You may have read last week that new research from an impaired driving cannabis study that found cannabis use affects driving even after effects have worn off—and that heavy use impairs driving. We have had to report critically on this kind of research and reporting before.
These headlines are simply misleading, based on what we actually found in the press releases. Here’s what they found.
No, cannabis does not impair drivers even the next day
People who started using cannabis daily before age 16 engaged in more “impaired driving” than sober controls, even when they were not high. By “impaired driving,” the researchers found they drove at higher speeds, had more accidents, and drove through more red lights than people who did not start using cannabis every day before turning 16 years old.
They specifically point out two other things. First, adjusting for age completely produces the effect. In other words, it is NOT cannabis users as a group. It is just this group of people who become lifelong, daily users before they are 16.
Second, these findings may reflect the fact that people who follow that pattern and initiate substance use during adolescence may also be showing the kind of increased impulsivity that would cause speeding and other kinds of reckless driving.
Takeaways from the impaired driving cannabis study
The point is, that these headlines about “Impaired driving—even once the high wears off” and “Even when sober, frequent marijuana users are dangerous drivers, report finds” are inaccurate and misleading.
The authors also suggest that their results mean early exposure to cannabis can cause later difficulties performing complex cognitive tasks. This is a theory for later research, but hardly a clearly proven result from this work.
They are right to suggest that impulsive behavior is going to be a critical factor in this group. (And, as an aside, these kinds of people as adults may be self-medicating with cannabis for ADHD and similar problems.)
Finally, some reporting continues to repeat the tired claim that traffic incidents explode in recreational cannabis and medical marijuana states. However, this is not the case. All available research seems to show that traffic incidents stay about the same over time—although the landscape is changing so quickly, it’s hard to tell.
The bottom line is that the findings do not appear to suggest that all cannabis users exhibit impaired driving when sober. Not even close, no matter what the headlines suggest.