Objective: Three recent prospective longitudinal studies of population cohorts reported nontrivial rates of "adult-onset" ADHD. Given that this result is at odds with the neurodevelopmental conceptualization of ADHD, as well as with general clinical experience, we obtained report of onset of symptoms in a clinical sample of adults diagnosed with ADHD.
Method: One hundred four adults diagnosed with ADHD completed retrospective ratings of DSM-IV/DSM-5 ADHD symptoms between the ages of 5 and 12 years.
Results: Fifty percent of the sample met full retrospective child diagnostic symptom criteria of six ADHD symptoms in either the inattentive or hyperactive-impulsive domains. Seventy-five percent met a less stringent criterion of four symptoms in either domain.
Discussion: These results are interpreted in light of a dimensional model of ADHD that posits emergence of ADHD symptoms and corresponding impairment as a function of increasing performance demands and/or decreasing environmental supports during the course of development.
Keywords: ADHD; Course; Late-Onset.