The idea that smoking pot causes can make you crazy is straight out of Reefer Madness. But although we've thankfully gotten away from such a hilariously extreme portrayal, the idea that using marijuana puts you at risk for developing all kinds of mental disorders persists. As usual, the truth is way more complicated than that.

Researchers have tried to figure out whether or not using marijuana leads to mental illness for a long time now. For instance, a 2014 meta analysis looking at results from 31 previous studies found that there is, indeed, an association between cannabis use and anxiety. (That's anxiety disorders, not a short-term state of paranoia that you may find yourself in after a few too many hits.)

So we know that you're (slightly) more likely to have symptoms of depression or anxiety if you're a marijuana user. But whether or not cannabis causes those conditions is a different question — one that still hasn't totally been answered. Some studies say yes (especially for heavy users), others say no.

The truth is that this question is pretty tricky to answer because there's plenty of other evidence suggesting that marijuana can help alleviate symptoms of anxiety and depression. So we're left with a classic chicken/egg scenario: Those who smoke weed and have depression, for example, may not have developed their mental illness as a result of their drug use — instead, they may have taken up drug use as a form of self-medication.

We do know a little more about how using cannabis interacts with other conditions, though. Specifically, there is evidence that marijuana use may cause people who are already at risk of developing their first episode of psychosis (a symptom of schizophrenia) to develop it earlier than they would have otherwise. So, if you're already more likely to have schizophrenia due to a family history, for instance, smoking pot may trigger your first episode about 2.7 years earlier. But, among those who have other risk factors for schizophrenia, cannabis doesn't seem to affect the severity of their symptoms.

And that brings up perhaps the most crucial issue: timing. Just like alcohol and nicotine, marijuana can have an effect on a developing brain if too much is consumed too early. But there's no consensus on what "too much" or "too early" actually means.

So the bottom line is the same as it's always been: Marijuana is a psychoactive drug with potential benefits and potential harms, just like any other drug. But with so much left unknown, it's crucial to put all of this into its larger political context. When marijuana was originally placed into the U.S. government's most restrictive drug classification, we didn't know much about its effects. But now, as we learn more about the possible risks and benefits of cannabis use, we have to use that evidence to shape policy rather than relying on outdated scare tactics.

"Health risks connected with drug use — when scientifically documented — should not be seen as legitimate reasons for criminal prohibition, but instead, as reasons for legal regulation," writes Paul Armentano, deputy director of NORML. Indeed, regulation and harm-reduction are much better, healthier, and more effective approaches to getting people what they need in the safest way possible.