Policy Analysis | April 2016

Marijuana Use: Uncertainty on All Sides Continues

Sujit CanagaRetna

State legislatures continue to grapple with the myriad issues surrounding the legalization of medical marijuana as well as recreational marijuana. The following reflects a sampling of the research, articles and studies seeking to address questions related to whether marijuana and other substances are ‘gateway’ drugs. This information was compiled in response to an inquiry from a legislator in an SLC state.

A report from the National Institutes of Health’s National Institute on Drug Abuse.  There are several references embedded in the report that provide scientific details on whether marijuana is a gateway drug.

A study, Probability and Predictors of the Cannabis Gateway Effect: A National Study, published in February 2015 in the International Journal of Drug Policy, maintains that the predictors of progression from cannabis to other illicit drugs remain largely unknown.

Another 2015 study in the International Journal of Drug Policy entitled, The Effect of Medical Cannabis Laws on Juvenile Cannabis Use, concludes that there is little empirical evidence to support the view that medical cannabis laws affect juveniles' use of illicit non-cannabis drugs.

An October 2015 article in the Chicago Tribune indicates that a University of Florida study found that alcohol - not marijuana - is the gateway drug that leads adolescents down the path toward more serious substances.

In a posting entitled Why Nicotine is a Gateway Drug, the NIH maintains that “Nicotine, the researchers found, makes the brain more susceptible to cocaine addiction. The finding suggests that lowering smoking rates in young people might help reduce cocaine abuse.”

A scholarly article in the New England Journal of Medicine entitled A Molecular Basis for Nicotine as a Gateway Drug.  This article was co-authored by Eric R. Kandel, M.D, the 2000 Nobel Prize Winner in Medicine.

A Washington Post article on those “gateway drugs” that are legal, i.e., alcohol and tobacco.  There also is a comparison of alcohol, tobacco and marijuana in the article.  The study cited in this article demonstrates that of these three main substances -- alcohol, tobacco and marijuana -- children were the least likely to start using pot before the others.

According to the NIH, many factors affect drug use, such as genetic predisposition, mental health, history of trauma, and home environment. Furthermore, these factors affect other risk behaviors. In all, research on the subject is inconclusive, it is not clear whether later use of harder drugs after early onset use of marijuana is due to a biological reaction to the marijuana itself, or due to other factors common to risk behaviors. Research generally supports that early onset use of marijuana in adolescence affects the strength of predicted, later drug use.  

A 2014 selective review of genetic influences in marijuana and other drug use suggests that genetic and socio-environmental factors are more likely the cause of later use of harder drugs and mental illness, rather than prior use of marijuana. While causal mechanisms are unclear, the review found several studies confirming an increased risk of the use of hard drugs following early onset use of marijuana, even when controlling for early tobacco use, early alcohol use, general issues of conduct, and depression and social anxiety. However, “as this association remained in a sample for whom cannabis was legal, the previously observed associations between cannabis and other drug use could not be explained by the legal status of cannabis.” A similar study to those reviewed supports these findings and, in reviewing the literature, finds diverse explanations for the progression from tobacco to marijuana to other illicit drugs, but that evidence for reverse gateway effects (where marijuana use precedes tobacco use) supports a common factor model.

Another analysis, by RAND Corporation, similarly regards the gateway theory as inconclusive, supporting a common-factor model, and notes: “Some might argue that as long as the gateway theory remains a possible explanation, policymakers should play it safe and retain current strictures against marijuana use and possession. That attitude might be a sound one if current marijuana policies were free of costs and harms. But prohibition policies are not cost-free, and their harms are significant: The more than 700,000 marijuana arrests per year in the United States burden individuals, families, neighborhoods, and society as a whole.”

Legalized medical marijuana has quickly spread to nearly half the U.S. states. But safety regulations lag behind, leaving medical pot users with questions about side effects.

New study finds that, with more permissive state laws, marijuana use is up ‐ and so is addiction to the drug.

Medical marijuana push criticized by Georgia prosecutors.