Marijuana Impacts Your Driving: New Study Reveals Pot's Influence

How does marijuana impact your driving? That's a good question and now, researchers have taken a closer look. A new study has found drivers who use alcohol and marijuana together weave more on a virtual roadway than drivers who use either substance independently.

"What we saw was an additive effect, not a synergistic effect, when we put them together," said Tim Brown, corresponding author of the study, in a news release. "You get what you expect if you take alcohol and cannabis and merge them together."

The results were actually part of a larger study, which was the first of its kind to analyze the effects of inhaled cannabis on driving performance. It found that participants who consumed only alcohol weaved more during the simulated driving test than those who consumed only vaporized cannabis.

To date, medical marijuana is legal in 23 states and the District of Columbia. Marijuana has also been approved for recreational use in four states and D.C. Since legalizing medical marijuana, though, Colorado has reported an increase in driving under the influence of cannabis cases and fatal motor vehicle crashes with cannabis-only positive drivers. States without legalized marijuana have experienced no significant change in cannabis-related crashes.

"Alcohol is the most common drug present in the system in roadside stops by police; cannabis is the next most common, and cannabis is often paired with alcohol below the legal limits," said Brown. "So the questions are: is alcohol an issue? Is cannabis an issue? We know alcohol is an issue, but is cannabis an issue or is cannabis an issue when paired with alcohol? We tried to find out.

In the end, the researchers found that drivers with blood concentrations of 13.1 ug/L THC, the active compound in marijuana, showed increase weaving that was similar to those with .08 breath alcohol concentration, the legal limit in most states.

The findings reveal a bit more about what limits should be set for cannabis when it comes to driving. This is especially important as marijuana is legalized in more and more states.

The findings are published in the journal Drug and Alcohol Dependence.

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