Is Cannabis a ‘Gateway Drug?

What is a Gateway drug

The fundamental proposition of the ‘Gateway drug hypothesis’ (also known as the ‘Gateway Effect’) is that people, usually the young, will start out by experimenting with Cannabis and that experience will inevitably end up with them taking harder drugs (such as Ice or Heroin) later in life.

The short answer is that the weight of the evidence available suggests that marijuana is not a gateway drug. The results are not clear cut, however which, together with personal bias and some subtlety in how the results of the tests that have been performed are interpreted means it’s an old argument which will likely be thrown around for some time. In reality, where cannabis has been legalized, use of ‘hard’ drugs has fallen.

So where does the Gateway Hypothesis come from?

There are 2 suggestions as to what might cause the Gateway hypothesis to be true.

• Taking marijuana affects the brain thereby encouraging the use of other drugs: 
  First, some suggest that taking marijuana influences users’ brains in such a way as to precondition them to pursue ever greater ‘high’s through increasingly risky drug experiments.
• Social exposure leads individuals down the path of drug experimentation:
  The second relates to peer groups, suggesting that being part of a marijuana culture exposes people to individuals with whom they may not otherwise engage – and that, as a result of those relationships, marijuana smokers are exposed to other, more dangerous drugs.

The problem with establishing the answer to the hypothesis is one of ethics. In order to get to the bottom of whether the hypothesis is true or not, you’d need to separate a lagre group of individuals in to 2 groups of people. One of them, you force marijuana on for a long time – then you see if they end up taking heavy drugs. The other group, you prevent having marijuana and watch to see if any of them take hard drugs. Then you compare the performance of the two groups. No ehtocs board in the world would sign that off.

Greg Hunt (Australian Minister) said recently in the news when commenting on the proposed legalization of recreational cannabis in Australia:  “Marijuana is a gateway drug. The risk of graduating to ice or to heroin from extended marijuana use is real and documented,” it’s a common ‘go to’ argument for some politicians.

To be fair to him, there was medical support for some concern when it came to the legalization of marijuana from the Australian Medical Association citing ‘significant reservations’ especially in younger age groups.

What’s the evidence that Cannabis is a Gateway drug?

The US NDIA (National Institute on Drug Abuse) presents some evidence to support the suggestion that taking marijuana ‘primes’ the brain to engage with other, harder drugs. In trials involving exposing younger rodents to cannabinoids reduces the sensitivity of the brain’s reward centers (dopamine) later in life.

The NDIA points out, however, that ‘priming’ of the sort witnessed in these experiments is not unique to marijuana and was experienced in rodents which were exposed to alcohol and nicotine, in similar tests.

No human trials have been performed to substantiate these findings. It’s not clear that if those tests were run in humans, they would get the same results.

MYTH: The weight of the evidence available suggests that marijuana is not a gateway drug.

Is there any evidence to the contrary?

The best evidence which is available is from a ‘natural’ experiment which has taken place anyway. In Colorado, the state which legalized recreational cannabis before anyone else. The data from Colorado suggest that the opposite of the Gateway Hypothesis is true. That is, when marijuana was legalized for recreational use in the state, a use of a number of ‘harder’ drugs declined. For example.

• Opioid prescriptions went down.
• Opioid overdoses fell.
• Teen abuse of heroin declined.

The evidence available from Colorado then, suggests that Cannabis is a something people use instead of (as a substitute for) harder drugs.

One suggestion as to why this negative correlation exists (i.e. more marijuana is used; less hard drugs are used) is the lack of a ‘drug dealer’ as a regular contact for people. Some suggest that these drug dealers make it easier for people who are buying cannabis to buy other drugs too. It’s also worth remembering that drug dealers are in the business of selling drugs – they actively pursue the goal of foisting drugs on their patrons. Legalizing recreational cannabis removes the dealer from the equation and therefore reduces the number of people who will take harder drugs from dealers.

More broadly, there are many millions of people in Australia and around the world who have tried cannabis and not gone on to try other, harder drugs, as The Drug Policy Alliance points out.

FACT: The data from Colorado suggest that the opposite of the Gateway Hypothesis is true. That is, when marijuana was legalized for recreational use in the state, a use of a number of ‘harder’ drugs declined.

Summing up the questions and answers on The Gateway Hypothesis

As with many questions surrounding cannabis, there is only a small amount of science available to inform discussion. In this sort of circumstance, it’s all too easy for either side of the debate to rely on anecdotes from their personal lives as being representative of boarder, national trends. They’re often not.

It’s also easy to present the information which is available as fact when it is, at most, currently indicative. Mr. Hunt’s commentary suggesting that cannabis users face the risk of it being a gateway drug for them is true, of course. There is a possibility that a marijuana user will go on to use harder drugs in the future.

The major point of difference in what is being considered here is the difference between an association and a cause and effect, a distinction that some members of the public may find slight (although it isn’t.)

The evidence in rats (their brains were primed by use of marijuana, alcohol and / or nicotine – see above) shows an association between the use of one drug and the later use of another. It does not prove a causal link, however – that is, the evidence available does not support that the use of cannabis causes the use of other drugs later on.

A number of factors could contribute to muddying the waters around this question. Perhaps some rats (or people) are more susceptible to the effects of drugs – and therefore used both marijuana and later harder drugs. In that case, the marijuana did not cause the harder drugs to be taken.