“Is marijuana really better for our health than cigarettes are?”

—Kristina M.*, Western Illinois University (*name changed)

To be clear: We’re comparing two unhealthy behaviors. People are more likely to maintain their health if they don’t smoke anything at all.

But if we’re talking about what’s “better,” we need to know exactly what we’re comparing. People consume marijuana in many different ways, and the source of marijuana matters. For example, as marijuana becomes legalized in more states, the concern about “adulterants,” other substances or chemicals that may be added to increase volume when sold on the black market, probably goes down.

To answer your question, we’ll compare the most similar products: a hand-rolled tobacco cigarette and a hand-rolled marijuana cigarette (joint).

The harm from one inhalation or toke is probably about equal.

Both are inhaled. This means that multiple harmful chemicals (both from the rolling paper and the leaf/bud) are taken into the lungs. The difference is that people tend to consume significantly more inhalations of tobacco than marijuana, so they likely inhale more times from a tobacco cigarette and they likely smoke more tobacco cigarettes in a day. Effectively, that can add up to more harm from tobacco cigarettes.

A filtered cigarette provides some protection compared to an unfiltered hand-rolled smoke, but it’s not exactly healthy.

So what about using some type of filter—for example, smoking from a bowl or bong, or using a vaporizer? Here it gets complicated very quickly. We can make fairly reliable comparisons between different commercial cigarettes (how does this brand stack up against that one?), but it’s very difficult to compare one bag of weed to another, much less compare a bag of weed to a THC-containing liquid smoked with a vaporizer.

Fundamentally, inhaling anything other than fresh country air is potentially harmful.

It is reasonable to assume there is a dose-dependent relationship. In other words, the more harmful substances you inhale, the worse for you. Of course, less of a more-harmful substance may do more damage than more of a less-harmful substance. For example, one inhalation of a marijuana cigarette adulterated with chemicals would likely be more harmful than several inhalations of a similar marijuana cigarette without chemicals.

Both tobacco and marijuana can trigger the reward center in susceptible brains and lead people to continue to use, despite the health, social, financial, or other complications.

Also, we can’t ignore the risks of any kind of exposure to either nicotine or marijuana.

In the end, I can’t really tell you which is better, because I’m not certain what we’re comparing. The less you consume (as measured, I would suggest, by inhalations), the better. The long-term adverse health effects of tobacco are well documented: heart disease, cancer, etc. To date, marijuana is less studied. This is expected to change as legalization advances.

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The doc

Dr. Davis Smith is an internist practicing in Connecticut and at Trinity College in Hartford. He specializes in the care of adolescents and GLBTQ patients.