Americans have favorable beliefs about medical marijuana that aren’t yet supported by the scientific research, according to a new study from the Annuals of Internal Medicine.

Medical marijuana, and cannabis more broadly, is growing in popularity and approval. Business is booming (especially in California) and the US Food and Drug Administration just approved the first cannabis-derived drug. For the study, the authors surveyed about 16,000 Americans about their attitudes toward marijuana. Their results showed that 81 percent of the respondents believed that marijuana had at least one medical benefit, in areas such as pain management, treating diseases, and alleviating mental health problems.

But, as the authors note, we don’t actually have high-quality clinical evidence that marijuana does do all these things. The research is promising, but not rock solid. As neurologist Steven Novella notes at Science-Based Medicine, most published studies are poorly designed. (As of 2013, fewer than 20 randomized controlled trials — the gold standard for scientific research — have tested the benefits of marijuana, according to the American Medical Association.) Some don’t necessarily show marijuana doing better than placebo, and many don’t investigate whether marijuana actually reduces symptoms or if it just makes people care less. There’s a lot we don’t know.

All this is because the Drug Enforcement Administration makes it extremely difficult to research marijuana. As just one example, scientists who want to study the substance must use federally approved examples. Two years ago, the agency said it’d give licenses to more universities to do marijuana research with the goal of helping with the studies. But Stat reported this week that the DEA has not granted these additional licenses and has stopped accepting new ones.

These are the kinds of policies that make it hard for us to see through claims flying in all directions. A few decades ago, we had Reefer Madness and propaganda about the overblown dangers of marijuana. Today, some have swung in the other direction, setting their sights on marijuana as a wonder drug with few downsides, even as rates of marijuana addiction are growing. The only way to have a clear-eyed view of both the benefits and harms of marijuana is by making it easier to study; by extension, that’s the only way for us to cut through the hype and make the most informed decisions.