what hypothesis states that marijuana leads to abusing other drugs?

Chris Christie said that marijuana is a "gateway drug" while arguing for enforcement of its federal status as an illegal substance. Though there are correlations between marijuana use and other drugs, at that place is no conclusive bear witness that ane really causes the other. The science on this topic is far from settled.

In an interview on Hugh Hewitt'southward radio testify on April 14, Christie, the governor of New Jersey and a potential 2016 presidential candidate, said he would crevice down on marijuana sales and use in Washington and Colorado, which in 2012 were the starting time two states to legalize marijuana for recreational use. "Marijuana is a gateway drug," Christie said. "We have an enormous addiction problem in this country."

The "gateway hypothesis" or theory refers to the idea that one substance — marijuana, in this case — leads users to subsequently use and/or corruption other drugs. If Christie'due south point is simply that the utilise of marijuana tends to precede the use of other drugs, then he is correct — but that'due south not the whole story.

Though studies of large populations of people have indeed found that those who smoke marijuana are more probable to use other drugs, these studies show a correlation without showing causation — a commonly misunderstood miracle in science. In short, but considering marijuana smokers might be more than likely to later use, say, cocaine, does not imply that using marijuana causes one to use cocaine.

A 1999 study from the Institute of Medicine, which is office of the National Academy of Sciences, laid out this issue clearly (meet pages 100-101): "In the sense that marijuana use typically precedes rather than follows initiation into the employ of other illicit drugs, it is indeed a gateway drug. Still, it does not announced to be a gateway drug to the extent that information technology is thecause or even that information technology is the most significant predictor of serious drug abuse; that is, care must exist taken not to attribute crusade to association."

Nosotros spoke with several experts and reviewed the bachelor scientific literature on gateway theory. Christie'south definitive statement is unsupported past evidence — there is some bear witness in favor of a gateway effect, merely the scientific community shares no consensus on the issue and there is footling bear witness on the underlying crusade of that consequence.

Biological Mechanisms

Chiefly, at that place are two distinct ways in which marijuana or other drugs might act every bit a gateway: biological or pharmacological reasons why marijuana would pb to other drugs (sometimes known equally the "stepping stone" theory); and social or cultural reasons for the bound from one drug to another. In the case of the beginning idea, some enquiry has found plausible biological ways in which marijuana — and, notably, nicotine and alcohol — could "prime" the encephalon and make one more likely to abuse other drugs, but this enquiry is largely in rats and is not conclusive.

"There are some studies that have been done in animals and they suggest that at that place may be changes that marijuana produces in the brain that can be long lasting when the brute is exposed to it as an adolescent," said Susan Weiss, the acquaintance director for scientific diplomacy at the National Found on Drug Corruption, which is part of the National Institutes of Health, in a phone phone call.

For example, in one report published in 2007 in the journal Neuropsychopharmacology, researchers treated some adolescent rats with THC, the main active compound in marijuana. The rats were then given the opportunity to "self-administer" heroin as adults. The THC-treated rats consistently increased their heroin usage, while those rats that had non been treated with THC maintained a steady level of heroin intake.

Some other report, published in 2014 in European Neuropsychopharmacology, similarly plant that adolescent THC exposure in rats seemed to change the rodents' brains. The rats treated with THC exhibited more anxiety-like behaviors, and likewise exhibited more "heroin-seeking" behavior afterward in life. The authors concluded that, at least in rats, chronic exposure to THC during boyhood could indeed be responsible for "increased vulnerability to drug relapse in adulthood." Some other rat study, from Biological Psychiatryin 2004, besides found that THC exposure induced "cross-tolerance" that could increase later on usage of cocaine, morphine, and amphetamine.

Notably though, these findings are not unique to marijuana. Weiss told us that nicotine and alcohol, two other drugs that are widely available to young people and are often among the kickoff drugs used, have been found to have similar effects in beast studies. One such written report, published in the journalScience Translational Medicine in 2011, showed that treating mice with nicotine induced genetic changes that increased the response to cocaine. Interestingly, this only worked in 1 management, when the mice were treated with nicotine and and so co-treated with both nicotine and cocaine; if cocaine was administered first, the outcome was not seen, suggesting there may exist a gateway effect from nicotine to cocaine.

The studies on encephalon chemistry and the influence of marijuana on responses to other drugs only has taken place in those beast studies, meaning extrapolation to humans is problematic. Nosotros do have some hints of biological gateway effects in humans, though, from studies involving twins.

One such study, which was published in the Journal of the American Medical Association in 2003, and involved 311 twin pairs "discordant" for early marijuana utilize — that is, ane of each set of twins had used marijuana before the age of 17, and the other had not. The twin that did use marijuana early in life had between a ii.ane- and 5.2-times higher risk of other drug use, alcohol dependence, and drug abuse/dependence than their sibling. This means that associations betwixt marijuana utilize and after drug use tin't exist explained past genetic factors, and gives support to the gateway theory.

Simply even this leaves a lot of unanswered questions, according to Weiss. "Did marijuana change that twin and brand them more likely to use other drugs? What was it about that 1 twin that fabricated them use marijuana while the other twin didn't? We don't know the respond to that. Did he happen to have friends that were more deviant? It'south very hard to completely interpret these things; most likely there is probably some convergence of factors."

And indeed, a subsequent twin study published in Development and Psychopathology in 2008 called the results of the starting time into question. The paper plant a similar departure between twins with regard to early marijuana employ and later on drug utilise, but only in non-identical twins. To the authors, this supported the thought that there are likewise many factors to conclude in 1 management or the other: "[T]he longitudinal pattern of drug use that has been interpreted as the 'gateway upshot' might be better conceptualized as a genetically influenced developmental trajectory."

Hidden Causes and International Patterns

Clearly, the biological evidence for a gateway effect is varied and difficult to interpret. Unfortunately, specific evidence for the other possible mechanisms are also far from articulate and definitive.

The cultural and social version of the gateway theory posits that simply by beingness around marijuana and the people who use it one might be more likely to end upwards trying and using other drugs too. In that location is also the thought that an individual who uses marijuana habitually may but exist more likely to engage in adventure-taking behavior, and thus will seek out the other drugs. This would suggest there is no causal link from marijuana to other drugs, it is only a office of marijuana's full general availability versus other more difficult-to-obtain substances.

Some researchers, though, think there is nigh certainly a causal link — it's simply non clear what it is. David Fergusson is a professor at the University of Otago in Christchurch, New Zealand, and he has been leading the Christchurch Health and Development Study, a 35-yr, ongoing look at 1,265 New Zealanders born in 1977. Several papers on drug apply and the gateway effect have emerged from this study.

"There is a very strong clan between the employ of cannabis in adolescence and subsequent utilize of other illicit drugs," Fergusson told united states of america in an electronic mail. He said that i analysis from his study published in the journal Habit used a statistical test that "clearly suggest the existence of some kind of causative association in which the use of cannabis increases the likelihood that the user will go on to use other illicit drugs. … Where things get murky is in the area of the nature of the causal processes."

Another possible contributor to those processes is simply the availability of a given drug that might lead information technology to be used first, rather than any item biological reason for moving from one to another. A large international collaboration produced a written report published in the journal Drug and Alcohol Dependence in 2010 that looked at patterns of drug use across 17 countries. The study constitute that "[w]ith few exceptions, substances earlier in the 'gateway' sequence predicted drug use later in the sequence." That finding, though, differed in forcefulness across countries.

Those early-sequence drugs included marijuana, booze, or nicotine. Different countries had different patterns of drug apply in general, and also dissimilar patterns of gateway "violations" — that is, when people used other illicit drugs without ever trying those early on drugs. For instance, Japan had very low rates of marijuana use (i.6 percentage by age 29), and also had more people utilise other illicit drugs earlier the early-use drugs than in other countries. The authors wrote, "a lack of exposure and/or admission to substances earlier in the normative sequence did not represent to reductions in overall levels of other illicit drug use." In other words: limiting admission to marijuana might not have whatever event on heroin and cocaine use.

That report also provides a hint that marijuana'due south illegal status may contribute to its gateway effects. The mechanism here is simple: accessing one illegal drug simply means a marijuana user would exist more likely to have access to other illegal drugs, through social interactions and the act of actually ownership the drug. TheDrug and Alcohol Dependence report establish that marijuana utilize was less strongly associated with other illicit drug use in kingdom of the netherlands, where marijuana tin can legally be purchased in so-called coffee shops, than in other countries including the United States.

A working study from the Rand Drug Policy Inquiry Middle looked at the Dutch experience with legalized marijuana also. According to that paper, the U.S. actually has slightly college rates of employ than the Netherlands, and in that location is evidence for a "weakened gateway" in the Netherlands: about xv of every 100 cannabis users have tried cocaine in that country, a lower rate than others where marijuana is illegal such as Scotland, Italy, and Norway. The aforementioned is truthful for amphetamine utilize.

Fergusson told united states that more than enquiry is still needed to truly understand what the causal link between marijuana and other drugs might be. "It is my view that when the jury comes in, what will be institute is a complex multivariate situation in which the greater susceptibility of cannabis to illicit drug use is the terminate bespeak of a complex mix of factors including: the neurophysiological effects of cannabis; social and peer influences; and the legal status of cannabis," he said.

Weiss, of NIDA, said that scientifically a gateway effect cannot be ruled out, but a conclusive "yes" is besides not possible at this point. "The scientific community is however arguing well-nigh it," she told us. "It actually is a complicated thing to tease out. Information technology has been very contentious over the years. And I don't know how useful it is as a concept, simply information technology'south something that people latch on to."

Christie is entitled to his opinions on the legality of marijuana and the statutes in Washington and Colorado, and he is correct that marijuana use "typically precedes" the use of other illegal drugs, as the Plant of Medicine report said. But there is no firm ground to stand up on when making claims of the drug'due south gateway effect.

Editor's Annotation: SciCheck is fabricated possible past a grant from the Stanton Foundation.

– Dave Levitan

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Source: https://www.factcheck.org/2015/04/is-marijuana-really-a-gateway-drug/

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