Growing up with ADHD: findings from an 18-year longitudinal follow-up study of adults with childhood ADHD, their siblings, and controls

BACKGROUND: The prevalent childhood-onset disorder attention-deficit/hyperactivity disorder (ADHD) (5-7%) poses risks for adult functioning, which should be identified with long-term prospective follow-up studies including a broad range of outcomes. METHODS: Differences in outcomes (measures of psychiatric status, behavioural/emotional problems, academic/professional functioning, adaptive functioning, neurocognition, physical health, healthcare service use) were investigated in an 18-year follow-up study of adults with childhood ADHD (n=154, M±SD age=27.4±3.7, 68% males), their siblings without childhood ADHD (n=138, M±SD age=29.6±4.4, 35% males), and controls (n=129, M±SD age=28.2±3.5, 40% males). Post-hoc tests investigated whether observed differences between the ADHD group and controls may be driven by a current ADHD diagnosis, by comparing persistent ADHD, remitted ADHD, and control groups. RESULTS: Childhood ADHD was related to worse functioning in adulthood on >60% of outcomes across all domains with small to large-sized effects (e.g., moderate/large differences in increased rates of ADHD and depression, externalizing problems, autistic traits, and worse neurocognitive outcomes). Siblings showed comparable functioning to controls. Persistent ADHD showed worse functioning on specific outcomes in the psychiatric, behavioural/emotional, adaptive, and physical health domains, as compared to remitted ADHD. Both ADHD groups had worse functioning compared to controls. CONCLUSIONS: Childhood ADHD increased the risk for worse functioning in adulthood. Siblings of the childhood ADHD group were not at risk for adverse outcomes. The current study identifies childhood ADHD as a risk condition for poorer long-term functioning, although substantial heterogeneity in outcomes across groups was noted. Heterogeneity within the childhood ADHD group seemed partly attributable to a current ADHD diagnosis.