There’s very little debate that marijuana is reasonably safe for adults. There is very little debate that pregnant women should not do drugs or drink alcohol—even though most drugs are not as harmful as people think there is no question that they are drugs and that they do affect the fetus. What’s a little fuzzier is determining when someone can safely smoke marijuana: Fourteen? Eighteen? Twenty-one?
It turns out that smoking marijuana as a teenager could increase your odds of developing immune system disorders as an adult. Researchers in Italy found that mice exposed to THC at 33 days old (the equivalent of a human 12-18 year-old) for ten days initially produced less pro-inflammatory cytokines compared to placebo-treated animals, but 47 days after treatment, their pro-inflammatory cytokine levels rose to levels higher than those of placebo-treated animals—and much higher than age-related controls. Analysis of the cytokine profile indicates that exposure to marijuana tends to skew the T-cell (the immune cells that kill infected cells, or help kill infected cells) profile away from cell-mediated immunity and more towards a pro-inflammatory response. And this isn’t just true of adolescent mice, either. Mice exposed to THC as adults also displayed a similar, albeit less dramatic alteration in their cytokine profiles.
And that’s not all. Macrophage (white blood cells that literally eat foreign particles) function was significantly reduced immediately after exposure to THC and increased after 47 days. Furthermore, THC also seemed to affect the kind of antibodies produced.
The usual caveats apply, here: this is a study done in mice, and mice are not humans; they injected THC under the skin rather than allowing the mice to inhale the vapors. But we know enough about how marijuana affects the immune system and how these changes can be permanent that it would be unwise to dismiss this study as merely an academic exercise.
The other thing to keep in mind, though, is that these mice had no choices: they were fed standard mouse chow, housed in standard cages with standard toys. They could not decide to take control of their lives, eat a better diet, or exercise more. And that’s the thing with medical marijuana: if it makes it easier for you to live a better life, then that could very well counteract the pro-inflammatory effects. The study does make a valid point—we don’t know exactly what goes on in the long run when it comes to drug exposure, and more people can get their hands on it than ever. Marijuana is not dangerous enough to become a public health hazard, of course—but it would be a disservice not to be aware of any risks it can pose.