Is Adult Onset ADHD a Valid Clinical Entity?

Several recent papers propose a paradigmatic shift in suggesting that childhood onset and adult onset ADHD are distinct syndromes. However, In these studies, adult onset ADHD was de novo only in the sense that full-threshold ADHD had not been diagnosed by the investigators at prior assessments. Most “adult onsets” of ADHD had neurodevelopmental roots, including subthreshold childhood ADHD. A multifactorial etiology of ADHD may lead to a wide variability in age at onset of initial symptoms, symptoms exceeding diagnostic threshold and impairment arising from those symptoms. This view of ADHD posits that symptoms and impairment emerge due to the accumulation of environmental and genetic risk factors. Those with lower levels of risk will take longer to accumulate sufficient risk factors and longer to onset with symptoms and impairment. This multifactorial perspective suggests that there is no clean separation of etiologic factors in people above and below the age of 12 proposed in DSM-5.