This study examined which clinical factors (irritability, anxiety), cognitive-affective processes (emotion recognition, response inhibition, working memory, sustained attention), and negative thought patterns (external locus of control, negative cognitive style) mediate the path from ADHD to depression across childhood, adolescence, and young adulthood — and whether these pathways differ by sex — using two large longitudinal UK cohorts (ALSPAC and TEDS).
Combined mediators explained 30% (childhood), 48% (adolescence), and 29% (young adulthood) of the total ADHD-to-depression effect. Clinical factors (irritability, anxiety) were the most consistent mediators; negative thought patterns drove ~39–46% of mediated effects in adolescence. In young adulthood, indirect effects were detectable only in females (36%), while in childhood, males showed greater mediated effects (37%) than females (25%). Cognitive-affective factors showed no consistent mediation across development.
Sample sizes and cohort designs differed between ALSPAC and TEDS, limiting direct comparability. ADHD was measured via parent/self-report subscales (SDQ) rather than clinical diagnosis. Mediation models assume no unmeasured confounding, which cannot be guaranteed in observational data.
Screen children with ADHD for irritability and anxiety early, as these are the most consistent drivers of later depression across development. In adolescence, target negative thinking patterns (external locus of control, negative cognitive style) — especially in females, where these pathways persist into young adulthood.
