Cannabis data appear contradictory

Dear Dr. Roach: In a recent column, you mentioned that “Cannabis adversely affects driving ability.” Yet, further on in the article, you state that, “Early data from areas that legalized recreational marijuana suggest reduced rates of motor vehicle accidents.”

These two statements seem to contradict each other. I believe I’ve read several articles that state the vehicular accident rate in Colorado has risen since the legalization of marijuana there. I think it would be beneficial to know which is more indicative of the true effects of marijuana on a person’s driving ability.

Full disclosure: I am against legalizing the drug but have no problem with its controlled use for medicinal purposes. However, you know as well as I do that many health prescribers and users abuse the drug for medicinal purposes. I’m simply against the use of ANY drug that can impair a person’s ability to drive!

Anon.

Answer: I see the apparent contradiction, and hope I can explain it.

The answer is that while, as you say, it’s certainly best not to drive on any substance, it appears that states with legalized cannabis use have less unsafe alcohol use. The collision data is more complex than I had space to discuss. While collisions have increased by about 3 percent, fatalities have gone down by about 10 percent. These results are particularly strong in younger age groups.

I certainly agree that use of any performance-affecting drug before driving is a very bad idea. However, alcohol appears to be much more dangerous, so the net effect is less mortality with respect to traffic accidents.

Finally, any drug, prescription, over-the-counter or recreational, can be abused. I think the data are clear that cannabis has legitimate medical uses, and that recreational use of cannabis may reduce overall morbidity and mortality, if users are using less alcohol, which is responsible for far more deaths than cannabis is.

There is a great deal of uncontrolled cannabis use, both recreationally and to treat symptoms. More control and more data both are good ideas.

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