The arguments for and against allowing medicinal use of cannabis

by Marc Wilson / 23 September, 2018
Photo/Getty Images

Photo/Getty Images

RelatedArticlesModule - Medicinal cannabis

There’s an increasing amount of evidence on cannabis effects, but it's far from straightforward.

In 2016, after a US conference, I stopped off in Santa Monica and stayed near Venice Beach. This famous strip of California sand is defined by the combined smells of cannabis and urine, according to a reviewer on Google Maps.

The place has a significant homeless community and no small number of not-homeless semi-drunk urinators. There are also several “Green Doctors” practices – green-coated people who dole out cannabis. For medicinal use, of course.

Kiwis are having a discussion about that very question: whether and how to allow cannabis for medicinal use. One part of the debate might be said to be shaped by the Reefer Madness stereotype – the 1930s anti-weed propaganda film. Another is defined by accounts of first-hand experience that sometimes looks a lot like the film’s stereotype. Then there are the equally poignant stories of people who might be helped, perhaps dramatically, by easier access to medicinal cannabis.

So, what do we know? I did what I usually advise my students embarking on a research project to do – find the most recent, high-quality review of the research. In this case, the first one that Google found for me was “The Health Effects of Cannabis and Cannabinoids”, a comprehensive 2017 review of research (taking into account the quality of that research) prepared by a committee of the American National Academies of Sciences, Engineering and Medicine. That’s a lot of words. Must be good.

Cannabis, the research has identified, contains more than 100 chemical constituents, or cannabinoids, that act on a family of brain receptors to produce the effects society has come to know and feel ambivalent about. Primary among cannabinoids is tetrahydrocannabinol, or THC, which appears to be the main culprit for weed-induced intoxication. Not only are our cannabinoid brain receptors involved in this process, but also things like memory, motor control and appetite. Hence the munchies.

The researchers say there is “conclusive” evidence that cannabinoids are effective for treating adult chronic pain, nausea and vomiting caused by chemotherapy, and lessen some of the physical symptoms self-reported by people with multiple sclerosis. There’s “substantial” evidence for improving sleep among people with a variety of medical complaints, notably those involving various kinds of pain. On the mental-health front, there is “limited” evidence of improvement for people experiencing Tourette’s, anxiety, dementia and post-traumatic stress disorder.

For these people, there appears to be a good argument for taking the medicinal-use debate seriously. The review, however, doesn’t just look at positive outcomes.

If you’ve ever seen a US-style pharmaceutical advert, you’ll know that the list of side effects can be longer than the list of benefits, and the same applies here. “Substantial” evidence supports concern over respiratory symptoms among chronic users, motor vehicle crash risk and lower birthweight of offspring. There’s also “moderate” evidence for “impairment in the cognitive domains of learning, memory, and attention” among acute users. Or to put it another way – behaving like a stoner.

One of the greatest concerns is the substantial evidence for development of schizophrenia and other psychotic disorders. There’s also a dose-response effect – greater frequency of cannabis use tracks greater risk. For obvious reasons, the researchers note that we have relatively fewer studies looking at pregnant women and adolescents, but the risks are greater for both.

As a fan of evidence-based practice, I’m pleased that there’s an increasing amount of evidence on cannabis effects. But I don’t see this as being a straightforward discussion.

This article was first published in the September 22, 2018 issue of the New Zealand Listener.

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