The Prevalence of Adult Onset ADHD, Reconsidered

Late-onset attention deficit hyperactivity disorder (ADHD) may not be valid in many adults presenting to clinics and false positive cases are more common than originally thought.

New data from Margaret Sibley (pictured), PhD, and colleagues suggests that more than 80% of participants that presented with ADHD symptoms in adulthood could have those symptoms explained by other factors. Despite appearing to have the condition and displaying symptoms similar to it, the symptoms could often be explained by problems such as psychological trauma, heavy marijuana use, or depressive symptoms.

While not a common condition, adult-onset ADHD is estimated to occur in 3% to 10% of adults, according to multiple large analyses. The childhood form of ADHD existed in roughly 10% of children, although some can “outgrow” it to a certain extent.

“Most late-onset cases displayed onset in adolescence and an adolescence-limited presentation,” Sibley, an associate professor of psychiatry & behavioral health at Florida International University’s Center for Children and Families and Herbert Wertheim College of Medicine. wrote. “There was no evidence for adult-onset ADHD independent of a complex psychiatric history.”

The investigators explored the complete longitudinal psychiatric histories in order to determine whether or not the symptoms being experienced by the participants were related to late-onset ADHD.

Symptoms of ADHD include poor organizational skills, fidgeting, becoming easily distracted, and forgetfulness. Sibley and the investigators examined 239 individuals that did not have childhood ADHD and administered 8 assessments from baseline (average age 9.89 years) to young adulthood (average age 24.40 years). Each participant was assessed once biennially between the ages of 10 and 25.

The diagnosis was determined by using parent, teacher, and self-reports of symptoms, substance abuse, impairment, and mental disorders, all considered within the context of when they were experienced. The data revealed that 95% of the individuals that originally screened positive on symptom checklists ended up being excluded from diagnosis. Most often, this was due to symptoms occurring as a result of heavy substance use.

"I believe many Adult ADHD patients have had it for a long time, perhaps even in childhood, but were not diagnosed until later," George Grossberg, MD, the director of geriatric psychiatry at Saint Louis University School of Medicine, told MD Magazine. "I do agree with one finding in the study - that ADHD-type symptoms may often be due to substance abuse. This always needs to be looking for."

Although a debated topic, the results of this study raised the question as to whether or not the condition exists at all. Sibley, in the study, advised that clinicians be cautious when administering assessment for ADHD in adults, stating that false positive cases are common without careful assessment.

“Recent birth-cohort studies support the notion of late-onset ADHD, but these investigations are limited by relying on screening instruments to assess ADHD, not considering alternative causes of symptoms, or failing to obtain complete psychiatric histories,” the authors noted.

The study was published in the American Journal of Psychiatry.