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Childhood ADHD diagnosis does not always precede adult ADHD

Recent findings showed a significant proportion of individuals with late-onset attention-deficit/hyperactivity disorder did not meet criteria in childhood, suggesting that a lack of a childhood diagnosis should not preclude late-onset diagnosis in adulthood.

“To date, adult attention-deficit/hyperactivity disorder (ADHD) has been conceptualized as a continuation of childhood ADHD. However, recent findings have suggested that, for some individuals, ADHD may not arise until adolescence or adulthood and may be associated with different risk factors and outcomes than childhood ADHD,” Jessica C. Agnew-Blais, ScD, of King’s College London, and colleagues wrote.

To evaluate childhood risk factors and young adult functioning of individuals with persistent, remitted and late-onset adult ADHD, researchers assessed a nationally representative birth cohort from the Environmental Risk Longitudinal Twin Study of 2,232 twins born in England and Wales from 1994 to 1995. Childhood ADHD was evaluated at ages 5, 7, 10 and 12 years. ADHD symptoms and associated impairment, overall functioning and other mental health disorders were examined at age 18 years.

Overall, 247 study participants met diagnostic criteria for childhood ADHD. Of these, 21.9% met criteria for ADHD at age 18 years.

Persistence was associated with more symptoms (OR = 1.11; 95% CI, 1.04-1.19) and lower IQ (OR = 0.98; 95% CI, 0.95-1).

At age 18 years, participants with persistent ADHD had more functional impairment at school or work (OR = 3.3; 95% CI, 2.18-5) and at home or with friends (OR = 6.26; 95% CI, 3.07-12.76), generalized anxiety disorder (OR = 5.19; 95% CI, 2.01-13.38), conduct disorder (OR = 2.03; 95% CI, 1.03-3.99) and marijuana dependence (OR = 2.88; 95% CI, 1.07-7.71), compared with those with remitted ADHD.

Of the 166 participants with adult ADHD, 112 (67.5%) did not meet criteria for ADHD at any childhood assessment.

Logistic regressions analysis indicated participants with late-onset ADHD exhibited fewer externalizing problems (OR = 0.93; 95% CI, 0.91-0.96) and higher IQ (OR = 1.04; 95% CI, 1.02-1.07) in childhood, compared with those with persistent ADHD.

However, ADHD symptoms and impairment and rates of mental health disorders at age 18 years were comparable between participants with late-onset ADHD and those with persistent ADHD.

“Our findings highlight the importance of taking a developmental approach to understanding ADHD. Although many questions remain regarding the nature of late-onset ADHD, this group showed significant levels of ADHD symptoms and impairment, as well as poor functioning and high rates of psychiatric comorbidity. Therefore, the absence of a childhood diagnosis of ADHD should not preclude adults with ADHD from receiving clinical attention,” the researchers wrote. “Whether individuals with late-onset vs. childhood-onset ADHD respond differently to treatment is an open question, and further research is required to better understand the causes, course, and optimal treatment of late-onset ADHD.” – by Amanda Oldt

Disclosure: The researchers report no relevant financial disclosures.