Abstract
Individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) are at disproportionate risk of collision when driving. Recently efforts have been made to determine whether stimulant medications improve driving in individuals with ADHD. This study was designed to measure the effects of long-acting Multi-Layer Release (MLR) Methylphenidate using a double-blind placebo-control crossover design. A fixed-base driving simulator was used to measure driving performance (a full car body surrounded by viewing screens providing a 300[sup]o[/sup] wrap- around virtual reality). Drivers with a history of ADHD and meeting the DSM-IV criteria for ADHD were recruited. Methylphenidate dosage was optimized and stabilized before testing began (M dosage = 47.7 mg). Thirty drivers between the ages of 21 and 65 years were tested in the simulator on two weekends, one week with their usual dose of MLR Methylphenidate and the other with a placebo. (Half the drivers began with the medication; the other half began with the placebo.) Each test day drivers were tested 1hour before the treatment/ placebo and then 2, 9, 12, 14 and 16 hours post-administration. Driving performance was measured in terms of collisions, hazard response time, steering variability, and driving speed. The age range of drivers in this study was larger than in previous ADHD studies and age appears to have an influence on the effect of the treatment on driving. Post-hoc analyses revealed that although the medication significantly improved performance in drivers under the age of 45, as shown in hazard response times and time spent speeding, there was no corresponding improvement in drivers over the age of 45. This may mean that older drivers with ADHD learn strategies to compensate for their deficits and consequently no medication-effects were observed. Alternatively, this may mean that there are age differences in the effects of medications such as MLR Methylphenidate on driving performance.
Meeting abstract presented at VSS 2013