Looking at the science on cannabis, kids and addiction

Last week the Canadian government finally legalized and regulated the production, distribution, and use of cannabis. Like many of my peers, this change in the law didn’t have a serious effect on my life. I didn’t ingest cannabis before legalization and I have no strong desire to do so now. It is not that I have any moral qualms about the stuff, I have just always worked in fields where post-incident drug testing is a reality and knowing my analytical chemistry have been aware that casual use can stay in your system far longer than most recognize. I have also had a lifetime of lung problems and being around people smoking anything leaves me searching for my inhaler. That being said, I have read a lot of misinformation by “cannabis experts” and so wanted to write a brief blog post highlighting some research that some of the activists would prefer you not understand. Specifically, that cannabis can indeed be addictive and it is very much something that you want to keep well away from young people. Let’s start with the second point first.

Cannabis and youth.

I can’t count the number of cannabis activists I have seen in the last few weeks proclaiming that cannabis is harmless and there shouldn’t be any serious limitations on its distribution and use. The simple fact is that cannabis is a psychoactive substance. Put another way, if cannabis was not a psychoactive substance there would be no particular reason why so many people would be interested in using it. As described in a science dictionary, cannabis

affects both the cardiovascular and central nervous systems. The major psychoactive component in marijuana is delta-9-tetrahydrocannabinol, or THC. After entering the bloodstream through blood-gas exchanges associated with smoking, THC combines with receptor sites in the human brain to cause drowsiness, increased appetite, giddiness, hallucinations, and other psychoactive effects.

One thing I was taught early in my study of toxicology is that the brains of adults and those of children react differently to the same compounds. That is why so many medicines that are fine for adults are not recommended for children. Cannabis fits into that class. While cannabis can, quite rightly, be recommended to children by doctors to treat specific maladies, it should be carefully avoided for most youth. The science is clear that cannabis use, and particularly heavy cannabis use:

All this makes it clear that cannabis is not the harmless substance for youth that some of its more ardent proponents claim and strongly supports the government’s decision to limit the use of the substance to adults.

Many activists have pointed to a recent Journal of the American Medical Association (JAMA) study on cannabis and cognition: Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults, A Systematic Review and Meta-analysis. Let’s be clear that study did not deal with depression, schizophrenia or other anxiety disorders, but rather to cognitive function which involves things like reasoning, memory and attention. Moreover, the study didn’t actually say that cannabis was harmless. Rather, the JAMA study concluded:

Associations between cannabis use and cognitive functioning in cross-sectional studies of adolescents and young adults are small and may be of questionable clinical importance for most individuals. Furthermore, abstinence of longer than 72 hours diminishes cognitive deficits associated with cannabis use.

What do they say this means in plain English? That continued cannabis use may be associated with small reductions in your child’s cognitive ability but results suggest the cognitive deficits are substantially diminished with abstinence. Read that last line again carefully. They aren’t saying that kids won’t see a reduction of cognitive ability, only that following abstinence the loss won’t have a clinical effect on your kids. Put in a way parents will understand: if your kid uses cannabis regularly they likely won’t have cognitive deficits they just may lose a few IQ points over the long term. Not exactly a ringing endorsement in my mind.

An article in Scientific American put it best:

Repetitive or high doses of psychoactive drugs like cannabis, alcohol and hallucinogens interfere with the normal development of the brain. Not a good thing, and cause for controls on the access youth can have to substances.

Cannabis and addiction

As for addiction, the research is equally clear, cannabis is not as addictive as many other “drugs of abuse” but “it appears to conform to the general patterns of changes described in the Koob and Volkow model of addiction.  In non-science-speak what this means is that it creates a biochemical change in users’ brains…it is addictive. That is why cannabis use disorder is included in the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5). Biochemically, the neurochemical basis of cannabis addiction is described:

The psychoactive compounds contained in cannabis induce their pharmacological effects by the activation of at least two different receptors, CB1 and CB2 cannabinoid receptors. Multiple studies have demonstrated the specific involvement of CB1 cannabinoid receptors in the addictive properties of cannabinoids. Several neurotransmitter systems involved in the addictive effects of other prototypical drugs of abuse, such as the dopaminergic and the opioid system are also involved in cannabis addiction.

What does this mean for users? Well for most casual adult users there is little need for concern. Cannabis is less addictive than alcohol and a lot less addictive than nicotine or many other “drugs of abuse”. As for it being a “gateway drug” that is also not strongly supported. Rather, the research appears to indicate that those who are predisposed to drug addiction often start with pot rather than pot making you predisposed to other drugs. That being said if you are a heavy daily user of cannabis you can develop a neurochemical dependence, which is the clinical definition of addiction. So when the government says that regular users of cannabis can become addicted, they are neither lying nor are they wrong.


To conclude, cannabis is a psychoactive substance that the research appears to indicate can be enjoyed in private by consenting adults with little long-term harm as long as it is enjoyed in moderation. Like many other psychoactive compounds it causes neurological changes in the brains of users and when used regularly can result in addiction. Moreover, those neurological changes while minor and usually temporary in adults, can have long-term consequences in youth and children. Thus, like alcohol, cannabis use by youth should be avoided except when prescribed by a medical practitioner for a recognized medical condition.

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2 Responses to Looking at the science on cannabis, kids and addiction

  1. paulmackey says:

    Always appreciate your clear and concise reviews. As a Physician who has dipped in and out of the Cannabis Twitter Maelstrom I have found pretty much the same. I have found the pro cannabis crowd to be biased against the downsides, even amongst researchers who should know better and who should be aware of their biases. And there is a dedicated group who are twitter trigger happy and ready to eviscerate anyone who should dare question the blessed weed. My favourite was the (non scientist) dude who claimed that all the “problems” were due to the “other chemicals” in cannabis and his stuff was pure and had no side effects and cured everything. Hard to argue with that eh! I don’t claim to know all there is to know by any stretch but have been attempting to learn a lot. The discussion around schizophrenia is complex. There is reasonable (though not iron clad) argument that cannabis use may “only” be exposing a genetic predisposition and not actually increasing the likelihood of schizophrenia. This appears separate from the propensity of higher potency cannabis preparations to cause isolated episodes of psychosis. Not exactly something you want to find out though.


  2. Chester Draws says:

    It always amuses me that people claim that cannabis doesn’t affect your brain, when the entire purpose of taking it is to affect your brain!

    I’m interested in the “medicinal” cannabis effects. If the wild claims about its ability to treat a variety of afflictions are halfway true, then Canada should see some sustained reductions in admissions and required treatments. I’m picking that they won’t, but it will be interesting to see.

    I’m also picking an increase in road deaths.

    On the plus side, there should be a drop in the crime rate.


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