Prevalence of DSM-IV symptoms of ADHD in adult licensed drivers: Implications for clinical diagnosis

The present study reports on the prevalence of the DSM-IV symptoms for attention deficit hyperactivity disorder (ADHD) in a sample of 720 adults applying for or renewing their driver's licenses in central Massachusetts (ages 17-84 years). Symptoms were assessed using two self- report rating scales: One for current symptoms and a second for retrospective recall of child hood symptoms (ages 5-12 yrs.). Three age groups were created: 17-29, 30-49, and 50+ years. All scores and symptom counts for both scales declined significantly with age for both disorders. Males and females did not differ significantly on scores for current symptoms. However, for recall of childhood symptoms, males obtained higher scores than females. Requiring that DSM-IV diagnostic thresholds be met for both current and childhood symptoms, the prevalence of adult ADHD was found to be 1.3% for the Inattentive Type, 2.5% for the Hyperactive-Impulsive Type, and 0.9% for the Combined Type. The prevalence of all subtypes was below that found in most studies of children. While these results imply that ADHD subtypes may be less prevalent in adults, the lower prevalence could also have been due to DSM-IV diagnostic thresholds being too restrictive (i.e., >99th percentile) for use in the diagnosis of adults with ADHD. Further research is recommended to evaluate whether future DSMs should consider establishing thresholds that are developmentally (age) referenced rather than fixed across the lifespan.