Research has raised the possibility of late-onset ADHD in young adults
Research published in JAMA Psychiatry this month has raised the possibility of late-onset attention-deficit/hyperactivity disorder (ADHD) in young adults
This goes against the traditional consensus that onset of ADHD only occurs in children.
The two studies, one from the UK and one from Brazil, showed that the majority of young adults with ADHD did not meet diagnostic criteria as children.
“[These studies] propose a paradigmatic shift in our understanding of ADHD,” said an accompanying editorial.
“They conclude, not only that the onset of ADHD can occur in adulthood, but that childhood-onset and adult-onset ADHD may be distinct syndromes.”
The UK study involved the evaluation of ADHD of 2,040 twins at ages 5, 7, 10, 12 and 18 according to DSM-IV diagnostic criteria in childhood and DSM-5 diagnostic criteria in young adulthood. The researchers fitted a twin model and identified a heritability estimate of ADHD symptoms of 35%.
Among the 166 individuals with adult ADHD, two-thirds (67.5%) did not meet the criteria for ADHD at any assessment in childhood.
In total, 247 individuals were diagnosed with ADHD as children, with 21.9% of these also meeting the diagnostic criteria as adults. Persistence of ADHD was associated with more symptoms during childhood and lower IQ in childhood.
“Our results suggest that adult ADHD is more complex than a straightforward continuation of the childhood disorder,” the researchers wrote.
At 18 years of age, the group with adult-onset ADHD differed from the group with persistent ADHD from childhood. Those that developed the disorder later had higher IQ than those with early-onset ADHD. They also had higher rates of alcohol dependence.
However, the two groups had similar life satisfaction, job preparedness and similarly elevated rates of anxiety disorder and marijuana dependence.
The Brazilian study assessed 5,249 individuals at age 11 and at age 18-19. Out of 60 young adults with ADHD, only 12.6% had the disorder in childhood.
Of the 393 children diagnosed with ADHD, only 60 (15.3%) continued to live with ADHD as young adults.
“These findings do not support the assumption that adulthood ADHD is necessarily a continuation of childhood ADHD,” the researchers wrote.
Both studies relied on self-reports by adults and reports from parents and/or teachers for children, which may have distorted the results, according to the accompanying editorial.
“It would be a mistake for practitioners to assume that most adults referred to them with ADHD symptoms will have no history of childhood ADHD,” the editorial warned.
The two research teams both considered the possibility that late-onset ADHD could be a distinct disorder to childhood onset ADHD.
In the UK study, this hypothesis was supported by the fact that the late-onset ADHD group showed different characteristics to the group with childhood-onset ADHD, including a dissimilar sex composition and lower heritability.
The Brazilian team concluded that their findings “suggest the existence of two syndromes with distinct developmental trajectories”.
JAMA Psychiatry, published online May 18
