Is Marijuana a “Gateway Drug”?

For many years, opponents of marijuana policy reform have claimed that while marijuana itself may not be as dangerous as so-called “hard drugs” like cocaine or heroin, it is a gateway drug that leads users down a path toward use of those more dangerous substances. This, despite the fact over 107 million Americans — more than 40% of the U.S. population born since 1960 — have tried marijuana, yet only 37 million have tried cocaine, only four million have ever tried heroin, and less than one-tenth of one percent of Americans used either in the last month. Fortunately, science has weighed in, and nearly every researcher who has ever looked into the question has determined that marijuana use is not a causal factor in the subsequent use of more dangerous drugs. Rather, marijuana is simply the first (or more likely, third, after alcohol and cigarettes) in a normal progression to more dangerous substances among those predisposed to use such drugs.

In fact, some researchers believe that it is marijuana’s illegal status that is the real gateway. Because marijuana is illegal, those who seek to buy it must obtain it from criminal drug dealers who often maintain an inventory of other drugs and have an incentive to expand their market to new users. This exposure to the illicit market — and peer groups that are willing to engage in drug use — can lead individuals to use of more dangerous drugs. Researchers also identified socio-economic factors like employment and educational attainment influence the likelihood of substance abuse. Marijuana’s illegal status means that an arrest for marijuana possession, and the collateral educational and employment consequences that come with it, could lead to later substance use.

Here is a small sampling of the many peer-reviewed studies debunking the so-called “gateway theory”:

Predictors of Marijuana Use in Adolescents Before and After Licit Drug Use: Examination of the Gateway Hypothesis

Predictors of Marijuana Use in Adolescents Before and After Licit Drug Use - Examination of the Gateway Hypothesis Tarter, et al. American Journal of Psychiatry (2006) – “This evidence supports what’s known as the common liability model … [which] states [that] the likelihood that someone will transition to the use of illegal drugs is determined not by the preceding use of a particular drug, but instead by the user’s individual tendencies and environmental circumstances,” investigators stated in a press release. They added, “The emphasis on the drugs themselves, rather than other, more important factors that shape a person’s behavior, has been detrimental to drug policy and prevention programs.”

http://ajp.psychiatryonline.org/article.aspxVolume=163&page=2134&journalID=13

Reassessing the Marijuana Gateway Effect

Reassessing the Marijuana Gateway Effect Morral, et al. British Journal of Addiction (2002) – “We’ve shown that the marijuana gateway effect is not the best explanation for the link between marijuana use and the use of harder drugs … An alternative, simpler and more compelling explanation accounts for the pattern of drug use you see in this country, without resort to any gateway effects. While the gateway theory has enjoyed popular acceptance, scientists have always had their doubts. Our study shows that these doubts are justified.”

http://www.rand.org/pubs/research_briefs/RB6010/index1.html

A Life-course Perspective on the “Gateway Hypothesis”

A Life-course Perspective on the “Gateway Hypothesis” Van Gundy & Rebellon, Journal of Health and Social Behavior (2010) – “Our results indicate a moderate relation between early teen marijuana use and young adult abuse of other illicit substances; however, this association fades from statistical significance with adjustments for stress and life-course variables.

Likewise, our findings show that any causal influence of teen marijuana use on other illicit substance use is contingent upon employment status and is short-term, subsiding entirely by the age of 21. In light of these findings, we urge U.S. drug control policymakers to consider stress and life-course approaches in their pursuit of solutions to the ‘drug problem.’”

http://hsb.sagepub.com/content/51/3/244.short

Marijuana and Medicine: Assessing the Science Base

Marijuana and Medicine- Assessing the Science Base Joy, et al. for the Institute of Medicine, part of American Academy of Sciences, National Academies Press (1999) – “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. … [I]t does not appear to be a gateway drug to the extent that it is the cause or even that it is the most significant predictor of serious drug abuse; that is, care must be taken not to attribute cause to association. There is no evidence that marijuana serves as a stepping stone on the basis of its particular physiological effect … Instead, the legal status of marijuana makes it a gateway drug.”

http://www.nap.edu/openbook.php?record_id=6376&page=6

Understanding the Association Between Adolescent Marijuana Use and Later Serious Drug Use: Gateway Effect or Developmental Trajectory?

Understanding the Association Between Adolescent Marijuana Use and Later Serious Drug Use- Gateway Effect or Developmental Trajectory? Cleveland & Wiebe, Development and Psychopathology, Cambridge University (2008) – “Because marijuana use often precedes the use of other psychoactive substances, it has been characterized as a gateway to these other substances.

Using data from twin pairs drawn from the National Longitudinal Study of Adolescent Youth this study examines the “gateway effect” role of earlier marijuana use on later hard drug use. Rather than supporting the interpretation that earlier marijuana use ‘triggers’ later hard drug use, the results suggest that the longitudinal pattern of drug use that has been interpreted as the ‘gateway effect’ might be better conceptualized as a genetically influenced developmental trajectory.”

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=1842736

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