Abstract
Adolescence is a key stage for identity formation. Attention deficit hyperactivity disorder (ADHD) is a lifelong neurodevelopmental condition that significantly affects adolescents' daily functioning and quality of life and plays an important role in shaping their identity. Illness identity refers to the extent to which a chronic diagnosis is integrated into an individual's self-concept. This study examined how ADHD symptom severity relates to diagnosis identity dimensions and health-related quality of life (HRQoL) in adolescents with ADHD. A cross-sectional study was conducted with 154 adolescents aged 11 to 18 years (M = 15.40, SD = 1.83). Participants completed validated measures of ADHD symptom severity, diagnosis identity (engulfment, rejection, acceptance, enrichment), and HRQoL. Statistical analyses included correlations, regression, and mediation models to clarify the relationships among these variables. Acceptance was significantly higher than other identity dimensions, while engulfment and rejection were lower. Higher ADHD symptom severity, especially inattention, was linked to greater engulfment. Engulfment predicted lower quality of life more strongly than symptom severity itself, and positive social experiences supported healthier identity integration. Mediation analysis showed that only engulfment significantly explained the link between symptom severity and HRQoL. Findings highlight the role of diagnosis identity, particularly engulfment, in the well-being of adolescents with ADHD. Interventions that combine symptom management with identity-focused approaches and social support may more effectively enhance adolescents' outcomes.