Studies Look at ADHD in Adults

A new study, led by a team of British researchers, looked at young adults with ADHD and found that a significant number of these individuals did not exhibit symptoms in childhood as required by the definition of ADHD in the The Diagnostic and Statistical Manual of Mental Disorders, (DSM-V), from the American Psychiatric Association. 

The DSM-V definition of ADHD requires that the individual have:

Six or more persistent symptoms of inattention and/or hyperactivity-impulsivity, several of which were present prior to 12 years of age, that interferes with functioning or development, which are present in two or more settings (eg. at home and at school or at work), and which interfere with social, academic, or occupational functioning.

The researchers looked at a subset of more than 2,000 individuals as part of a study of twins, and found that adults with ADHD included both those who had "childhood onset" ADHD that persisted into adulthood and those who did not meet the DSM requirements for ADHD in childhood but who met them (absent the age of onset) in adulthood. Specifically, they found that, "among 166 individuals with adult ADHD, 112 (67.5%) did not meet criteria for ADHD at any assessment in childhood." 

The British researchers noted differences between the childhood and adult onset groups in areas such as severity of symptoms and comorbid mental health conditions and suggested that more research is needed to determine the relationship between these two types of ADHD and whether they are really the same disorder.

A second study, this one led by Brazilian scientists and published in the same journal as the British study, led researchers to conclude that their findings did " not support the assumption that adulthood ADHD is necessarily a continuation of childhood ADHD. Rather, they suggest the existence of 2 syndromes that have distinct developmental trajectories."

As the British research team noted, "the extent to which childhood-onset and late-onset adult ADHD may reflect different causes has implications for genetic studies and treatment of ADHD."