Cannabis and alcohol are two of the substances most commonly used together, yet many people use them without understanding how these two substances interact or how their combined use can affect driving ability.

A recent study took a closer look at what happens when people consume cannabis edibles and alcohol together and assessed the impact on driving performance. The study found that combining cannabis and alcohol lead to greater and longer lasting impairment than using either substance alone. Even low doses of both substances significantly reduced driving performance.

In many countries, the legal blood alcohol concentration (BAC) limit for driving is o.o5%, based on evidence showing that impairment begins well before the 0.08% limit used in the United States. The findings from this study suggest that when alcohol is combined with cannabis, impairment may occur at levels below current legal thresholds, raising important questions about what constitutes safe driving.  

Another key issue highlighted in this study is the potential lack of efficacy relating to tools used to detect impaired driving. Although participants showed driving impairment in a simulator, standard sobriety tests did not detect impairment. It’s important to note that these tests were originally designed to detect alcohol impairment, not cannabis. As a result, individuals may appear to “pass” a sobriety test while still experiencing significant impairment.

With cannabis use increasing, especially in states where it is legal, these findings raise important questions about whether current impaired-driving laws and detection methods are keeping up with current behavior. In Canada, where cannabis is legalized, stricter rules have been considered for drivers who combine alcohol and cannabis. Continued research, policy evaluation, and public education are critical to helping communities better understand the dangers of combining cannabis and alcohol and to reducing impaired driving on our roadways.

References:

  • Dave, R. (2026). Co-use of cannabis edibles and alcohol increases driving impairment, suggests JAMA study. Medical Dialogues. https://medicaldialogues.in/amp/psychiatry/news/co-use-of-cannabis-edibles-and-alcohol-increases-driving-impairment-suggests-jama-study-172288
  • Zamarripa, C. A., Lin, S., Klausner, M., Rastogi, K., Roche, D. J. O., Novak, M., Antoine, D., Wolinsky, D., Marcotte, T. D., Weerts, E. M., Vandrey, R., & Spindle, T. R. (2026). Impact of cannabis edibles combined with alcohol on driving, field sobriety performance, and subjective effects: A within-participant crossover trial. JAMA Network Open. doi:10.1001/jamanetworkopen.2026.9842