A Johns Hopkins Medicine study supported by the National Institute on Drug Abuse found that cannabis edibles and alcohol together produced stronger driving impairment than either substance alone. The research, published in JAMA Network Open, strengthens evidence that combining cannabis edibles with alcohol can make driving impairment worse than using either substance by itself, while standard field sobriety tests failed to detect cannabis-related impairment.
Study Design and Findings
Thirty healthy adults ages 21 to 55 participated in carefully controlled experimental sessions where they received either a cannabis-infused brownie (10 or 25mg THC) or a placebo brownie, followed by either an alcoholic beverage producing breath alcohol levels of 0.05 percent or 0.08 percent, or a non-alcoholic placebo drink. The findings showed that mixing cannabis edibles with alcohol caused greater and longer-lasting driving impairment and stronger feelings of intoxication than either substance alone. Standard field sobriety tests, however, classified participants as intoxicated only in the high alcohol dose condition (0.08 percent BrAC) compared with placebo, indicating that cannabis-related impairment was missed by roadside detection methods.
Implications for Safety and Policy
The study’s lead author, Austin Zamarripa, Ph.D., notes that “co-use of cannabis and alcohol produces significantly greater driving impairment” and that “the interaction between cannabis edibles and alcohol is not merely additive, but may be synergistic in producing impairment, which has important implications for real-world risk.” The findings suggest that the legal alcohol intoxication limit used across most of the U.S. (0.08 percent BrAC) may be too high for drivers who have consumed both cannabis and alcohol. Researchers emphasize the need for broader public awareness about stronger effects from combined use and note that roadside methods for detecting driver impairment need improvement.
This article is an AI-assisted summary. All facts and figures are drawn from the original report: https://scitechdaily.com/mixing-edible-cannabis-and-alcohol-may-impair-driving-more-than-scientists-expected/