What happens when you mix cannabis and alcohol?

Have you ever heard of polyconsumption? It may sound like a complex medical term, but the Centers for Disease Control and Prevention has a pretty simple definition: Polyconsumption is “the use of more than one drug, also known as polysubstance use. This includes when two or more intoxicating substances are taken together, either intentionally or unintentionally.” Essentially, every time you drink a beer and smoke a joint, you are poly-consuming.

With polysubstance use on the rise, we want to ensure everyone is aware of the physiological and behavioral impacts of combining the two drugs. Using cannabis and alcohol together enhances the effects of each, causing increased impairment, such as:

• Slowed reaction time.
• Loss of coordination and problem-solving skills.
• Distorted perception of time, distance and speed.

So, why does it matter? Why do CDOT and law enforcement agencies believe this is an issue we need to address? While the use of cannabis is legal in Colorado, driving while intoxicated is not. According to the CDOT Data Intelligence Group, poly-impaired drivers were involved in 32% of fatal crashes in 2024.

The Colorado Division of Criminal Justice (DCJ) published a report in July 2023 that analyzed 2020 data from more than 21,000 impaired driving cases filed in Colorado. Researchers followed the cases from arrest to final court outcome. The DCJ report found:

• Eighteen percent of impaired drivers arrested tested positive for multiple substances. The most common combination was alcohol and Delta 9-THC, which is the primary psychoactive component of cannabis.
• The second most common pairing was alcohol combined with other drugs such as cocaine, methamphetamine, sedatives and opioids.
• Seventy-five percent of individuals with detected Delta-9 THC also had some other substance present. Alcohol was the most common co-occurring substance.

This is not just a Colorado issue. According to the Insurance Institute for Highway Safety, “A third of drivers (nationwide) who drink alcohol and use marijuana at the same time report getting behind the wheel within two hours of consumption.”

Research also shows that users are more likely to drive — or take other risks — after using both substances than after consuming marijuana alone.

Impairment-related fatalities are on the rise in Colorado. About one-third of traffic deaths involve an impaired driver. It’s our mission to educate and inform Coloradans to make the right decision to never drive high, but the bottom line is it’s up to you. With everything on the line from a DUI to a life lost, what decision will you make?

Poly-Impaired Driving

Driving under the influence of alcohol, cannabis, natural medicine (psilocybin) or other drugs — especially when combined — is dangerous and illegal. Using two or more intoxicating substances together (also known as “poly-consuming”, “polysubstance use” or “polydrug consumption”) enhances the effects of each substance and increases the risk of a crash. In fact, about one-third of drivers in fatal crashes involving impairment in Colorado test positive for multiple impairing substances, including alcohol. Motorists should know that Colorado Drug Recognition Experts (DREs) are trained to recognize impairment in drivers under the influence of drugs and/or alcohol, and that impaired driving of any kind can lead to a DUI arrest.