Adult ADHDAdult ADHD May Be Distinct From Childhood ADHD

Attention-deficit/hyperactivity disorder (ADHD) in children may be distinct from and unrelated to ADHD in adults, according to a study in the American Journal of Psychiatry.

It is long been understood that adult ADHD is the natural extension of childhood onset ADHD. In other words that adults with ADHD began as children with ADHD. In fact ADHD is currently listed in a chapter of disorders of cognition that first present in childhood in the Diagnostic and Statistical Manual (DSM).

It was so much embedded in the assumed nature of reality, that the DSM-5 ADHD and Disruptive Behavior Disorders Work Group asserted that “ADHD begins in childhood” and proceeded to provide formal criteria for the diagnosis of ADHD in older adolescents and adults using the same items as are applied in children, including the requirement that symptoms show up in childhood…

Remarkably, there was never, until now, a prospective longitudinal study that looked at the childhoods of adults with ADHD…. Ooops.

In this study, the researchers followed a birth cohort of 1,037 individuals born in Dunedin, New Zealand, in 1972 and 1973 until age 38. A number of factors were assessed, including symptoms of ADHD, associated clinical features, comorbid disorders, neuropsychological deficits, genome-wide association study-derived polygenic risk, and life impairment indicators.

As the researchers had 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% (with his many females as males affected) and was associated with adult substance dependence and adult life impairment.

However, the researchers were surprised to find that 90% of adult ADHD cases had never had a history of childhood ADHD. In addition the adult ADHD group did not show neuropsychological deficits in childhood, nor did they have the genetic risk factors for childhood ADHD.Childhood and Adulthood ADHD

Here is a way of visualizing the data –

Of all of the participants of the study, 6% had childhood ADHD. But only about 1 in 5 of those went on to have adult ADHD. On the other hand, the vast majority (90%) of those with adult ADHD had no evidence of ever having had childhood ADHD or even risk factors for childhood ADHD.

The researchers concluded that, if the study findings are replicated, Adult ADHD needs to be considered a separate disorder, in many cases, from childhood ADHD.

And I guess we’re going to have to study what causes it and how to treat it…

References

Moffitt TE, Houts R, Asherson P, et al: Is adult ADHD a childhood-onset neurodevelopmental disorder? Evidence from a four-decade longitudinal cohort study. Am J Psychiatry 2015;172:967977

Moffitt TE, Houts R, Asherson P, et al: Is adult ADHD a childhood-onset neurodevelopmental disorder? Evidence from a four-decade longitudinal cohort study. Am J Psychiatry 2015;172:967977

F. Xavier Castellanos Is Adult-Onset ADHD a Distinct Entity? American Journal of Psychiatry 2015 172:10, 929-931