Late Onset ADHD? Usually Not

Primary care clinicians who work with adolescents and adults are seeing increasing numbers of patients presenting for an ADHD evaluation in which the symptoms didn’t develop until later in childhood or even in adulthood.  These “late onset” cases have traditionally been viewed as being atypical, although there has not been a great deal of systematic investigation.  This study from the well-known Multimodal

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Treatment Study of ADHD (MTA) takes advantage of their having a rigorously assessed group of individuals who were determined not to meet criteria for ADHD in childhood and examines in close detail the subset of individuals in this group who later present with symptoms of inattention and/or hyperactivity.

The MTA study was initially designed to examine pharmacological and non-pharmacological treatment for ADHD among children initially between 7 and 10 years of age.  As part of the study, a comparison group of 239 youth were also included who were not found to meet criteria for ADHD after a rigorous 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.

A total of 8.9% of the comparison sample that did not meet criteria for ADHD at baseline reported DSM-5 level of adolescent-onset ADHD symptoms with associated impairment.  Of these, 14% were judged to be due to heavy cannabis use, 24% attributed to other psychiatric disorders, and 33% only has symptoms in one setting. Excluding these individuals, a total of 2.9% of the original comparison sample had full ADHD symptoms with an adolescent onset and, with further follow-up, the majority of these individuals did not have symptoms that persisted into adulthood. With regard to adults, 4% of the comparison sample met ADHD criteria for symptoms and impairment with adult-onset with again substance use and other mental disorders accounting for a large proportion.  Indeed, only two subjects were deemed to have true adult-onset ADHD, and both had other significant mental health symptoms.  Putting it all together, about 95% of subjects who reported later onset ADHD symptoms were eventually excluded from the eventual diagnosis after careful assessment.

The authors conclude that the majority of what appear to be late-onset ADHD presentation are 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% statistic quoted for this study probably can’t be applied to the situation encountered in most clinicians’ day to day practice because everyone in this sample was carefully assessed in childhood and found not to meet criteria for ADHD.  In cases in which the primary care clinician has known a patient for many years and is confident that the person did not meet criteria for ADHD in childhood, a similar situation exists as is described in this study.  In many other cases, however, the patient’s behavior in childhood may be less known, raising the possibility that ADHD was present in childhood but that the diagnosis was missed.


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

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