FRIDAY, Oct. 6 (HealthDay News) -- The age-at-onset criteria used to diagnose attention-deficit/hyperactivity disorder (ADHD) in adults may too strict, and those adults with ADHD have greater deficits in executive function associated with lower academic performance than adults who do not meet the criteria for ADHD, according to two studies in the October issue of the American Journal of Psychiatry.

In the first study, Stephen V. Faraone, Ph.D., of the State University of New York Upstate Medical University in Syracuse, studied 127 adults with childhood-onset ADHD who met all Diagnostic and Statistical Manual of Mental Disorders - Fourth Edition (DSM-IV) criteria, 79 adults with late-onset ADHD who met all other DSM-IV criteria except onset by 7 years of age, 41 adults with sub-threshold ADHD who did not meet all ADHD criteria, and 123 adults without ADHD. They found that the sub-threshold ADHD diagnosis was not valid, late-onset ADHD diagnosis was valid, and that the DSM-IV age-at-onset criteria was too strict.

In the second study, Joseph Biederman, M.D., from Massachusetts General Hospital in Boston, and colleagues examined executive function in 213 adults who met the DSM-IV criteria for ADHD and 145 adults who did not. They found that significantly more people with ADHD had deficits in executive function, which was associated with lower academic achievement, compared with adults who did not meet the criteria.