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Study suggests child, adult ADHD are two distinct syndromes

Recent findings indicated distinct developmental trajectories between childhood and adulthood attention-deficit/hyperactivity disorder, suggesting that the theory that adulthood attention-deficit/hyperactivity disorder is a continuation of childhood attention-deficit/hyperactivity disorder is incorrect.

“The requirement of a childhood onset has always been a key criterion for the diagnosis of attention-deficit/hyperactivity disorder (ADHD) in adults, but recently this requirement has become surrounded by controversy,” Arthur Caye, of the Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil, and colleagues wrote.

To determine if adults with ADHD symptoms always have a childhood-onset disorder, researchers analyzed data from the 1993 Pelotas Birth Cohort Study for 5,249 individuals born in Pelotas, Brazil in 1993. Study participants were followed to age 18 or 19 years, with 81.3% retention. ADHD status at age 11 years was determined via the hyperactivity subscale of the Strength and Difficulties Questionnaire adjusted for a DSM-IV ADHD diagnosis based on clinical interviews with parents using the Development and Well-Being Assessment. At age 18 to 19 years, ADHD diagnosis was determined based on DSM-5 criteria.

At age 11 years, 8.9% of the cohort had childhood ADHD. At age 18 to 19 years, 12.2% of the cohort met DSM-5 criteria for young adult ADHD, except age at onset.

Prevalence of young adult ADHD decreased to 6.3% of the cohort when excluding comorbidities.

Compared with individuals without ADHD, those with childhood ADHD were more likely to be male (P < .001), while those with young adult ADHD were more likely to be female (P < .001).

Impairment was more common among participants with ADHD, as measured by traffic incidents, criminal behavior, incarceration, suicide attempts and comorbidities.

Approximately 17.2% of children with ADHD continued to have ADHD as young adults and 12.6% of young adults with ADHD had ADHD in childhood.

“Above all, our findings do not support the premise that adulthood ADHD is always a continuation of [childhood ADHD]. Rather, they suggest the existence of two syndromes that have distinct developmental trajectories, with a late onset far more prevalent among adults than a childhood onset. This finding would not mean that ADHD could not be conceptualized as a neurodevelopmental disorder,” the researchers wrote. “In both clinical practice and research, it is important to differentiate early- and late-onset disorders, and future investigations should test whether they have different pathophysiologic mechanisms, treatment response, and prognosis. In addition, patients with late-onset adulthood ADHD have clear impairments, and their clinical profile cannot account for only the effect of comorbidities.” – by Amanda Oldt

Disclosure: Caye reports no relevant financial disclosures. Please see the full study for a list of all authors’ relevant financial disclosures.