Adolescent attention-deficit/hyperactivity disorder and oppositional defiant disorder symptoms and educational and occupational outcomes. Longitudinal study in the Northern Finland Birth Cohort 1986

Adolescence is a crucial stage of life, during which the foundations for future education and career paths are built. This doctoral dissertation examined how symptoms of attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) at age 16 are associated with later educational attainment, employment, and income in adulthood. Yet, longitudinal evidence on their independent and combined effects on educational and labour-market outcomes, as well as the pathways through which they operate, remains limited.

The study was based on the Northern Finland Birth Cohort 1986, which includes more than 6,000 individuals. ADHD and ODD symptoms were assessed at age 16 using a questionnaire. Information on education, employment, sick leave, and income was obtained from national registers and followed up to around age 30.

The main finding was that adolescent ADHD symptoms, particularly when co-occurring with ODD symptoms, affected income at age 30 indirectly through reduced education and increased psychiatric comorbidity, rather than through direct effects. ODD symptoms alone were not associated with income. Both symptom dimensions were associated with higher unemployment and more sick-leave days in adulthood. The findings showed that adolescent ADHD and ODD symptoms were linked to poorer school performance already at age 16. Both symptoms increased the risk of not completing upper secondary or tertiary education. Those who had both ADHD and ODD symptoms in adolescence were in a particularly vulnerable position.

The results demonstrate that neurodevelopmental and behavioural symptoms in adolescence can have long-term consequences for life trajectories. Early identification and timely support in schools and healthcare services are essential to reduce later socioeconomic disadvantage.