discrepancies between youth relationships with their parents and teachers predicted decreases in depression (βwarmth=-.732; βconflict=-.608). The third and final study investigated how school experiences and personal characteristics of youth with ID contributed to their longitudinal trajectories of anxiety. To this end, we relied on a sample of 390 youth with mild (48.2%) to moderate (51.8%) levels of ID, aged from 11 to 22 (M=15.70), and recruited in Canada (n=140) and Australia (n=250). Across three yearly time points, all participants completed self-report measures of anxiety, school climate, and victimization. Our results revealed a slight normative decrease in anxiety over time and showed that experiences of school victimization were associated with higher levels of anxiety (initially and momentarily) and increases in victimization were accompanied by increases in anxiety over time. Perceptions of attending a school that fosters security and promotes learning also tended to be accompanied by lower levels of anxiety (initially and momentarily). Momentary increases in perceptions of attending a school that fosters positive peer interactions were associated with momentary decreases in anxiety, whereas momentary increases in perceptions of attending a school characterized by positive teacher-student relationships and an equitable treatment of all students both led to small momentary increases in anxiety once all other components of student school experiences were considered. All together, our results highlight important targets for intervention in ensuring better psychological adjustment and future avenues for research on youth with ID.