How Risky Is it to Smoke Pot? One Expert's Take
Marijuana has long had the reputation of being a relatively harmless drug. Two recent studies, however, highlight its potential dangers: One suggests that using marijuana increases the odds of eventually developing a psychotic disorder, while the other found that smoking one marijuana joint affected the lungs as much as smoking five cigarettes. We spoke with Marc Kaufman, director of the Translational Imaging Laboratory at McLean Hospital, a Harvard-affiliated psychiatric hospital, and an associate professor of psychiatry at Harvard, to get some perspective on pot. He studies the effects of drugs on the brain and other bodily systems.
Is it biologically plausible that marijuana could mess with your head?
Sure. There are receptors for cannabinoids [the active compound in marijuana] in the brain that send signals and modify other systems, such as the dopamine and glutamate systems. Changing the neurochemistry of the brain may alter those systems–it's very hard to predict. They all interact with each other.
The study on psychosis showed that smoking marijuana raised the risk–which is quite low–by 40 percent. Does this mean that smoking marijuana causes schizophrenia or other psychotic disorders?
No. It shows that people are more likely to get those symptoms if they use marijuana, but it might be that the marijuana is unmasking something that's already there. It's very hard to say there's a definitive cause and effect.
You say the study about lung function has much broader implications for public health.
If marijuana can unmask a predisposition for psychosis, only a small number of people might experience this unmasking. But the lung findings are very interesting, apart from what they mean for lung health [the study found that smoking cannabis is associated with impeded airflow]. Other research has shown that in people who aren't necessarily drug abusers, poor lung function is related to poor cognitive function. That would affect more people.
What about the medical benefits of marijuana?
There's clearly a debate in society about whether people should be able to use these drugs [in a medical setting] to counteract the nausea associated with cancer treatment. But what we can tell from the lung study is that while there may be some beneficial effects, marijuana may have some downstream effects on the brain. What many researchers are trying to do is to come up with drugs that are selective–they'll bring the same benefit, such as combating nausea, but won't produce a high or damage the lungs.
I was always taught that marijuana wasn't physically addictive. True?
There's been a controversy over the years, but we're seeing that there really is a withdrawal or a dependence syndrome. People who have smoked a lot of marijuana tend to experience increased cravings, sleep problems, increased aggressiveness, and restlessness when they try to quit. The symptoms can last 10 days, so it can be really hard to quit. People are beginning to accept that there's this dependence system, and there's an appreciation that we have to consider marijuana abuse treatment. We need to come up with some medications that can treat dependence.
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