This week, a team from the National Institute on Drug Abuse (NIDA) reported that heavy marijuana use may damage the brain’s pleasure center. Meanwhile, researchers in the United Kingdom say they’ve figured out why pot makes you paranoid. But does focusing research on cannabis’s “bad side” give the drug short shrift? Science talked to Ian Mitchell, an emergency physician at the University of British Columbia’s Southern Medical Program in Kamloops, Canada, and author of the blog Clinical Cannabis in Context, who says that politics influences research in this controversial field. As a doctor who recommends medical cannabis to patients, he follows research on the drug and often critiques studies he believes are based on outdated information or were performed with an anticannabis bias.This interview has been edited for clarity and brevity.Q: What do you think of the NIDA study? 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One of the ways you could interpret that is, OK, these pleasure centers are damaged. But you could also say, perhaps marijuana decreases the effects of [Ritalin] on people. That would be equally as right an interpretation.Q: Why do we hear more about studies that show negative effects of marijuana?A: NIDA is at the center of cannabis research in America. And their mandate, very plainly, is to study drug abuse. So they overwhelmingly fund studies that look at abuse. In America, if you wanted to run a study that showed a benefit of cannabis, you weren’t allowed to do that because NIDA couldn’t give you samples to use. So there were no trials [on potential medical benefits] being done. For example, there hasn’t been a good trial yet to study marijuana’s potential for treating posttraumatic stress disorder. They couldn’t get it done, due to all these political roadblocks.Q: How are changing laws—for example, legalization in Colorado, Washington, and Uruguay—influencing research on marijuana?A: Research on marijuana is flowering. States like Colorado are earmarking portions of revenue generated from marijuana sales for research. That’s going to be very helpful, because that money [unlike NIDA funding] will be free to be applied to looking for benefits. There’s certainly a lot more interest in it, and the political situation I think has improved significantly.I think it’s also very important to track social data about recreational use. Now, in Washington and Colorado, they’re tracking data on traffic accidents and fatalities, pedestrian accidents, suicide rates, homicide rates, that type of thing. That’s a tremendously important amount of data that has not really been tracked so far. Now that recreational use in those areas is legal, it’s much easier to study. In areas where it’s illegal, you can’t really ask people about those kinds of behaviors because they don’t want to get arrested.Q: Is there a danger that research on the medical benefits of marijuana will be politicized, too? Sometimes you’ll hear about anecdotal evidence of marijuana shrinking tumors, for example.A: Absolutely, and I think that’s a big concern. But that’s why the research needs to get done, because we have all these little stories of people saying, “I used this and my cancer got better.” And that’s nowhere near enough good evidence to start changing practice.There’s a lot of criticism leveled at cannabis research overall, and I expect it to continue. So the studies have to be good. They have to be of excellent quality, and they have to be scrutinized. And I’m sure they will be, very closely.