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Once and for All, Marijuana Is Not a Gateway Drug

According to many studies, weed seems more like a filter that keep people away from stronger drugs than a stepping stone into life-destroying addiction.
Photo via Flickr user Blind Nomad

As the 2016 election approaches, marijuana legalization is in the air once again, with ballot initiatives likely to succeed in at least five states, including California. As usual, politicians—including some presidential candidates, notably Carly Fiorina—are trying to turn back the tide by spreading fear that weed is a gateway to more dangerous drugs. But research increasingly shows not only that the "gateway" theory is incorrect, but that weed may actually help people with addictions stop taking other drugs, rather than start.


On the surface, the gateway idea seems reasonable enough. After all, there are almost no heroin users who didn't start their illegal drug use with marijuana, and marijuana smokers are 104 times more likely to use cocaine than those haven't tried weed.

Yet as scientists constantly remind us, correlation isn't the same thing as causation. For example, the number of people killed annually by dogs correlates almost perfectly with the growth in online revenue on Black Friday. And the rise in autism diagnoses is strongly correlated with the growth in sales of organic food. It's technically possible that some third factor causes both of these apparently haphazard connections. However, it's completely implausible that these connections are causal, and odds are that the links are due to random chance.

In terms of marijuana's specific correlation with other drug use, slightly less than half of Americans over 12 have tried marijuana, while less than 15 percent have taken cocaine and less than 2 percent used heroin, according to the latest National Household Survey on Drug Use and Health. Even smaller portions go on to become addicted to those drugs: Typically, only 10 to 20 percent of those who try alcohol and other drugs get hooked.

If marijuana were causing other drug use, most users should progress to more dangerous substances. But they don't. By the numbers, marijuana use seems more like a filter that keeps most people out than a gateway that lets the majority pass through.


While there are a few rat studies that suggest marijuana use "primes" exposed rodents to take more heroin or cocaine when it is offered, they are marred by a fundamental problem. Most rats do not like THC, the main active ingredient in marijuana. So they have to be forcibly injected with it, unlike coke or opioids, which they will happily press levers to receive.

However, stress itself—like, say, being shot up with a drug that makes you anxious and paranoid repeatedly—is a well-known risk factor for addiction. And of course, no one actually shoots marijuana. What these studies mainly suggest, then, is that stressed rats are at greater risk of addiction, rather than stoner rats. In fact, a recent study on rhesus monkeys suggests that being forced to take marijuana may actually make taking heroin less attractive and rewarding—and monkeys are a far closer model to humans than rats are.

Given these realities, regarding marijuana as a special pharmacological "gateway" to other drugs is about as sensible as seeing lullabies as a "gateway" to Insane Clown Posse. Yes, all types of music lovers tend to start with kids' tunes during childhood, but what makes someone into a passionate fan with unusual taste isn't merely raw musical exposure.

The most intense enthusiasts of any type of activity tend to try a variety of similar experiences. Wine lovers don't stick only to pinot noirs, and art aficionados check out more than just Picassos. The same is true of drug users: The first experience doesn't make the fan. Instead, taste develops in a social, psychological and biological context where people choose whether or not to repeat it.


Further, as with other forms of compulsive behavior, the reason an activity can go from being a source of joy or calm to a desperate need isn't necessarily inherent in the experience itself. No one would suggest that we try to treat obsessive hand-washing by banning first soap and then hand sanitizer, or stop cat collectors by making kittens illegal. But we do the equivalent in the war on drugs.

The gateway idea prevents us from making sense of addiction. Instead, we need to look at what makes the minority who do become addicted different from all those experimenters who don't. For one, a large proportion of people with addictions—at least half—are addicted to more than one substance.

This suggests a propensity to seek escape in general: if you have already discovered that your use of a substance is causing problems, why try another one that might make things even worse? Frequently, people with addictions try many different classes of drugs—stimulants, psychedelics, depressants—a variety that makes no sense if it is being driven by a particular drug changing the brain rather than by a person looking for the best way to manage her consciousness.

And in fact, one common reason that people seek numbness or oblivion is that they have a mental illness, which makes them feel apprehensive, disconnected or unhappy. More than half of all people with addictions have an additional psychiatric disorder.


Nearly all mental illnesses are linked with higher risk for addiction, from attention deficit/hyperactivity disorder (ADHD) to mood disorders, anxiety disorders and schizophrenia. In the vast majority of these cases, the psychiatric problem is not caused by the drug use, and studies that follow children into adulthood repeatedly show that those who wind up with addictions tend to have emotional and behavior issues that were often visible as early as preschool. This suggests genetic or perhaps early environmental risk.

Crucially, the nature of the problems that predispose people to addiction varies widely—there is no single "addictive personality" that creates vulnerability. Instead, those who are addiction-prone tend to be outliers on different, sometimes opposing dimensions. For example, shy, anxious and withdrawn kids are at risk—but so are those who are wild and impulsive.

Another critical factor is childhood trauma. Each exposure to extreme stress raises risk: from sexual, physical and emotional abuse to neglect, witnessing violence and death, losing one or both parents or facing severe illness or disaster, the more trauma a child experiences, the greater the odds of addiction. One study, for instance, found that children who had been exposed to four or more different types of what are known as "adverse childhood experiences" had a 700 percent increased risk of alcoholism, compared to those with no adverse experience. In terms of smoking, those with four or more trauma exposures had a risk that was doubled to quadrupled, compared to those with none.


Socioeconomic status can also affect addiction liability. While the American press mostly seems to focus much on addiction when it's framed as middle class problem—like the ongoing heroin scare—the fact is that those at the highest risk are the poor. If you make less than $20,000 a year, your risk of heroin addiction is roughly three times greater than if you make $50,000 or more—and similar figures are seen with other substance use disorders.

Marijuana isn't the gateway to addiction: that's far more likely to be trauma, mental illness, or socioeconomic distress. Most people who smoke pot neither become addicted to it, nor to any other drug. Addiction is a relationship between a person, their genetics, their childhood experiences, their social and economic world, and a substance or activity. Not all addicted people will have all risk factors, and not all of those who are vulnerable will get hooked.

And because marijuana use (and even addiction) is associated with far fewer negative consequences than other drugs, researchers have suspected for years that many heroin and cocaine addicts actually use cannabis to help them reduce addiction-related harm.

I reported on research in this area related to crack for Alternet back in 2001. Ethnographic data suggested that older crack smokers gradually replaced their cocaine smoking with cannabis, while young users smoked weed instead of the crack that they'd seen harm their older siblings or parents.


Two newer studies further suggest possible uses for marijuana in treating opioid addiction and alcoholism. The first was a controlled trial looking at whether adding synthetic THC to an anti-opioid medication could help people seeking abstinence from heroin or prescription medications. It showed that while the synthetic THC didn't improve treatment retention, it did reduce withdrawal symptoms. More intriguingly, however, the study also found that participants who chose to smoke pot on their own—regardless of whether they got the synthetic THC or placebo—had much less anxiety and insomnia and were less likely to drop out of treatment.

The second study surveyed medical marijuana users in Canada, finding that 87 percent used it to replace alcohol, prescription opioids or other illegal recreational drugs. 52 percent said that it helped them reduce alcohol use, while 80 percent reported using fewer prescription pain medications. While most of the people in this study were not using the drug to treat addiction per se, those who had past addiction treatment reported were twice as likely to report replacing other illegal drugs with medical marijuana and equally likely to use it instead of alcohol or prescription medications.

The idea that marijuana is a gateway to addiction has blinded us both to its medical usefulness and to the real causes of addiction. Unless we start looking at what really puts people at risk, America will continue to promote solutions like wars on drugs that cannot prevent or treat addiction. As long as there are people who are without comfort and purpose in life, there will be others willing to sell them products—legal or otherwise— that promise escape.

Put another way, if you aren't looking for a way out, you won't find it.

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