Why Has Drunk Driving Decreased in States With Legal Medical Marijuana Programs

Written by Lydia Kariuki

One of the side effects associated with marijuana use is that it causes “impaired reaction time in critical situations”. This means that someone behind the wheel may not be able to respond to a road emergency on time.  This should result in increased road accidents in states where marijuana has been legalized, right?

A new study has revealed an interesting correlation between cannabis use, drunk driving (driving under the influence of alcohol) and road accidents. In states where marijuana (medical) has been legalized there seemed to be a drop in alcohol-related road accidents.

A professor at the University of Iowa’s College of Business, Cameron Ellis, reviewed data on vehicle crashes that occurred between 2014 and 2019 by ZIP code. He compared this information against car insurance rates in the same zip codes over the same period of time.

Ellis made the following observations:

  • States with a legal medical marijuana program witnessed a drop of $22 per driver on average in yearly insurance premiums

  • States that had the highest incidences of drunk driving prior to legalization and zip codes that were located close to cannabis dispensaries had higher drops in insurance premiums

The findings clearly depict a relationship between medical marijuana use and reduced car insurance premiums, which of course suggests a reduced incidence of drunk driving-related accidents.

However, Ellis arrived at the following conclusions:

Where medical marijuana was legalized, people switched from alcohol to cannabis.


According to Ellis, alcohol emboldens users and makes them more willing to get behind the wheel even when intoxicated. Conversely, cannabis makes users paranoid and afraid to get behind the wheel.

Hence, when people switch from alcohol to cannabis there’s likely to be a reduction in road accidents resulting from DUI.

About the author

Lydia Kariuki