Sunday, April 14, 2013

Marijuana and the Gateway Hypothesis


Smoke pot, shoot smack?

The Great Gateway Hypothesis has had a long, controversial run as a central tenet of American anti-drug campaigns. As put forth by Denise B. Kandell of Columbia University and others in 1975, and refined and redefined ever since, the gateway theory essentially posits that soft drugs like alcohol, cigarettes, and marijuana—particularly marijuana—make users more likely to graduate to hard drugs like cocaine and heroin. What is implied is that gateway drugs cause users to move to harder drugs, by some unknown mechanism. The gateway theory forms part of the backbone of the War on Drugs. By staying tough on marijuana use, policy makers believe they will have much broader impacts on hard drug use down the road.

This notion is virtually an article of faith in the drug prevention community. It just feels intuitively right: Scratch a junkie, and you’ll find a younger, embryonic pot smoker or furtive teenage drinker. Ergo, prevent teen pot smoking, and you will block the blossoming of a multitude of future hard drug addicts.

For years, the gateway hypothesis has had its share of contentious opponents. The countervailing theory is known primarily as CLA, for Common Liability to Addiction, the genetically based approach that lines up with the notion of addiction as a chronic disease entity. Most genetic association studies have failed to record risk variations for addiction that are specific to one addictive drug. Writing last year in Drug and Alcohol Dependence, Michael M. Vanyukov of the University of Pittsburgh, along with a large group of prominent addiction researchers, argued that the gateway hypothesis is essentially a form of circular reasoning. “It is drug use itself that is viewed as the cause of drug use development,” they write. The staged progression from one drug to another “is defined in a circular manner: a stage is said to be reached when a certain drug is used, but this drug is supposed to be used only upon reaching this stage. In other words, the stage both is identified by the drug and identifies the drug. In effect, the drug is identical to the stage.”

The researchers reject any causal claims on behalf of the gateway hypothesis and insist there is no necessary usage of soft drugs at an earlier stage to pave the way for hardcore addiction, however watertight the idea might sound. The high correlations are “artifactual,” they argue, “because they are estimated among hard drug users, without taking into account the large population of those who try or even habitually use marijuana but never transition to harder drugs.” A common cause, such as an underlying vulnerability to all drugs of abuse, seems more to the point, they insist. There is nothing out there to suggest that “these stages are either obligatory or universal, nor that all persons must progress through each in turn… the initiation order is frequently reversed even for the licit-to-illicit sequence.” There is only one stage that universally precedes hard drug use, they argue. And that is non-use. “It is the non-use then, which should be the actual gateway condition.”

The leading theory supporting the gateway hypothesis is that some as yet undetermined mechanism of “sensitization” occurs after using a gateway drug. But there is no science supporting this notion. “If sensitization does occur,” the researchers say, “it is equivalent to an increase in individual liability at the level of neurochemical mechanisms of addiction.”

The paper in Drug and Alcohol Dependence notes that in Japan, where marijuana is used by less than 5 percent of young people, “cannabis is not used first by a staggering 83.2% of the users of other illicit drugs, thus violating the gateway sequence.” Japan also handily knocks down the idea of alcohol as a gateway drug: Whereas the prevalence of aldehyde dehydrogenase deficiency—the so-called alcohol flush reaction—keeps many Asians from drinking alcohol regularly, this does not correlate with lower rates of non-alcohol substance use in that population.

All of this would seem to put the last nail in the notion that “involvement in various classes of drugs is not opportunistic but follows definite pathways,” as Vanyukov et. al. put it. Common sense seems to be ahead of official drug policy in this regard. According to Maia Szalavitz, writing at TimeHealthland, “only 38% of people now agree with the idea that ‘for most people, the use of marijuana leads to the use of hard drugs’ compared to 60% in 1977.”

For proponents of common liability to addiction models, any staged sequencing of drug use is considered opportunistic and trivial. Which, interestingly, is how many addicts tend to view the gateway theory. But the idea of marijuana or alcohol as a gateway drug just feels intuitively correct to many people. Part of the problem is chronological. “At the relatively distal time when genetic relationships are usually evaluated,” the authors maintain, “the role of this early-acting factor may be as difficult to detect as it is to find a match that started a forest fire.” Your genetic endowment is with you from birth, while your first drink or toke of marijuana does not happen for a decade or two. Individual environmental conditions, from epigenetic changes to a move to a different neighborhood, determine how it will play out down the road, but these factors are mostly invisible at the time of addiction.

All of this matters from a policy point of view, because research “may be hindered or misdirected if a concept lacking substance, validity and utility is accorded prominence.” However, even when the gateway hypothesis is taken as a given, different legal and social outcomes are still possible. The best example is found in The Netherlands. The prevailing belief there is that “the pharmacological effects of cannabis increase adolescents’ likelihood of using other drugs,” as stated  by Wayne Hall, a professor of public health policy at the University of Queensland, Australia. Writing in Addiction, Hall says that drug policy analysts in The Netherlands have argued that the fabled gateway “is a consequence of the fact that cannabis and other illicit drugs are sold in the same black market; they have advocated for the decriminalization of cannabis use and small retail sales in order to break the nexus between cannabis use and the use of other illicit drugs.”

This “Marijuana Shop” approach may have direct relevance in the U.S., in the wake of cannabis legalization in Washington and Colorado. James Anthony, a professor of epidemiology at the Bloomberg School of Public Health at Johns Hopkins, writes about the real-world ramifications of the cannabis shop in Addiction: “Do we actually achieve a near-term delay in the time to a young person’s first chance to try cocaine or heroin... [or] do we run the risk of accumulating more cases of dependence on marijuana, or other hazards attributable to non-essential marijuana use?

The true gateways to addiction appear to be behavioral. As part of their genetic endowment, budding addicts are far more likely than other people to exhibit behavioral “dysregulation” when young, in the form of disinhibition, impulsivity, and antisocial behaviors. More than half of all addicts are co-morbid, meaning they also have a psychological or behavioral disorder in addition to addiction. Further analysis of this fact would seem to be a more fruitful research avenue than simply prodding at alcohol or marijuana in an effort to uncover their chemical “secrets” for compelling future drug use.

Photo Credit: http://tcktcktck.org/ Creative Commons: Randi Shooters, 2010

2 comments:

peterreynolds said...

We need to stop this stupid and unwinnable war against cannabis. It is causing far more harm to our communities than it prevents. If we had a properly regulated system of production and supply we'd have no more illegal and dangerous cannabis farms causing fires and blighting communities. Instead we'd have thousands of new jobs. We'd have no more dealers on the streets. Cannabis would be available to adults only through licensed outlets and we'd have some control over its content and who it is sold to.

Doctors would be able to prescribe one of the most effective medicines that has no serious side effects at all. At the moment the UK government has given GW Pharmaceuticals an unlawful monopoly on cannabis so they make millions out of a medicine that anyone can grow at home for pennies.

If we introduced a legally regulated system we would solve nearly all the problems around cannabis. Science proves how much safer it is than tobacco, alcohol, prescription medicines and all other recreational drugs. If anyone does have a problem with it they could get help without having to confess to a crime.

CLEAR published independent, expert research last year which shows that a tax and regulate policy on cannabis would produce a net gain to the UK economy of up to £9.3 billion per annum.

It is a scandal that our government, our judges, our courts, our police and our newspapers keep misleading us about cannabis. Find out the truth for yourself. A huge disinformation campaign funded mainly by the alcohol industry has been misleading the British people for more than 50 years.

Brian Shapiro said...

From what I've read, gateway theory, as proposed by Denise Kandel, didn't argue a causal link between using one drug and another, just that there was a statistical association, and it was admitted that the association may be based on environmental factors rather than anything having to do with the drug. That is, the association of marijuana with hard drugs on the black market doesn't disprove the gateway effect it just proposes an interpretation of it.

Gateway theory replaced what was known as stepping-stone theory which did propose a causal link. The word 'gateway' was used to suggest that use of one drug simply facilitated, or 'opened the door' so to speak to use of another, but didn't make anyone go through it.

You could in theory reconcile the gateway and behavioral disposition approaches, by saying that misuse of alcohol, tobacco, or cannabis, is a warning sign and intervention at those stages can prevent the disposition from moving to harder drugs.

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