Is Marijuana A Gateway Drug?

For quite some time, marijuana was seen as the start of trouble, but why?

Posted Jul 24, 2018

Let me ask you a simple question. Do you believe marijuana use is harmful?

You may say “no, marijuana is a 'soft' drug and doesn’t do any harm.” Or, perhaps you say “yes, because people who use marijuana can get addicted to it or go on to use harder, more dangerous drugs.” Or maybe you’re not really sure because you don’t know much about cannabis and its effects (where have you been exactly?).

In a very real way, your answer depends on your response to the question this article poses - Is marijuana a gateway drug?

Well let me tell you that the experts are divided as well. There is a lot of debate about whether marijuana is actually a harmful drug and whether it does act as a gateway to more "hard" drugs like cocaine, heroin and more. And with 2.6 million new users of cannabis in the United States in 2016, it’s a debate that’s worth getting to the bottom of.

This is especially true as the medicinal qualities of marijuana and THC are explored. Marijuana’s use as a pain relief drug has been touted for decades and its potential use as a substitute for opioids has been discussed recently, especially in light of the incredible increase in the rate of opioid prescription and overdose deaths.

A recent research article (citation below, link HERE) sought to examine whether the use of marijuana really produced reductions in opioid use. It used a large dataset (good) from a well established national survey (ok) that was conducted between 2001 and 2005 (bad) to answer this question. The overall results suggested that marijuana use actually significantly and substantially increased the odds that a person would misuse opioid medication after using marijuana.

This large study, published in a respected psychiatric journal, was used in some recent articles (like THIS one) to remind us of the gateway theory of marijuana use, which I think deserves some more thought.

What is the Gateway Drug Theory?

The Gateway drug theory suggests that marijuana is likely to be used before advancing to ‘harder’ drugs such as opioids.

There are two proposed reasons for this:

1.     Experimentation: Trying a drug like marijuana increases the taste (and perceived pleasure) for other drugs, leading to further experimentation.

2.     Social groups: When a person using marijuana associates with other people who use marijuana, then it is likely they will become exposed to other drugs and substances too. This means there’s an increased opportunity and access to ‘heavier’ substances.

The Gateway drug theory is based on the idea that people who use substances progress through a linear sequence of stages beginning with socially acceptable and legal substances (alcohol, nicotine), followed by the use of illegal soft drugs (cannabis) and later harder illicit drugs (heroin). However, research has challenged this theory with a high percentage (more than 20%) of individuals not following this sequence of steps.

In the earlier mentioned article, marijuana users were 5 to 9 times as likely to experience and opioid problem 3 years later if they used marijuana occasionally, frequently or very frequently respectively. Mind you, the absolute probability for opioid problems was low even for very frequent marijuana users (around 4.5%) but compared to the 0.5% probability in those who didn't use marijuana at all, it was a relatively large jump (see here for a deeper dive into why this is important). So, depending on how you look at it, the increase was incredibly large or pretty small... And even among the heaviest marijuana users, approximately 95% did not seem to have opioid-related issues.

But when it comes to the gateway aspect of the argument, there was more to be examined. That's because substance use can depend on contextual factors such as:

-        Neighborhood and community environment

-        Level of parental supervision

-        Unique characteristics of the individual including their biology and life experience

When it comes to marijuana use in particular, there are some unique aspects to be considered as well:

-        Initial experience with cannabis (whether it is rated as enjoyable)

-        Perception of marijuana as a “safe” or “harmful” drug

What these studies seem to have in common, is the inability to draw a strong causal conclusion about risk factors and later drug use.

What are the shortcomings of Gateway Drug Theory?

The gateway theory of marijuana, and this recent article supporting it, ignore a very important factor, which is that buying marijuana currently involves (in the states that don’t have recreational or medicinal laws) interacting with black market drug sources otherwise known as drug dealers.

This means that, once you buy marijuana you are already breaking the law, and we know that individuals who become willing to commit illegal acts at one point in time are more likely to commit additional illegal acts. In this way, it could be said that its marijuana’s legal status, not its chemical interactions with the brain at all, that is the gateway. Not only that, but once the law is broken and you’ve bought weed from a drug dealer, you can now interact with people who will have access to other illicit drugs. That makes it more likely that you will break the law again and that you will go on to try other substances, because they are now available.

Neither of these would be true if the drug is legal and regulated. I believe this is the reason why most people who try alcohol don’t try illegal drugs, because they work within different regulatory systems. Alcohol is both legal and socially acceptable, and yet can have just as damaging physical and psychological effects as marijuana and other illicit drugs (if not more so). But most people choose to stay on the side of socially acceptable and legal drug use as opposed to crossing over to harder, illicit substances.

All of these things were substantially more relevant in 2001-2005, when only 9 states had approved medical marijuana laws and access was heavily restricted and regulated in many of those. This means that, for the purposes of this study, nearly everyone who admitted to using cannabis was likely also admitting to breaking the law. The biases present back then, many of which are no longer true, mean that the conclusions are somewhat questionable. It would have at least been nice to have seen some mention of state-based analyses that looked at marijuana’s legal status as relevant.

As marijuana becomes legal in essentially all states for medical use and is accepted in more and more states recreationally, it is entirely possible that this whole Gateway theory will simply no longer be relevant. Getting cannabis will no longer involve illegal action, meaning most marijuana users will not have broken the law. I believe this single change will prove to be incredibly important for use of “harder” drugs. No doubt, the next substance in line will now become the “gateway” as its use will be the entryway into the black market of drugs.

Now, to be clear, just because marijuana may not serve as the gateway to the use of other drugs, does NOT mean that it is a completely harmless substance (what is?). I’ve treated dozens of individuals who struggle primarily with marijuana use and marijuana has been shown to have other potential problems…

How is marijuana potentially harmful?

Marijuana has potentially harmful effects in the short-term and long-term on physical and mental health.

Marijuana’s Potential Negative Short-term effects:

While intoxicated by marijuana, the following effects can be observed in users:

-        Memory consolidation difficulties

-        Anxiety, paranoia and panic attacks

-        Increased probability of psychotic symptoms

-        Hallucinations

-        Decreased reaction time

-        Increased risk of heart attack and stroke

-        Coordination problems (impairs driving)

-        Sexual dysfunction (mostly for males)

Marijuana’s Potential Negative Long-term effects:

Repeated use of cannabis over a longer period has been associated with longer-term problems that may include:

-        Lower IQ (especially when use starts early)

-        Poor school or work performance

-        Impaired ability to perform complex tasks

-        Lower life satisfaction

-        Relationship problems

-        Antisocial behavior (stealing money, lying)

-        Financial difficulties and unemployment

-        Addiction

The verdict

On the one hand, research does support the positive effects of cannabis in treating chronic pain conditions (while not as strong a relief in the short-term for many, the probability of developing hypersensitivity to pain seems to be reduced with THC when compared to opioids).

On the other hand, the research on the potentially harmful physical and psychological effects of cannabis use is hard to ignore. Marijuana is damaging to the developing adolescent brain, and it can lead to Cannabis Use Disorder (or addiction).

However, the causal link between cannabis and ‘harder' illicit drug use is still unclear and relies on many other factors such as life experiences, parental supervision, and the social environment and laws.  The gateway theory of marijuana fails to explore the legal implications of purchasing and using marijuana in states where it is still a criminal offence and how this can be the precursor for choosing to use harder, illicit substances.  

All in all, the Gateway Drug Theory of Marijuana has several weak spots and in light of its decriminalization in most states of the United States, it may be even completely irrelavant. 

In this current social and political climate, further research is needed to examine cannabis use as a gateway to further drug use. There is little doubt that, with the rapid increase in opiate related deaths, we want to make sure not to make a problem worse, if possible. And as with any emerging drug research we need to think more critically about the findings put forward.

If you are struggling with marijuana use, or opiate use, and are looking for options be sure to check out SAMHSA's treatment locator here or IGNTD Recovery for some immediately available online help. Or check out The Abstinence Myth book for a different way to look at addiction altogether.


  1. Olfson, M., Wall, M. M., Liu, S. M., & Blanco, C. (2017). Cannabis use and risk of prescription opioid use disorder in the United States. American Journal of Psychiatry, 175(1), 47-53.
  2. For Opioid Use Disorder, Does Cannabis Produce Harm or Reduce Harm?
  4. NIDA Gateway Report
  5. Drug War Facts