 Why is there such a dearth of rigorous research on the effects of marijuana? The first major study wasn't published until 2007. Why did it take so long? Why did the pharmaceutical industry fail to show any interest? Some might prefer a simple answer, since it's just a plant. It can't be patented for your stockholders, thus removing any incentive for investing corporate funds. Yes, but it's more complicated than just that. There are research funds available— $100 million of public money in a single year. But historically, that money was generally obtainable only for research on the negative effects. See, in the US, cannabis is still officially lumped in with heroin as a Schedule 1 drug, which means by definition, it's classified by the government to have no medicinal value. A designation that resulted in a near cessation of scientific research, particularly since the only way researchers could get it without risking jail time, is a state-run farm in Mississippi, controlled by the National Institute on Drug Abuse, which has historically only green-lighted research aimed at demonstrating harmful effects. Residents of 23 states can walk out and just buy it, but US scientists must wade through onerous paperwork, and even when they do get it, it's the wrong stuff. It's not what people are actually using these days. The studies coming out are unlike your grandma's grass, a few percent THC, where the stuff available these days may be 10 times more potent. So there's like this crazy catch-22, where the cannabis that should be studied is illegal, and the cannabis that can be legally studied, the decades-old Mississippi strain, is essentially kept off-limits. So ill-informed practitioners are thus left to do with like anecdotes off the internet like everybody else, which is bad medicine. As long as clinical research on cannabis is controlled by regulators expressly opposed to the stuff, we may miss out on potential benefits. That's no excuse, though. Just because there are political barriers to research doesn't mean we should lower our bar in terms of demanding evidence. The sick still need medically sound treatments. Of course, now there's pressure coming from both sides. The marijuana industry is now big business, and with those billions can rally the troops. Cannabis researchers already talk of being bombarded with emails from pro-canabis groups if they dare make any negative comments about the drug. A lot of research is like tobacco research in the 60s, as one University of Colorado researcher, and so now there's fear big money will push the pendulum too far the other way. But the barriers go beyond money, politics, and prejudice. Cannabis research is hard to do. I mean, how do you do a double-blind study with marijuana? People know when they've been duped with placebo dope. People can tell the difference between pot brownies and regular brownies, otherwise they wouldn't eat them. And so if you know you're getting the active drug, the placebo effect can kick in hard, notes one neurobiology researcher, especially when you're dealing with subjective outcomes like pain or mood. And imagine if you're trying to do a population study on memory or cognitive impairment, and you're asking heavy pot smokers to try to remember how much they've been smoking over their life, I mean you can imagine how that might influence data accuracy. Let me give you an example of how convoluted this can get. Neuropsychological testing of cannabis users have found residual negative effects in terms of scoring slightly lower on memory tests. But how do we know it's not a matter of motivation rather than actual cognitive impairment? That had never been tested until this study. They gave a group of potheds a standard learning test and just gave the standard spiel, you know. Please complete the following series of tasks which measure different areas of cognition, like memory and attention. That's what you'd normally say. And when you do, pot smokers score significantly worse. Ah, but what if you instead said this? Please complete the following series of tasks. It's important that you try your very best on these tasks because this research will be used to support legislation on marijuana policy. So hey, if you do good, they might decriminalize weed or something. And under those circumstances, boom, the apparent cognitive impairment disappears. Now you could argue that lack of motivation is a problem in and of itself, but hey, it's better than having long-term brain damage.