Effects of two doses of methylphenidate on simulator driving performance in adults with attention deficit hyperactivity disorder

Introduction: Numerous studies have documented an increased frequency of vehicular crashes, traffic citations, driving performance deficits, and driving-related cognitive impairments in teens and adults with attention deficit hyperactivity disorder. Method: The present study evaluated the effects of two single, acute doses of methylphenidate (10 and 20 mg) and a placebo on the driving performance of 53 adults with ADHD (mean age=37 years, range= 18-65) using a virtual reality driving simulator, examiner and self-ratings of simulator performance, and a continuous performance test (CPT) to evaluate attention and inhibition. A double-blind, drug-placebo, within-subjects crossover design was used in which all participants were tested at baseline and then experienced all three drug conditions. Results: A significant beneficial effect for the high dose of medication was observed on impulsiveness on CPT, variability of steering in the standard driving course, and driving speed during the obstacle course. A beneficial effect of the low dose of medication also was evident on turn signal use during the standard driving course. An apparent practice effect was noted on some of the simulator measures between the baseline and subsequent testing sessions that may have interacted with and thereby obscured drug effects on those measures. Conclusions: The results, when placed in the context of prior studies of stimulants on driving performance, continue to recommend their clinical use as one means of reducing the driving risks in ADHD teens and adults. Impact on industry: Given the significantly higher risk of adverse driving outcomes associated with ADHD, industry needs to better screen for ADHD among employees who drive as part of employment so as to improve safety and reduce costs. Use of stimulants to treat the adult ADHD driver may reduce safety risks. (c) 2005 National Safety Council and Elsevier Ltd. All rights reserved.