Quirks & Quarks

Cannabis and the brain: the knowns and the big unknowns

There's still a lot we don't know about the effects of cannabis on regular users because research was so difficult during prohibition
The new council in Pickle Lake, Ont., decided to opt out, at least for now, from applying to host a legal cannabis dispensary. (Juan Mabromata/AFP/Getty Images)
Listen11:55

With legalization of cannabis on October 17, Canada is embarking on a large scale social, cultural and — yes —  scientific experiment.

And for researchers like Mark Ware, this experiment is a welcome one — and a long time in coming. 

That's because they'll now be able to ask a lot of interesting and important questions about cannabis they haven't been able to ask before because of the way prohibition tended to obstruct scientific research. 

Dr. Ware experienced the difficulties of researching an illegal drug in his work investigating the effects of cannabis as an associate professor of medicine at McGill University. His expertise led to him being appointed as the vice-chair of the federal task force advising the government on cannabis legalization. Most recently, he's taken a leave of absence from McGill University to work in the industry as Chief Medical Officer for Canopy Growth, a licensed cannabis producer.

"We had to have special licenses from everybody involved in the study from the pharmacist to the nurses, to the patients, myself, my entire team had to have special licenses to be able to handle the product, which takes time, of course."

Cannabis is complex at the best of times

Dr. Ware says cannabis research is an enormously rich field. This is because of the complexity of the drug. There are at least 115 cannabinoids, including the best known like THC and CBD.

But the other part of the complexity is that the human brain, in a sense, runs on cannabinoids. Our brain makes and uses it's own endocannabinoids as signalling molecules. "These are working all the time to control things like mood and memory and appetite," said Ware, "it's an amazing system."

THC is the cannabinoid responsible for the psychoactive effects of cannabis.

"It's a very very fat soluble substance. And when it's inhaled into the body or ingested into the through the stomach, it absorbs at different speeds into the blood and is distributed very fast into fatty tissues, like fat cells around the body, but also the brain, which is very fatty substance. And it there binds to receptors, which are quite specific and unique for these cannabinoid compounds," said Ware.

"So THC coming in from the outside, binds to this, and then that gives rise to a huge range of different effects ... changes in appetite, changes in mood, changes in perception of pain, perception of other stimuli, an enormous range of effects. And it's very hard to predict what those will be in any one given individual. We all seem to respond somewhat differently to the doses of THC."

Big gaps in our understanding

Until now, most of the scientific studies that have been done on the effects of cannabis under prohibition have followed one of two paths: looking at the potential downsides of cannabis or the potential medicinal uses for the drug. That's left a huge gap in our understanding of how cannabis affects regular users. 

According to Ware, one of the biggest unknowns is, "who are recreation cannabis users?" 

Here's what we know, without a doubt, about how it affects us:

  • Adverse outcomes are more pronounced in young users who start heavily and frequently
  • Smoking cannabis causes an irritation to the lungs and even bronchitis
  • Negatively affects short term memory
  • Delays your reaction time

"Once you've actually administered the substance, [it] tends to be associated with impairments in thinking, cognition, memory, ways in which people are processing thought," said Ware. To some, he says, this can lead to people feeling more creative.

It's not that there are likely huge hidden harms associated with cannabis, said Ware. "Certainly tobacco and alcohol have much higher rates of harm in many different perspectives than cannabis does, as far as we know at the moment. So in terms of relative harms, this is a relatively safe drug." 

Ware is most looking forward to digging further into therapeutic uses for cannabis. 

"I think we are a society that struggles with managing chronic pain, managing a wide range of other debilitating problems - spasticity, brain injury problems, we have problems with disorders, and so on. And I'm fascinated by the process of possibility that cannabinoids may be a useful tool in the toolbox pharmacologically of managing these conditions," said Ware. "So for me, the possibility of expanding the cannabinoid toolbox, is tremendous."

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