Many Young Adults with ADHD Did Not Have Childhood Diagnosis
Among a group of young adults with ADHD at age 18, many of them did not meet diagnostic criteria for ADHD at any assessment in childhood, according to a study by Louise Arseneault, Ph.D., of King's College London, and colleagues.
Among the 166 individuals with adult ADHD, 67.5 percent (112) did not meet the criteria for ADHD at any assessment in childhood. Analyses by the authors indicate that individuals with "late-onset" ADHD showed fewer externalizing problems and had higher IQ in childhood than those participants with persistent ADHD.
However, by young adulthood, participants with "late-onset" ADHD showed comparable ADHD symptoms and impairment, along with elevated rates of mental health disorders to those with persistent ADHD.
The authors also examined childhood predictors of ADHD persistence and remittance. They looked at functioning of participants with persistent, remitted (subsided) or late-onset ADHD to see how they compared. The study analysis included 2,040 participants from a cohort study of twins born in England and Wales.
The authors identified 247 individuals who met the diagnostic criteria for childhood ADHD; 54 (21.9 percent) also met criteria for the disorder at age 18. Persistent ADHD was associated with more childhood symptoms, lower IQ and, at age 18, those individuals had more functional impairment (school/work and home/with friends), generalized anxiety disorder, conduct disorder, and marijuana dependence compared with those whose ADHD had remitted, according to the results.
Study limitations include that diagnostic information on ADHD at age 18 was based only on self-reports. However, findings were corroborated by reports from co-informants.
"Further studies are needed to better understand the nature of the heterogeneity of the adult ADHD population. The extent to which childhood and 'late-onset' adult ADHD reflect different causes may have implications for research and treatment" the study concludes.
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Are Adult and Childhood ADHD 2 Syndromes?
In a related study, Luis Augusto Rohde, M.D., Ph.D., of the Hospital de Clinicas de Porto Alegre, Brazil, and coauthors examined data from 5,249 individuals who were born in Brazil in 1993 and followed up to ages 18 or 19. ADHD status was first determined at age 11 and again at age 18 or 19.
The authors report that at age 11, there were 393 individuals (8.9 percent) with childhood ADHD and 492 individuals (12.2 percent) at age 18 or 19 with young adult ADHD. The prevalence of young adult ADHD decreased to 256 individuals (6.3 percent) after comorbidities were excluded.
Among the 393 children with childhood ADHD, 60 (15.3 percent) continued to have young adult ADHD; 288 (73.3 percent) had no young adult ADHD in an assessment at 18 or 19 years old; and 45 (11.5 percent) were unavailable or lost to follow-up, according to the results. That resulted in a 17.2 percent persistence rate.
Among the 492 individuals with young adult ADHD, 60 (12.2 percent) had childhood ADHD; 416 (84.6 percent) did not have childhood ADHD; and 16 were not assessed at age 11 with a specific questionnaire, the results also show. Additionally, among the 256 participants with young adult ADHD without comorbidities, 29 (11.3 percent) had childhood ADHD; 220 (85.9 percent) did not have childhood ADHAD and seven (2.7 percent) were not assessed with a specific questionnaire at age 11. That resulted in a 12.6 percent prevalence rate of childhood ADHD among the young adult ADHD group.
The authors noted a number of study limitations.
"Above all, our findings do not support the premise that adulthood ADHD is always a continuation of C-ADHD [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. ... 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," the study concludes.
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Editorial: Can ADHD Onset Occur in Adulthood?
"In this issue of JAMA Psychiatry, two large, longitudinal, population studies from Brazil and the United Kingdom propose a paradigmatic shift in our understanding of attention-deficit/hyperactivity disorder (ADHD). 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. ... For researchers, these new data are a 'call to arms' to study adult-onset ADHD, determine whether and how to incorporate age at onset into future diagnostic criteria, and clarify how it emerges from subthreshold ADHD and other neurodevelopmental anomalies in childhood. The current age-at-onset criterion for ADHD, although based on the best data available, may not be correct. We hope that future research will determine whether and how it should be modified," write Stephen V. Faraone, Ph.D., of SUNY Upstate Medical University, Syracuse, N.Y., and Joseph Biederman, M.D., of Harvard Medical School, Boston.