Adult Age at Diagnosis May Represent a Less Severe Phenotype Than Childhood Diagnosis

Adults who receive an ADHD diagnosis later in life may represent a somewhat less severe clinical subtype than those diagnosed in youth, but still experience impairment that warrants clinical attention, according to new data presented at American Professional Society of ADHD and Related Disorders (APSARD) 2026 Annual Conference.^1,2

Douglas Leffa, MD, PhD, a fourth-year psychiatry resident at the University of Pittsburgh, presented findings from a cross-sectional study leveraging a large US dataset to examine the clinical differences between individuals diagnosed with ADHD in youth and those first diagnosed in adulthood.

Leffa and colleagues examined data from the All of Us research program, a nationwide initiative that collects health information using multiple questionnaires. About 4.5% of the total sample size (N=298,091) had ADHD, with 3853 and 9674 participants receiving the diagnosis in youth and adulthood, respectively.

The data revealed interesting results, Leffa said. “What we saw was that those who were diagnosed in youth, they seemed to have a more severe clinical phenotype… They had more comorbidities, psychiatric and somatic comorbidities, plus more functional impairment in their daily life.”

Leffa and colleagues also measured the ADHD polygenic risk scores as an approximation for genetic liability. Their findings indicated patients who received an ADHD diagnosis in youth had an increased genetic liability.

Taken as a group, patients with ADHD regardless of age at diagnosis showed distinct characteristics. “When comparing [patients] with matched controls without ADHD, that's when we noticed that both ADHD groups presented clearly more comorbidities, more impairment, and more genetic liability, basically showing that when compared to controls, both were struggling and had the clinical characteristics that we would expect in ADHD,” Leffa explained.

Overall, the findings suggest that adult-diagnosed ADHD may represent a less severe presentation, but one that remains clinically significant. Individuals diagnosed later in life were “slightly less severe based on our parameters,” Leffa said, yet still had sufficient impairment, indicating that they would potentially benefit from management, he added.

For more conference news from APSARD, visit our conference coverage page.

References

1. Leffa D. Clinical differences between adults diagnoses with ADHD in childhood versus adulthood: a cross-sectional study from the All of Us Research Program. Presented at the American Professional Society of ADHD and Related Disorders (APSARD) 2026 Annual Conference; January 15-18, 2026; San Diego, CA.

2. Leffa D. Poster Data Blitz. Presented at the American Professional Society of ADHD and Related Disorders (APSARD) 2026 Annual Conference; January 15-18, 2026; San Diego, CA.