Quirks & Quarks

Addiction and cannabis: it's real and this is what you need to know about it

A user's propensity to becoming addicted varies according to their genetics, age, and personal history
Weed has been legal in Canada for one year. (Darryl Dyck/The Canadian Press)

Since the days when we feared "Reefer Madness," attitudes about cannabis have changed enormously. And this is particularly true about addiction. Most people, certainly most cannabis users, would probably suggest that cannabis isn't addictive. 

This may be true for most people, but the best research indicates it's it's not true for everyone. Now scientists are starting to hone in on who's most vulnerable and why adolescents or teenagers should probably avoid it.

"The currently bandied about statistics suggest that of regular cannabis users, about 10 percent meet criteria of Cannabis Use Dependence, which means that they spend a lot of time thinking about it, they spend a lot of their time trying to get it, and it may affect adversely their social and work functions and so on," says Mark Ware, a scientist who's studied cannabis as a professor of medicine at McGill University, but is now the Chief Medical Officer for the licensed producer Canopy Growth. 

People with cannabis use disorder often start using as a way to relax. But as their use increases in frequency, they often find their relationship to cannabis starts to change.

"You know, if you have a bad day, or if you're stressed out by your relationships, or you know any number of things in your life, it's really easy to use pot to just kind of forget all that," said a 38 year old father and government employee from Victoria whose name we've agreed to withhold.

"I've always had a busy mind. And I remember finding it hard to wind down in the evenings. And soon as I smoked a joint, you know a everything was fine. Food tasted better. Movies were funnier."

But after smoking daily for 20 years, his feelings about his cannabis use changed.

"Instead of actually smoking pot reducing the anxiety, in the end it actually created the anxiety. I would have a hard time communicating with people. You know I didn't want to look people in the eyes, didn't really have the right thing to say. And instead of using the marijuana to combat that, in fact, it had turned on me, and it started causing those effects in me."

THC affects our brain's reward system

"I often hear that marijuana is considered to be not addictive," said Jeffrey Edwards, a professor at Brigham Young University in Utah in the department of physiology and developmental biology. "And I think that the best way to think about it is that it might be less addictive than other drugs of abuse."

Cannabis, like many other recreational drugs, from cocaine, to opioids, to alcohol, and tobacco, acts on our brain's dopamine reward system. Edwards say their mechanisms might be slightly different, but the end goal is they all increase the neurotransmitter — dopamine's — release.

According to Edwards, THC — the psychoactive compound in cannabis — and alcohol are probably fairly comparable in the amount of dopamine that they induce, but it's a smaller effect in comparison to drugs like cocaine or methamphetamine.

He studied the effects of cannabis addiction on rodents, so he could look at their brain tissue. When Edwards injected the rodents a single time with THC, there were no permanent changes to the synapses in the reward centre of the brain. 

"But if we did chronic injections where we injected for seven to 10 days consecutively and then we looked at and recorded activity, we found that the synapses were now changed."

Who's most at risk for developing a cannabis addiction

This study was done on adolescent age rodents, which is important because according to Edwards, if you look at the negative impact of marijuana, it's almost always associated with adolescence.

"While both adolescents and adults can can develop cannabis use disorder, adults tend to not have more of these negative long term outcomes that adolescents do," said Edwards.

"With adolescents, it's a little scary because they have an increased chance of abusing other drugs. They can decrease their IQ with chronic marijuana use by an average of about six points. There's increased anxiety and depression, memory loss and other neurocognitive damage that can occur in adolescence. We don't tend to see the same types of detriment in adults as we do in adolescence."

The CB1 receptor that THC binds to in the brain is developmentally regulated, so it changes as the brain is developing until a person reaches their mid 20s. That may be the reason that if a person starts using cannabis when they're an adolescent or teenager, they are at a greater risk of developing a cannabis addiction. But even then, not everyone who tries cannabis at a young age will go on to become addicted. 

Students at L.A. Matheson Secondary School in Surrey, B.C. say despite the health risks and the fact that it is illegal for minors, vaping is rampant among teens. (Steven Senne/Associated Press)

"I think this is a really fruitful area of research where there's people now that are looking at the genetics of individuals to see, is there a propensity for somebody to become addicted to marijuana or other types of of drugs - alcohol even. And so people right now have found that there are certain genetic combinations that tend to increase your propensity."

Until the science catches up and we can tell exactly who's at risk of developing an unhealthy dependence, Ware says people need to be aware of their own family and personal history that could make them more susceptible to addiction.


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