Despite the common assumption that adult ADHD is a childhood-onset neurodevelopmental disorder, the authors of this study state that no prospective longitudinal study has described the childhoods of the adult ADHD population. Accordingly, they report follow-back analyses of ADHD cases diagnosed in adulthood, alongside follow-forward analyses of ADHD cases diagnosed in childhood, in one cohort.
Study participants consisted of 1,037 individuals born in Dunedin, New Zealand, in 1972 and 1973 and followed to age 38, with 95% retention. Symptoms of ADHD, associated clinical features, comorbid disorders, neuropsychological deficits, genome-wide association study-derived polygenic risk, and life impairment indicators were assessed. Data sources were participants, parents, teachers, informants, neuropsychological test results, and administrative records.
Childhood ADHD was found to have a prevalence of 6% (predominantly male) and was associated with childhood comorbid disorders, neurocognitive deficits, polygenic risk, and residual adult life impairment. Adult ADHD had a prevalence of 3% (gender balanced) and was associated with adult substance dependence, adult life impairment, and treatment contact. Unexpectedly, the childhood ADHD and adult ADHD groups comprised virtually nonoverlapping sets; 90% of adult ADHD cases lacked a history of childhood ADHD. Also unexpectedly, the adult ADHD group did not show tested neuropsychological deficits in childhood or adulthood, nor did they show polygenic risk for childhood ADHD.
The authors concluded that adults presenting with ADHD may not necessarily have a childhood-onset neurodevelopmental disorder. They suggest that the disorder’s place in the classification system should be reconsidered, and future research should investigate the etiology of adult ADHD.
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Moffitt TE, Houts R, Asherson P, Belsky DW, Corcoran DL, Hammerle M, Harrington HL, Hogan S, Meier MH, Polanczyk GV, Poulton R, Ramrakha S, Sugden K, Williams B, Rohde LA, Caspi A: Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder? Evidence From a Four-Decade Longitudinal Cohort Study. Amer. J. Psychiatry [Epub ahead of print, May 22, 2015; http://dx.doi.org/10.1176/appi.ajp.2015.14101266 ]
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http://www.ncbi.nlm.nih.gov/pubmed/25998281