Article by Sara Diedrich, Iowa Now
A new study conducted at the University of Iowa’s National Advanced Driving Simulator (NADS) has found drivers who use alcohol and marijuana together weave more on a virtual roadway than drivers who use either substance independently. However, the cocktail of alcohol and marijuana does not double the effect of the impairment.
“What we saw was an additive effect, not a synergistic effect, when we put them together,” says Tim Brown, associate research scientist at NADS and co-author of the study. “You get what you expect if you take alcohol and cannabis and merge them together.”
The study, which was published June 23 in Drug and Alcohol Dependence, also found that participants who consumed only alcohol weaved more during a 35- to 45-minute simulated driving test than those who consumed only vaporized cannabis. Gary Gaffney, associate professor of psychiatry in the UI Carver College of Medicine, is the study’s principal investigator. It’s co-principal investigators are Brown and Gary Milavetz, associate professor and head of the division of Applied Clinical Sciences in the College of Pharmacy.
The results are part of a larger study—the first of its kind to analyze the effects of inhaled cannabis on driving performance—sponsored by the National Highway Traffic Safety Administration, National Institute of Drug Abuse, and the Office of National Drug Control Policy. The UI was selected for the research because of the NADS’ authenticity to real driving and the university’s expertise in medicine, pharmacy, and engineering. The NADS is the only simulator of its kind that is publicly owned.
The outcomes could help shape future legislation in the United States where some experts say policies on drugged driving are woefully behind.
To date, medical marijuana is legal in 23 states and the District of Columbia while marijuana has been approved for recreational use in four states and D.C. Since legalizing medical marijuana, Colorado has reported an increase in driving under the influence of cannabis cases and fatal motor vehicle crashes with cannabis-only positive drivers while states without legalized marijuana have experienced no significant change in cannabis-related crashes.