Cannabis and its effect on motor vehicle accidents

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. I realize that not all the information and research is complete on the use of the drug, especially in its multiple forms.

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.

DR. ROACH WRITES: Flu season is coming again, and once again there are a myriad of flu shots available. Most people can get any of the vaccines, but I would recommend a quadrivalent, which protects against four strains, over the trivalent, which protects against only three. Adults over 65 should get the high-dose vaccine (Fluzone high-dose) or adjuvant vaccine (Fluad) if available. People with severe egg allergies can get a cell-culture vaccine (Flucelvax) or recombinant vaccine (Flublok). This year, the Centers for Disease Control and Prevention has endorsed the live, attenuated nasal vaccine (FluMist), which is indicated only for ages 2-49, and should not be given to people with compromised immune systems or who will be around people with severely compromised immune systems. People with such immune system disease and their caregivers are particularly encouraged to get one of the available vaccines by injection.

Influenza is already being reported, so it might be a good idea this year to get the flu vaccine sooner, rather than later. It seems like this year may be an early year for the flu, which is a serious disease that kills many thousands of people yearly in North America.