A study conducted by the Insurance Institute for Highway Safety (IIHS) and Highway Loss Data Institute (HLDI) has found car crashes increase in states where recreational marijuana is legal.

HLDI writes,

Legalizing recreational marijuana use in Colorado, Oregon and Washington has resulted in collision claim frequencies that are about 3 percent higher overall than would have been expected without legalization . . . .

After comparing collision reports from various states, HLDI concluded collisions claims were 14% higher in Colorado than in neighboring states following the legalization of recreational marijuana in 2012; Washington came in 6% above its neighbors, and Oregon’s collision reports were 4% higher than its neighbors.

IIHS concludes,

“Worry that legalized marijuana is increasing crash rates isn’t misplaced,” says David Zuby, executive vice president and chief research officer of the Insurance Institute for Highway Safety. “HLDI’s findings on the early experience of Colorado, Oregon and Washington should give other states eyeing legalization pause.”

All of this underscores what we continue to say: Marijuana may be many things, but “harmless” simply is not one of them.

You can read more about this study here.