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The Science of Preconceived Notions: Weed as a Gateway Drug

How marijuana became the boogeyman gatekeeper for hard drugs

Most of us go about life with all sorts of preconceived notions. We believe summer colds are worse than winter colds; microwaves cause cancer; and encased meats end up lodged in our colons for years on end, even though none of these things are true. In this series, “The Science of Preconceived Notions,” we’ll attempt to sort through the mix of old wives’ tales, urban legends and general bullshit to find out where the truth really lies.

Marijuana, not even once.

That’s the stance taken by those who believe pot is a gateway drug — that is, that marijuana itself isn’t necessarily dangerous, but undoubtedly leads to harder drug use.

Just last year, the New York Times published an opinion piece arguing the gateway effect associated with marijuana is reason enough to pull back legalization, claiming, “There is ample evidence that early initiation of drug use primes the brain for enhanced later responses to other drugs.” The writer adds that people who are addicted to marijuana are three times more likely to be addicted to heroin.

Admittedly, there are studies — primarily rodent studies — that suggest marijuana use encourages heroin and cocaine addiction. But these studies are tarnished by a fundamental problem (besides the fact that rodent studies don’t accurately mimic human behavior): Most rats hate THC, the active ingredient found in marijuana. This means researchers have to forcibly inject the rodents with a drug that makes them paranoid. For obvious reasons, this causes the rodents a lot of stress, a well-known risk factor for addiction. So rather than proving that marijuana is a gateway drug, these studies simply demonstrate that stressing rats out by getting them high against their will inevitably screws them up.

Still, this idea of marijuana as a gateway drug seems reasonable enough on the surface: Many addicts point to the devil’s lettuce as their introduction to drugs, and there’s a strong correlation between marijuana use and other drug use — studies show that adolescents who use marijuana are 104 times more likely to use cocaine than those who never touched the stuff.

But again, there’s a major flaw with this argument: Correlation isn’t the same thing as causation. Take this example: A professional musician is probably at least 104 times more likely to have listened to music as a kid than someone who’s not a professional musician, but that doesn’t mean listening to music is a “gateway” to becoming a musician. It just means most people listen to music, and those who don’t are even more unlikely to ever become a musician.

Scientists have been promoting this thinking for nearly 20 years now:

Patterns in progression of drug use from adolescence to adulthood are strikingly regular. Because it is the most widely used illicit drug, marijuana is predictably the first illicit drug most people encounter. Not surprisingly, most users of other illicit drugs have used marijuana first. In fact, most drug users begin with alcohol and nicotine before marijuana — usually before they are of legal age.

In the sense that marijuana use typically precedes rather than follows initiation of other illicit drug use, it is indeed a “gateway” drug. But because underage smoking and alcohol use typically precede marijuana use, marijuana is not the most common, and is rarely the first, “gateway” to illicit drug use. There is no conclusive evidence that the drug effects of marijuana are causally linked to the subsequent abuse of other illicit drugs.

The numbers would seem to back this up. The federal government funds two major drug-use surveys every year, and last year, more than 37 million people reported trying pot — compared with just over 5 million who tried cocaine and 948,000 who tried heroin. If marijuana truly were a gateway drug, those numbers would be much more even.

Even more interesting, a five-year-long study published earlier this year argues that cannabis might actually discourage users from progressing to harder drugs, specifically opioids. Of the 125 participants — all of whom used prescription drugs (including opioids) to treat chronic pain — 83 were additionally given medical cannabis. Thirty-four percent of those given medical cannabis to treat their pain stopped using their prescribed painkillers altogether, whereas just two percent of the control group quit taking their initially prescribed drugs. So if these numbers are to be believed, smoking weed actually helped get some people off harder drugs.

This can currently be seen in full effect in Holland. Since the country began liberalizing its marijuana laws, it now has fewer young tokers who move on to harder drugs than most other nations, including the U.S. A 2010 report found that there was “some evidence” for a “weakened gateway” in the Netherlands, and concluded that the data “clearly challenge any claim that the Dutch have strengthened the gateway to hard drug use.”

Which brings us to the question we’ve had all along: If marijuana isn’t a gateway drug, what accounts for the very real correlation between pot use and other drug use? Primarily, the fact that people who are interested in altering their consciousness are bound to do so in a variety of ways. Think about it: Beer lovers don’t just stick to Coors Light, but this doesn’t make Coors Light a gateway to IPAs — it simply means that people who really enjoy beer probably enjoy all kinds of beer, and the same goes for people who really enjoy drugs.

So rather than blaming marijuana for America’s drug problems, we should start looking at what truly puts people at risk. The idea that weed is the first step toward addiction isn’t just blinding us to both its medical usefulness and to the real causes of addiction, it’s also partly to blame for the War on Drugs — and we all know how horribly that went.

Ian Lecklitner is an assistant editor at MEL. He last wrote about how well liquors will give you a worse hangover than top-shelf booze.

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