Is Marijuana a ‘Gateway Drug’?

Check out this answer from Consensus:

The evidence reviewed suggests that marijuana is not a reliable gateway drug leading to the use of harder substances. Alternative explanations, such as the common-factor model and developmental trajectories, provide plausible accounts for the observed associations between marijuana and other drug use. Additionally, the role of alcohol as a potential gateway drug and the impact of medical marijuana legalization further complicate the gateway hypothesis. Overall, the findings indicate that marijuana use alone is unlikely to be the primary cause of subsequent illicit drug use.

The concept of marijuana as a “gateway drug” has been a topic of significant debate and research. The gateway hypothesis suggests that the use of marijuana may lead to the use of more harmful and illicit substances. This article reviews the current literature to assess whether marijuana use indeed serves as a gateway to harder drugs.

The Marijuana Gateway Hypothesis

The marijuana gateway hypothesis (MGH) posits that marijuana use increases the likelihood of subsequent use of harder substances. A study using a nationally representative sample and propensity score-matching methodology found weak effects of frequent marijuana use on illicit drug use, but these effects were sensitive to hidden biases. The study concluded that marijuana use is not a reliable gateway cause of illicit drug use, suggesting that prohibition policies may not effectively reduce illicit drug use1.

Common-Factor Model

An alternative explanation to the gateway hypothesis is the common-factor model, which suggests that the association between marijuana use and the initiation of hard drugs is due to a common propensity to use drugs rather than a causal relationship. A model constructed using US household survey data demonstrated that the phenomena supporting the gateway effect could be explained by this common-factor model, indicating that no gateway effect is required to explain the observed associations2.

Developmental Trajectories

Research using data from monozygotic (MZ) and dizygotic (DZ) twin pairs examined the role of earlier marijuana use on later hard drug use. The study found that differences in earlier marijuana use predicted later hard drug use differences for DZ twin pairs but not for MZ twin pairs. This suggests that the pattern of drug use interpreted as the gateway effect might be better conceptualized as a genetically influenced developmental trajectory rather than a direct causal effect5.

Cross-National Comparisons

A study using data from the World Health Organization (WHO) World Mental Health Surveys compared patterns and order of initiation of drug use across 17 countries. The findings indicated that the gateway pattern reflects unmeasured common causes rather than causal effects of specific drugs on subsequent use of others. This implies that preventing the use of specific gateway drugs may not lead to major reductions in the use of later drugs7.

Perspectives from Users

Qualitative interviews with current and former marijuana users revealed mixed perceptions about marijuana as a gateway drug. While some participants supported the gateway concept, others did not, and many had conflicting views. This variability in perceptions highlights the complexity of the issue and suggests that individual experiences and beliefs play a significant role in shaping opinions about the gateway hypothesis8.

Alcohol as a Gateway Drug

Interestingly, some research suggests that alcohol, rather than marijuana, may serve as the initial gateway drug. A study of US 12th graders found that alcohol use was a stronger predictor of subsequent use of tobacco, marijuana, and other illicit substances. This finding supports the idea that alcohol should receive primary attention in substance abuse prevention programs4.

Medical Marijuana and Heroin Use

The legalization of medical marijuana has raised questions about its potential role as a gateway drug. A study examining the effect of medical marijuana legalization on heroin use rates found a generally negative but statistically insignificant effect. This suggests that while medical marijuana legalization may not reduce heroin use, it does not act as a gateway to heroin either10.

Is marijuana a ‘gateway drug’?

Luke Chu has answered Unlikely

An expert from Victoria University of Wellington in Economics, Econometrics, Health

Recent empirical evidence finds little causal evidence that marijuana use increases hard drug use. For example, Wen et. al (2015) show that while marijuana use had increased after the passage of medical marijuana laws, use of other substances like cocaine and heroin did not increase. Chu(2015) finds a similar result and that heroin treatment admissions had decreased after the passage of medical marijuana laws. Powell, Pacula, and Jacobson (2018) show that medical marijuana states experience a relative decrease in opioid addictions and opioid overdose deaths. In fact, even the original proposer of the gateway hypothesis, Denise Kandel, suggests that the existing evidence for the gateway effect is at best mixed, because of the lack of a clear neurological mechanism (Kandel 2003).

Is marijuana a ‘gateway drug’?

Stuart Taylor has answered Unlikely

An expert from Liverpool John Moores University in Drug Use

The notion of any drug being a gateway to another is a fundamentally flawed concept which sees a nonsensical focus on select substances and select outcomes – for example, do we see giving Calpol to babies with teething problems as a gateway to later pharmaceutical opioid use?; do we see tea and coffee use in childhood as a gateway to later alcohol use? In terms of marijuana, should this be seen as a gateway to, for example, heroin use? Absolutely not. A minority of marijuana users will go onto to use other illegal substances but the vast majority will not use the drug more than a few times or will not undertake any further experimentation. Given this context, it actually makes more sense to ask whether marijuana is a closing door drug, which ends drug using careers/trajectories rather than ratcheting them up. We could even hypothesize whether trends such as better quality marijuana use being available reduces the numbers of young people progressing to heroin use – whilst there is no evidence to suggest this is the case, it is an equally tenable suggestion as marijuana being a gateway to other substance use.

Is marijuana a ‘gateway drug’?

Charles Ksir has answered Unlikely

An expert from University of Wyoming in Neuroscience

This argument is based on data showing that most people who use cocaine or heroin used marijuana before they used those “hard” drugs. The other side of that argument is that most people who have tried marijuana have never gone on to try “hard” drugs. Marijuana is by far the most popular and most available illicit drug, so it stands to reason that the folks who are inclined to use illicit drugs will be most likely to encounter marijuana first–but there is no pharmacological reason that marijuana use would cause a person to crave or need a stimulant or opioid. A possible “gateway” is that a person who buys marijuana from an illicit dealer or becomes part of a drug subculture might be more likely to be exposed to other drugs and therefore be more likely to try them.

Is marijuana a ‘gateway drug’?

David Gangitano has answered Unlikely

An expert from Universitat de Barcelona in Botany, Genetics, Forensic Science

No, from my point of view as toxicologist and neuroscientist. I think that drug users would end using their drug of preference even without starting with cannabis. Cannabis does not create addiction such as other drugs (nicotine, cocaine, heroin).

Is marijuana a ‘gateway drug’?

Gary Potter has answered Extremely Unlikely

An expert from Lancaster University in Cannabis, Criminology, Drug Use

The idea that legalising cannnabis will inevitably lead people to using harder, more dangerous drugs is ridiculous. Although the majority of users of ‘hard’ drugs will have used cannabis previously, the majority of people who use cannabis do not go on to use harder drugs. One way in which cannabis use may be a contributory factor to use of harder drugs is through social and cultural networks – where the market for cannabis overlaps with the market for harder drugs (e.g., through overlapping networks of dealers) cannabis users may become exposed to opportunities to also purchase other illegal substances. Legalising cannabis would actually weaken this one area where the ‘gateway’ effect may operate – this was the rationale behind the Dutch ‘coffeeshop’ system which aimed to separate the markets for ‘soft’ drugs (i.e., cannabis) and ‘harder’ drugs.

Is marijuana a ‘gateway drug’?

Kerry Green has answered Uncertain

An expert from University of Maryland in Public Health, Drug Use

The question of whether marijuana is a gateway drug is complicated and depends on how you define “gateway.” There is much evidence that those who use marijuana are more likely to use other substances and often in a particular order (e.g., alcohol/tobacco, then marijuana, then cocaine), but it isn’t totally clear if marijuana increases the risk of other drug use or if this association is mostly driven by risk factors that lead to marijuana use and access issues.

Research has provided some evidence in rodents that marijuana may prime the brain to make it more susceptible to dependence on other drugs. Evidence is humans is mostly observational, but researchers are concerned that marijuana use, especially early in the life course, may make an individual more susceptible to more addictive drugs like opioids and cocaine. Alternatively, if recreational marijuana is legalized, the connection between marijuana and other drugs may lessen as individuals would be interacting less with drug markets and therefore should have less access to other drugs.