Representativeness of participants in a clinical trial for attention-deficit/hyperactivity disorder? Comparison with...

Clinical trials have demonstrated that pharmacotherapies can safely treat attention-deficit/hyperactivity disorder (ADHD) in adulthood. Eligibility criteria in these trials may significantly limit their external validity by excluding a significant portion of adults with ADHD in the general population. In particular, exclusion criteria may frequently exclude individuals with comorbid mental health conditions, which are common in the adult ADHD population.

We addressed the representativeness of clinical trials by comparing 146 adult clinical trial participants with DSM-IV ADHD and a community sample composed of 124 adults with DSM-IV ADHD and 123 non-ADHD controls. Subjects were compared on socioeconomic status, Hollingshead occupational code, cognitive measures, lifetime psychopathology, and Global Assessment of Functioning (GAF) scale ratings.

Adults with ADHD in the community sample had higher rates of lifetime psychiatric comorbidity, lower GAF scores, and lower occupational codes than those in the clinical trial. The clinical trial eligibility criteria would have excluded 61% of community sample adults with ADHD. This excluded portion of the community sample had higher rates of lifetime psychiatric comorbidity and lower GAF scores than clinical trial participants.

Adults with ADHD participating in the clinical trial had less evidence of functional impairment and endorsed less psychiatric comorbidity than the majority of community sample subjects with ADHD. This suggests that findings from clinical trials may have limited external validity for adults with ADHD in the general population, particularly for those adults with ADHD with the greatest burden of comorbid psychopathology.