Attention-deficit/hyperactivity disorder (ADHD) is a common disorder characterized by inattention or hyperactivity–impulsivity, or both. For a long time, ADHD was thought of as a disorder of children which would sometimes persist into adulthood. DSM 5 uses as a criterion that several symptoms have to be present prior to age 12 years.

To discuss the findings of 3 recent cohorts that show the onset of ADHD in adulthood.

A review of selected articles of interest using PubMed database.

3 large, longitudinal, population studies from Brazil, New Zealand (NZ) and the United Kingdom (UK) show that we are at a crossroads in our understanding of ADHD. In each study, the prevalence of adult-onset ADHD (Brazil, 10.3%; UK, 5.5%; and NZ, 2.7%) was much larger than the prevalence of childhood-onset adult ADHD (UK, 2.6%; Brazil, 1.5%; and NZ, 0.3%). They all propose different conclusions that would result in a paradigmatic shift in ADHD: in Brazil, that child and adult ADHD are “distinct syndromes”; in the UK, “that adult ADHD is more complex than a straightforward continuation of the childhood disorder” and in NZ, that adult ADHD is “not a neurodevelopmental disorder”. Faraone et al., in an editorial in JAMA Psychiatry, propose that these findings might correlate to subthreshold child ADHD before it emerges as adolescent- or adult-onset ADHD.

It's an exciting time in ADHD research. These new data work as an incentive to study adult-onset ADHD and how it emerges. Future research will shape our understanding of adult ADHD.

The authors have not supplied their declaration of competing interest.