What Exactly Is Late-Onset ADHD?

Clinicians often face patients lacking childhood histories of attention-deficit/hyperactivity disorder (ADHD) who claim to have ADHD starting in adolescence or adulthood. These researchers examined longitudinal data on controls from a childhood ADHD treatment study to try to distinguish true late-onset ADHD from false positives, stimulant-seeking for cognitive enhancement, attentional difficulties owing to substance use or other mental illness, and childhood-onset ADHD simply identified later in life.

The 239 participants were initially screened and recruited as non-ADHD controls (baseline mean age, 10 years; 80% male; 67% white) and followed through mean age 24. They were assessed at least once in adolescence (ages, 12–17) and in adulthood …