MJB ADHD · Static reading view · Interactive version
Status: sourced · Content checked 2026-10-06
On average, the brain in ADHD matures on a later timetable, especially in prefrontal regions, with small differences in some deeper structures — largest in childhood.
Brain-imaging studies do not show an "ADHD brain" you could spot on a scan. They show average differences between large groups: the cortex reaches its peak thickness later, and some deeper structures are slightly smaller in childhood.
Across 824 scans of 223 children with ADHD and 223 controls, half of the cortex reached peak thickness by about 10.5 years in ADHD versus 7.5 years in controls; the delay was greatest in prefrontal regions that control attention and motor planning.
R4Pooling 23 sites (1, 713 people with ADHD, 529 controls), the accumbens, amygdala, caudate, hippocampus and putamen were slightly smaller on average (d −0.11 to −0.19); differences were largest in children, not significant in adults, and not explained by stimulant medication.
R3The pattern fits a developmental timing account: the same sequence of maturation, running later. Smaller differences in adults suggest partial catch-up for many people — while symptoms can persist, consistent with function depending on more than size.
Effect sizes of around 0.1–0.2 mean the two groups overlap almost completely. These are clues about mechanism, not tools for diagnosis.
Most large studies are cross-sectional; true lifespan trajectories need longitudinal data.