Q: Is marijuana addictive?
—John Stone ’05
A: Often people will say things like: “Marijuana isn’t physically addictive, is it? It’s only psychological.” It is true that the tremors, nausea, and seizures that might accompany withdrawal from various other drugs are not present with marijuana. But there can be significant psychological dependence: cravings, inability to control use, difficulty ceasing use, and continued use despite adverse consequences (say, performance problems in school or work). These so-called “psychological” phenomena are actually the key symptoms of addiction and are related to physical things happening in the brain, they are just not so readily visible.
Because of its illegality, few studies have been done to quantify the prevalence of marijuana addiction, despite the fact that marijuana is the most widely used illegal psychoactive substance. My guess is that the addiction risk of marijuana is comparable to that for alcohol, that is, most people who use it do not get into an addictive relationship with it, but a significant percentage do. For alcohol it may be about 15 percent of users. For marijuana, who knows?
—Thanks to David Presit, senior lecturer of neurobiology