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, 172 (10), 967-77

Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder? Evidence From a Four-Decade Longitudinal Cohort Study

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Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder? Evidence From a Four-Decade Longitudinal Cohort Study

Terrie E Moffitt et al. Am J Psychiatry.

Abstract

Objective: Despite a prevailing assumption that adult ADHD is a childhood-onset neurodevelopmental disorder, no prospective longitudinal study has described the childhoods of the adult ADHD population. The authors report follow-back analyses of ADHD cases diagnosed in adulthood, alongside follow-forward analyses of ADHD cases diagnosed in childhood, in one cohort.

Method: Participants belonged to a representative birth cohort 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. Adult ADHD diagnoses used DSM-5 criteria, apart from onset age and cross-setting corroboration, which were study outcome measures.

Results: As expected, childhood ADHD had a prevalence of 6% (predominantly male) and was associated with childhood comorbid disorders, neurocognitive deficits, polygenic risk, and residual adult life impairment. Also as expected, 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.

Conclusions: The findings raise the possibility that adults presenting with the ADHD symptom picture may not have a childhood-onset neurodevelopmental disorder. If this finding is replicated, then the disorder's place in the classification system must be reconsidered, and research must investigate the etiology of adult ADHD.

Conflict of interest statement

Conflicts of interest: TM, RH, DB, DC, MH, HH, SH, MM, RP, SR, KS, BW, and AC have no conflicts of interest to report.

Figures

Figure 1
Figure 1
Childhood-ADHD and adult-ADHD groups comprised virtually non-overlapping sets.
Figure 2
Figure 2
The adult-ADHD and child-ADHD groups did not overlap. This was not simply because many childhood-ADHD cases just missed the 5-symptom threshold for adult diagnosis. Panels a and b show how many childhood-ADHD cases (N = 61) had each level of adult-ADHD inattention and hyperactive/impulsive symptoms. For comparison, panels c and d show how many adult-ADHD cases (N = 31) had each level of adult symptoms. (3 individuals who had ADHD as a child and as an adult are included in all graphs.) * 2 Study members with current schizophrenia at age 38 were excluded from the adult-ADHD diagnosis, per DSM5.
Figure 3
Figure 3
Few adult-ADHD cases had childhood onset before age 12 years. We used the available items rated by teachers at child ages 5, 7, 9, and 11: “very restless, often running about or jumping up and down, hardly ever still,” “squirmy fidgety child,” “poor concentration, short attention span.” Items were rated 0=does not apply, 1=applies somewhat, or 2=certainly applies, yielding a range from 0 to 6. Ratings were summed at each age, then averaged across ages 5, 7, 9, and 11. Panel a shows few adult-ADHD group members (N = 31) scored at least one symptom rated “2=certainly” by their teachers. For comparison, panel b shows that most childhood-ADHD group members (N = 61) scored more than one symptom rated “2=certainly.” (3 individuals who had ADHD as a child and as an adult are included in all graphs.)

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