Attention Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder associated with persistent functional impairments across the lifespan. Research shows that social impairments, including difficulties in building and maintaining relationships are amongst the most debilitating aspects of the condition, associated with adverse outcomes across the lifespan. Social difficulties represent a particular source of suffering during adolescence, a time when young people seek peer acceptance and construct a sense of social identity. Yet, factors underlying social impairments in youths with ADHD remain unclear.

The broad objective of this PhD thesis was to elucidate self- and other-oriented psychological processes that may underly social impairments in adolescents with ADHD, focusing on two key processes essential for self-regulation in interpersonal contexts: 1) emotion regulation, including its subserving processes of emotion recognition, emotion recognition and the use of cognitive emotion regulation strategies and 2) mentalizing, the ability to interpret one’s own and other’s behavior in terms of intentional mental states. Adopting a dimensional approach, four cross-sectional studies were designed to explore the associations between the continuum of ADHD symptoms and individual differences in emotion regulation and mentalizing.

Study 1 explored the contributions of emotion regulation processes to self-reported functional impairment scores in 161 community adolescents on the continuum of ADHD symptoms. Results demonstrated that emotion reactivity and the use of maladaptive cognitive emotion regulation strategies emerged as major sources of perceived social and self-concept difficulties, beyond the effects of core ADHD symptoms and executive control.

Study 2 compared performance on measures of emotion recognition, emotion reactivity and cognitive emotion regulation in 40 adolescents with ADHD and 40 healthy controls. Results showed that adolescents with ADHD reported using less adaptive cognitive emotion regulation strategies. Moreover, in youths with ADHD, emotion dysregulation predicted adolescent-ratedfunctional impairment scores, whereas parent-rated functional impairments were predicted by symptom severity and comorbidity status.

Study 3 explored the emerging hypothesis that inattention symptoms may show unique associations with mentalizing in 89 community adolescents. Using a dynamic computerized mentalizing task (Movie for Assessment of Social Cognition, MASC), we demonstrated that inattention symptoms were negatively associated with mentalizing and more specifically, with the ability to mentalize about cognitive mental states.

Study 4 analyzed mentalizing performance on the MASC in 26 adolescents and 23 young adults with ADHD as well as age-and gender-matched healthy controls. Results showed a tendency to hypomentalize in adolescents with ADHD, that was correlated with the severity of attention problems. This pattern of results was however not found for adults with ADHD.

Overall, our findings 1) provide support for the critical role of emotion regulation in adolescent- reported social difficulties, both in typical development and in ADHD and 2) provide original empirical evidence linking inattention symptoms to hypomentalizing patterns in adolescents with ADHD.