Is Marijuana a Gateway Drug? The Truth About the Gateway Theory

Many arguments support the hypothesis that cannabis is a hazardous substance which only leads to further drug abuse. This is dubbed as the gateway theory.

The term gateway drug is very simple to understand—gateway drug is a substance which ultimately leads one to experiment with more “advanced” and dangerous narcotics.

Gateway theory originally gained momentum during the cannabis prohibition era.

Arguments in favor of the gateway drug theory

Those who agree with this hypothesis say that people who have issues with hard drugs have used cannabis prior to trying those heavier drugs, and subsequently developed an addiction.

Some state agencies, like the National Institute on Drug Abuse (NIDA), often refer to a couple of studies in order to back up their views.

In a study published in 2004, scientists discovered that exposing “adolescent” rats to THC “decreases the reactivity of brain dopamine reward centers later in adulthood”. (1)

NIDA and authors of similar papers support their arguments with this particular study by saying that “this could help explain the increased vulnerability for addiction to other substances of misuse later in life that most epidemiological studies have reported for people who begin marijuana use early in life.” (2)

There’s one more thing in this study that is often mentioned and that’s a phenomenon called cross-sensitization.

Cross-sensitization is a process of transferring sensitization from one substance to a related substance, or in other words—one substance “prepares” the brain for an increased response to other similar substances.

In the previously mentioned study, the first substance that was given to rats was THC (the most abundant cannabinoid found in cannabis). The second substance that animals showed an intense behavioral response to was morphine. (3)

When you stop and think about it, it does makes sense to an extent. However, there is a solid counter-argument to be made here.

Arguments against the gateway theory

Cannabis is the most common and widely-available partially illicit substance.

It’s now considered partially illicit because at the moment there are a lot of countries (and US states) which legalized it, and even more that decriminalized it.

It is considered a soft drug since it’s not as addictive as some legal substances that you can simply walk in and buy in a store (for example alcohol).

Cannabis use around the world is growing:

According to recent polls, 52% of Americans over the age of 18 tried cannabis at least once in their lifetime, and as of 2018, 42.5% of Canadians over the age of 15 have also tried it at some point in their lives.

Some studies mention that nicotine and alcohol have the same cross-sensitization effect, so this isn’t something that’s unique to cannabis. (4)

Alcohol and tobacco, which are legal, also prime the brain for a heightened response to other more or less similar substances.

In 2016, researchers from the University of Florida wanted to determine which substance adolescent use first.

According to the study, which surveyed over 2.800 US twelve-graders, cannabis comes third after alcohol and tobacco. (5)

According to the study, 54% of adolescents first try alcohol, 32% tobacco and 14% start off with cannabis.

Cannabis as an “exit drug”?

Few studies point to cannabis as a solution to the opioid crisis, as the latter is a growing concern across the entire North America.

One 2017 review emphasized that, after the legalization in Colorado, the number of opioid and heroin-related deaths dropped by 20%. (7)

Also, according to the research conducted by the American Medical Association, states which legalized cannabis for recreational use now have 24.8% less opioid-related deaths than states where pot is still illegal. (8)

One interesting survey from 2017 presented a promising “substitution effect” of medical cannabis in battle with addiction in general. (9)

In that survey, dispensary customers from New England reported the following:

  • 77% of them said they reduced their use of opioids use after they began using medical cannabis;
  • 72% reported using fewer anti-anxiety medications;
  • 66% noted the reduction of migraine medications;
  • 65% reported reductions in sleep medications;
  • 42% reported reductions in alcohol consumption;
  • 38% reported reductions in antidepressants.

So, what’s the verdict?

Even though there are several studies that support the cannabis gateway theory, many other show that it is not likely. Furthermore, the numbers from states that legalized cannabis are firmly pointing in a direction that cannabis reduces opioid addiction rates.

We still don’t have nearly enough research on the topic and I hope future studies will be able to shine some light on this delicate question.

In the meantime, we should work towards preventing adolescent use of any of the 3 popular substances (alcohol, tobacco and cannabis).

References:

  1. Pistis M, Perra S, Pillolla G, Melis M, Muntoni AL, Gessa GL; Adolescent exposure to cannabinoids induces long-lasting changes in the response to drugs of abuse of rat midbrain dopamine neurons; Biological Psychiatry; 2004; 56(2):86-94
  2. Agrawal A, Neale MC, Prescott CA, Kendler KS; A twin study of early cannabis use and subsequent use and abuse/dependence of other illicit drugs; Psychological Medicine; 2004; 34(7):1227-1237
  3. Cadoni C, Pisanu A, Solinas M, Acquas E, Di Chiara G; Behavioural sensitization after repeated exposure to Delta 9-tetrahydrocannabinol and cross-sensitization with morphine;  Psychopharmacology; 2001; 158(3):259-266
  4. Levine A, Huang Y, Drisaldi B, Griffin EA Jr, Pollak DD, Xu S, Yin D, Schaffran C, Kandel DB, Kandel ER; Molecular mechanism for a gateway drug: epigenetic changes initiated by nicotine prime gene expression by cocaine; Science Translational Medicine; November 2011; 3(107):107ra109
  5. Barry AE, King J, Sears C, Harville C, Bondoc I, Joseph K; Prioritizing Alcohol Prevention: Establishing Alcohol as the Gateway Drug and Linking Age of First Drink With Illicit Drug Use; The Journal of School Health; January 2016; 86(1):31-38
  6. Livingston MD, Barnett TE, Delcher C, Wagenaar AC; Recreational Cannabis Legalization and Opioid-Related Deaths in Colorado, 2000-2015; American Journal of Public Health; November 2017; 107(11):1827-1829
  7. Bachhuber MA, Saloner B, Cunningham CO, Barry CL; Medical cannabis laws and opioid analgesic overdose mortality in the United States, 1999-2010; JAMA Internal Medicine; October 2014; 174(10):1668-1673
  8. Piper BJ, DeKeuster RM, Beals ML, Cobb CM, Burchman CA, Perkinson L, Lynn ST, Nichols SD, Abess AT; Substitution of medical cannabis for pharmaceutical agents for pain, anxiety, and sleep; Journal of Psychopharmacology; May 2017; 31(5):569-575
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