ADHD can occur in adulthood and may be a syndrome distinct from childhood-onset ADHD, according to a new study.1
Researchers from the Institute of Psychiatry, Psychology & Neuroscience at King’s College London, led by Jessica C. Agnew-Blais, ScD, found that nearly 70% of young adults with ADHD did not meet criteria for the disorder at any of the childhood assessments. Adults with this “late-onset” ADHD had high levels of symptoms, impairment, and other mental health disorders.
The researchers suggested that “adult ADHD is more complex than a straight-forward continuation of the childhood disorder.” They published their results online in JAMA Psychiatry.
Another study published in the same issue from Brazil researchers also identified a large proportion of adults with ADHD as not having the disorder in childhood.2 Both the UK and Brazilian studies support previous findings from a New Zealand cohort.
The UK study included more than 2200 twins from the Environmental Risk (E-Risk) Longitudinal Twin Study. Symptoms of childhood ADHD were measured at the ages of 5, 7, 10, and 12 through mother and teacher reports. Young adults were interviewed at the age of 18 to assess ADHD symptoms and any associated impairments, as well as the existence of other psychiatric disorders.
The researchers also examined the genetic basis of ADHD in the twins. They found that adult ADHD was less heritable than childhood ADHD, and that having a twin with childhood ADHD did not lead to a higher risk of developing late-onset ADHD.
Two-thirds of the 166 individuals with adult ADHD did not meet criteria for ADHD at any assessment in childhood. Results from logistic regressions indicated that individuals with late-onset ADHD showed fewer externalizing problems and higher IQ in childhood compared with those with persistent ADHD.
There are some caveats in the study. Full-threshold ADHD had not been diagnosed prior to the assessments. Those in the adult-onset ADHD group had significantly elevated rates of ADHD symptoms, conduct disorder, and oppositional defiant disorder, so many of them appear to have had conditions with neurodevelopmental roots.
“We were very interested by this large ‘late-onset’ ADHD group, as ADHD is generally seen as a childhood-onset neurodevelopmental disorder. We speculated about the nature of late-onset ADHD: the disorder could have been masked in childhood due to protective factors, such as a supportive family environment. Or it could be entirely explained by other mental health problems. Alternatively, late-onset ADHD could be a distinct disorder altogether,” said Dr Agnew-Blais.1
“Although ADHD occurs in approximately 4% of adults, relatively few adults receive a diagnosis or treatment for the disorder. It is crucial that we take a developmental approach to understanding ADHD, and that the absence of a childhood diagnosis should not prevent adults with ADHD from receiving clinical attention.”1
The research brings up many questions about ADHD that arises after childhood. The researchers stated they will continue to search for how similar or different is “late-onset” ADHD compared with ADHD that begins in childhood, how and why late-onset ADHD arises, and what treatments are most effective for late-onset ADHD.
1. Agnew-Blais JC, Polanczyk GV, Danese A, et al. Evaluation of the persistence, remission, and emergence of attention-deficit/hyperactivity disorder in young adulthood. JAMA Psychiatry. Published online May 18, 2016. doi:10.1001/jamapsychiatry.2016.0465.
2. Caye A, Botter-Maio Rocha T, Anselmi L, et al. Attention-deficit/hyperactivity disorder trajectories from childhood to young adulthood evidence from a birth cohort supporting a late-onset syndrome. JAMA Psychiatry. Published online May 18, 2016. doi:10.1001/jamapsychiatry.2016.0383.