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Adult-Onset ADHD Is Usually Something Else

A new study finds that 95 percent of late-onset ADHD cases aren’t ADHD.

Among the many debates and questions that exist about Attention Deficit Hyperactivity Disorder (ADHD) is the question of whether or not its symptoms can begin in adolescence or even adulthood. With a few exceptions, like in cases of traumatic brain injury, the behaviors and thought patterns of ADHD are generally thought to be evident fairly early in childhood. Indeed, the official diagnosis of ADHD in DSM-5 requires that there be symptoms present in multiple settings before the age of 12. Despite these rules, many psychiatrists and other professionals who treat ADHD are seeing a noticeable rise in individuals who didn’t read the DSM and are seeking an evaluation for ADHD for symptoms that did not start until later in life.

To investigate this phenomenon more closely, a group of researchers took advantage of some relatively unique data that had been collected initially for a different purpose. The well-known Multimodal Treatment Study of ADHD (MTA) was designed in the 1990s to offer a rigorous look at the pharmacological and non-pharmacological treatment for ADHD among children initially between seven and 10 years of age. As part of the study, a comparison group was included of 239 youth who were not found to meet the criteria for ADHD after a thorough assessment in childhood. This group was followed into adolescence and adulthood using an assessment procedure that included rating scales, structured interviews, and examination of substance use.

As would be expected, some of the people in this group who were initially deemed not to meet the criteria for ADHD started experiencing problems with inattention and/or hyperactivity later in development and these folks were carefully evaluated. A total of 8.9 percent of the comparison sample that did not meet the criteria for ADHD at baseline reported DSM-5 level of adolescent-onset ADHD symptoms that included the presence of impairment from these symptoms.

After a more detailed examination, however, these symptoms were judged in 14 percent of them to be due to heavy cannabis use, while in another 24 percent the underlying cause seemed to be different psychiatric disorders. Furthermore, in 33 percent of the cases, the symptoms only were apparent in one setting.

Looking at cases of possible adult-onset ADHD, the same picture emerged with again substance use and other mental disorders accounting for a large proportion of what otherwise appeared to be adult-onset ADHD. Indeed, only two subjects were deemed to have true adult-onset ADHD and both had other significant mental health symptoms. Putting it all together, the authors calculated that 95 percent of subjects who reported later-onset ADHD symptoms did not actually have the diagnosis after careful assessment.

The researchers concluded that the majority of what appears to be late-onset ADHD is better accounted for by substance use, other psychiatric disorders, or non-impairing cognitive fluctuations. They advise very careful assessment of individuals who present with what appears to be late-onset ADHD.

While this study goes a long way to demonstrate that what may appear to be ADHD in adolescence and adulthood is often better accounted for by something else, it is important to point out that the 95 percent statistic quoted for this study probably can’t just be applied to the situation that most mental health professionals face with their evaluations because the people coming to be evaluated rarely had a comprehensive assessment that ruled out ADHD in childhood. People can present later in life with ADHD symptoms that, upon more careful examination, had been present all along. However, this study suggests that “pure” adolescent or adult-onset ADHD may be much less common than the raw numbers suggest.

More posts on some of the public controversies surrounding ADHD can be found here and here.


Sibley MH. et al. Late-Onset ADHD Reconsidered With Comprehensive Repeated Assessments Between Ages 10 and 25. Am J Psychiatry, epub ahead of print.

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