*The following is excerpted from an online article posted on SciTechDaily.
A study by McLean Hospital’s Mary Kathryn Dahlgren, Ph.D., Staci Gruber, Ph.D., and their team from McLean’s Cognitive and Clinical Neuroimaging Core and the Marijuana Investigations for Neuroscientific Discovery (MIND) program, has found that recreational cannabis use affects driving ability even when users are not intoxicated by marijuana.
Published in the Drug and Alcohol Dependence journal, the study “Recreational Cannabis Use Impairs Driving Performance in the Absence of Acute Intoxication,” finds that in addition to chronic, heavy, recreational cannabis use being associated with poorer driving performance in non-intoxicated individuals compared to non-users, the researchers linked earlier onset of marijuana use (under age 16) to worse performance.
Researchers used a customized driving simulator to assess the potential impact of cannabis use on driving performance. At the time of the study, marijuana users had not used for at least 12 hours and were not intoxicated.
Overall, heavy marijuana users demonstrated poorer driving performance as compared to non-users. For example, in the simulated driving exercise, marijuana users hit more pedestrians, exceeded the speed limit more often, made fewer stops at red lights, and made more centerline crossings.
When researchers divided marijuana users into groups based on when they started using cannabis, they found that significant driving impairment was detected and completely localized to those who began using marijuana regularly before age 16.
“It didn’t surprise us that performance differences on the driving simulator were primarily seen in the early onset group,” Dahlgren said. “Research has consistently shown that early substance use, including the use of cannabis, is associated with poorer cognitive performance.”