The theory of weed as a gateway drug remains controversial. However, not all research supports this theory. Even studies suggesting people who use cannabis are more likely to use other drugs often fail to prove that cannabis directly leads to other drug use.

For decades, government and public health policies prioritized preventing cannabis use, including via criminalization, according to the theory of cannabis as a gateway drug. This notion argues that using cannabis increases the risk of using other drugs or that people who use cannabis become interested in additional drug use because of their cannabis use.

Some research suggests that people are more likely to use cannabis before using other drugs, while other studies indicate those who use cannabis have a higher lifetime risk of going on to misuse other drugs. Additionally, some studies have found that individuals who use cannabis before using other drugs may have a higher risk of developing a substance use disorder.

Keep reading to learn more about the cannabis gateway drug theory, including what the research says. This article also discusses some potential health benefits of cannabis and some other common myths about the plant.

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The gateway theory argues that cannabis use leads to the subsequent use and misuse of other “harder” drugs, which may include opioids, such as heroin, or stimulants, such as cocaine. Supporters of this theory argue that cannabis may act as a gateway in one or more ways, including:

  • Altering brain chemistry: The theory states that cannabis may change how the brain responds to other drugs. It may also increase the desire for drugs.
  • Altering addiction threshold: In this understanding of the gateway theory, cannabis use may change the amount of drugs a person must use before developing substance use disorder, making it easier to meet this criterion.
  • Environmental factors: In this understanding, individuals who use cannabis may be part of environments where drug use generally feels routine or where other drugs are available.

Is weed a gateway drug?

Cannabis research and policy remain highly politically charged. Those who favor prohibition argue that cannabis is extremely dangerous and leads to substance use disorder, and they seek to ban the substance and punish in possession of it.

In contrast, cannabis advocates argue that the drug is harmless and perhaps even beneficial, that banning it increases mass incarceration, and that the war against drugs has failed.

According to the American Civil Liberties Union, the war on drugs and cannabis contributes to excessive police stops and mass incarceration. Half of all drug arrests are for cannabis possession, and most arrests involve people using the drug for personal use, not distribution.

However, various sides of the argument disagree about whether cannabis is a gateway drug, and this includes scientific research.

What the research says

Some research in animals suggests that exposure to cannabis in early development may change the way the brain responds to drugs. Specifically, animal studies indicate that early exposure to cannabis could alter the brain’s response to dopamine, a brain chemical that helps drive substance use disorder. It could also make the brain respond more strongly to other drugs.

For example, in one preprint 2020 study, rats that had cannabis exposure during development had a range of changes in their brain that could increase the rewards associated with subsequent drug use. While the exposure to cannabis increased the motivation to seek cocaine, actual cocaine-related behaviors, such as taking cocaine or becoming addicted, did not change.

However, because these studies used rats and not humans, it is unclear whether cannabis has the same effect on people.

A 2020 paper reviewed decades of data pointing to cannabis as a gateway drug. Many of its cited studies did find a correlation, but they often also had serious methodological issues. For example, one study found that teenagers who use cannabis are 104 times more likely to use cocaine than those who do not. But there were significant differences between the two groups that predated their cannabis use. This suggests that some other environmental differences, differences in personality, or other risk factors, may explain the use of both drugs.

A 2021 study suggests that cannabis may serve as a gateway drug to opioid use. Drawing on a systematic review and meta-analysis of six studies involving 102,461 participants, researchers found a higher likelihood of opioid use and misuse among people who use cannabis. However, even the study’s authors advise that the quality of the evidence overall is low, so it is not possible to conclude that cannabis use causes the use or misuse of other drugs.

A 2021 nationally representative study used 18 tests to assess the theory of cannabis as a gateway drug. Six of these showed a statistically significant link between cannabis use and the use of other drugs, but only three showed substantive results. And the researchers caution that these three tests were subject to hidden bias, suggesting that their data does not provide evidence for cannabis as a gateway drug.

In the years following the legalization of cannabis in some states, many states saw a reduction in opioid misuse rates and overdoses. Some advocates argued that this meant people were using cannabis rather than opioids to control pain.

A 2019 study also found no evidence that recreational or medical uses of cannabis had associations with changes in opioid overdose mortality. However, the researchers also stated that while they felt studies into the health benefits of cannabis should continue, people should remain skeptical about the claim that medical cannabis laws will directly reduce opioid overdose and death. With this in mind, more research is necessary.

Overall, the research on cannabis as a gateway drug is not conclusive. Even studies that do show a link only show a very weak one or rely on low quality data.

Even if cannabis is a gateway drug, the evidence does not suggest that banning it works to stop other harmful drug use. In fact, some studies have even found that cannabis criminalization increases availability and use and puts more potent forms of the drug on the market.

Doctors seem to think that people can develop an addiction to cannabis. Individuals who use cannabis frequently may develop a dependence, especially if they begin using it at a young age. The lifetime risk of developing a cannabis addiction if a person uses cannabis is about 10%.

Learn more about whether cannabis is addictive.

Supporters of cannabis use and legalization point to its status as a natural substance. Many potentially harmful, even toxic, chemicals are natural. For example, some opioids come from the opium poppy plant. Tobacco, hemlock, and arsenic are also natural.

Overall, however, the dangers of cannabis compared with other drugs are likely lower. Aside from rare cases of allergic reactions, there have been no deaths directly due to cannabis use alone and no documented overdoses.

That said, cannabis may also have health benefits. The Food and Drug Administration (FDA) has approved a cannabis-based drug to stop seizures in people with a severe form of epilepsy.

The risks of cannabis use include:

  • cannabis hyperemesis syndrome, which causes bouts of vomiting and nausea
  • negative drug reactions such as fear, anxiety, or psychosis
  • lung damage, including potentially a higher risk of lung cancer
  • more frequent pain crises in people with sickle cell disease
  • preterm birth
  • addiction
  • decreased sperm production in males

Some other cannabis myths include:

  • Cannabis is safe when breastfeeding or pregnant because it is natural: Researchers do not know if cannabis is safe when breastfeeding, but the ingredients in the substance can pass to the baby in the mother’s milk. Using cannabis during pregnancy can also pass chemicals to the fetus, potentially undermining development.
  • Cannabis use may lead to dependence: Cannabis can lead to dependence, especially with prolonged and frequent use. Individuals who frequently use cannabis can also experience withdrawal symptoms when they quit.
  • Cannabis smoke is harmless: Cannabis smoke contains some chemicals that may damage the lungs. And while smoking cannabis does not increase the risk of emphysema, it may increase the risk of certain respiratory infections. It is unclear whether cannabis smoke damages the immune system or whether the negative effects are as severe as cigarette smoke.
  • Banning cannabis works: Banning cannabis has not decreased its use. Supporters of its legalization argue that banning the drug increases mass incarceration, leads to violence through the underground drug trade, and ignores the comparatively more severe effects of drugs such as alcohol.

People seeking help for their cannabis use or the conditions they use cannabis to manage should speak with a healthcare professional. Some signs that a person might need help include:

  • They want to stop using but cannot.
  • They experience painful withdrawal symptoms when they attempt to stop using cannabis.
  • They have an underlying medical condition and would prefer to use something other than cannabis to manage it.
  • They develop substance use disorder around another drug, such as opioids.

Seeking help for addiction may seem daunting or even scary, but several organizations can provide support. If you believe that you or someone close to you is struggling with addiction, you can contact the following organizations for immediate help and advice:

Cannabis increasingly has acceptance as a medication and not just a recreational drug.

Research around cannabis being a gateway drug remains inconclusive. Currently, there are not enough robust studies to support that it is a gateway drug.

Like all drugs and medications, it has potential risks and benefits. Very young people who use cannabis may be more vulnerable to its risks, including developing a substance use disorder.

It is important for all people who use or are considering using cannabis to weigh the risks and benefits and have an unbiased, evidence-based understanding of its effects. No drug is risk-free, and cannabis is no exception. However, the political rhetoric surrounding cannabis use has sometimes inflated its risks and minimized its benefits.