We wish you a Merry Cannabis!

Nearly 50% of British Columbians have tried cannabis at some point in their lives for a variety of different reasons. As we have highlighted in this latest CARBC blog series, the landscape of cannabis is changing both in Canada and internationally. More evidence is emerging about the potential benefits of cannabis and several US states have begun to legalize and regulate cannabis consumption in a similar way to alcohol. However, cannabis is not risk free and finding the balance between benefit and harm will continue to be an ongoing challenge for researchers, policy makers and cannabis consumers alike.

Over the last seven weeks we have discussed many different facets of cannabis use.  Our guest blogger from the Canadian Drug Policy Coalition (CDPC) demonstrated some of the complexities of changing cannabis regulation in Canada.  The post on changes to the medical marijuana regulations in Canada is a good illustration of some of these complexities and it spoke to the potential benefits and barriers of these changes for those using and producing cannabis for medical purposes.  Despite the challenges of changing cannabis policy, there have still been concerted efforts made by organizations such Sensible BC, who launched a campaign this past fall to gain enough public support to put decriminalization of cannabis to a referendum vote.  The campaign fell short of the required number of signatures so decriminalization of cannabis in BC is off the table for now. However, it will be interesting to watch how the reality of legalization unfolds in places such as Washington State and Colorado, as there are still many hurdles for them to overcome.

The blog series also highlighted the growing body of evidence about the positive applications of cannabis. For example, there is new research showing that cannabis may be an effective and less harmful substitution for other drugs. Further, we heard first-hand about the benefits of using cannabis to manage symptoms of chronic illness. On the other hand, it is important to bear in mind that there are potential risks associated with cannabis use such as the links between cannabis and psychosis and dangers associated with driving under the influence of cannabis. There are, however, ways of mitigating these risks and two of our posts provided some very practical recommendations for how to lower your risk from cannabis use, as well as how to communicate safe practices with young people.

A big thank you to all of our guest bloggers for their fantastic contributions to this latest CARBC blog series and thanks also to our readers for engaging in this topic and for your thoughtful comments and feedback.


Have you ever wondered what the term “Harm Reduction” means and what it looks like in practice? We are excited to announce that the next CARBC blog series starting in January 2014 will feature an amazing line up of guest bloggers who are experts in the field of harm reduction in BC and across Canada.


Driving under the influence of cannabis

Attitudes toward driving under the influence of cannabis vary greatly. Some individuals claim that driving under the influence is extremely dangerous; whereas others suggest that cannabis is a fairly innocuous substance that does not increase your risk of collisions.  Research indicates that the true answer is somewhere between these two extremes. Comparisons between studies of alcohol intoxication and collision risk versus studies of cannabis intoxication and collision risk show that alcohol has more detrimental effects on driving than cannabis has on driving. Conversely, some research has shown that drivers under the influence of high levels of cannabis attempt to compensate for their condition by driving slowly and cautiously. However, while compensation can help reduce the risks of collision, these risks are not fully eliminated.

A recent review of the evidence showed that cannabis doubled the likelihood of a collision, which would be similar to the likelihood of collision from having a blood alcohol content (BAC) of .05%, the legal alcohol limit in most Canadian provinces.  For comparison, heavy alcohol intoxication to a BAC of .20% alcohol is related to over an 80 fold increased likelihood of a collision. Cannabis affects your attention span making it harder to concentrate on driving and makes it difficult to shift attention to deal with changes in the environment. Evidence suggests cannabis may also impair tracking ability (i.e., harder to follow your lane), and sense of time and distance.  The duration of impairment from cannabis lasts on average about 90 minutes, but it is best not to drive within 4 hours after smoking cannabis.

It is a criminal offense to drive under the influence of cannabis, however, nearly half a million Canadians admitted to driving within two hours of using marijuana or hashish in 2006 and youth report driving after cannabis more than after alcohol (40% vs. 20%). If a police officer suspects that you are driving while under the influence of cannabis, you can be sent to the police station for examination of impairment by a drug recognition expert, and possibly be asked to provide a biological specimen, such as urine or blood for analysis. This process is time consuming and cumbersome for the police. Some countries have dealt with the issue by implementing roadside saliva testing – a test that can detect the use of cannabis over the past few days. For example, Australia has a zero tolerance policy for driving under the influence of cannabis and uses roadside saliva tests to assess for the presence of THC. However, saliva and urine tests are not as effective at detecting impairment compared with the Breathalyzer test used for alcohol, where increased blood alcohol concentration corresponds closely with safety risk. That is, a person who tests positive for cannabis on a saliva or urine test may not be under the influence at the time of the test and therefore their driving may not be impaired. Another more accurate option for detecting cannabis impairment is the use of blood tests, currently being used in Germany, however these tests are also more intrusive and difficult to implement at roadside.

Driving under the influence of cannabis is a serious public health concern and with the recent legalization of cannabis in Washington State and Colorado and the continued movement towards decriminalization of cannabis in BC, cannabis related driving policies will be an important component of any regulatory system. 

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Authors: Scott MacDonald, Assistant Director, CARBC, and Chantele Joordens, Research Associate, CARBC


Lowering the Risks of Cannabis Use

As we move toward greater acceptance of cannabis use, and possibly decriminalization or legalization down the road, it is important to recognize cannabis is not a benign drug. While it has benefits, like any other drug, there are also risks involved. Whenever we choose to use cannabis, it is helpful to know what steps we can take to ensure that our use is the least harmful possible. Here are some things to think about to help reduce the risk of harms and bad experiences.

Some of the risks around cannabis are related to its production. Since cannabis is illegal and unregulated, it is often produced in conditions where products are not tested for quality and potency. One way consumers can lessen the risk of experiencing harms is to purchase cannabis from someone who knows about the drugs they sell. Another precaution is to carefully inspect the cannabis for visible contaminants such as molds and mildew. And, since levels of THC (the main psychoactive ingredient in cannabis) can vary, starting with a small amount helps adjust the dosage to achieve the desired effect. Using as little as is necessary also helps prevent inhaling unnecessary smoke and toxins.

The method used to consume cannabis also influences the risk of harmful consequences. Using a vaporizer is safer than smoking, since cannabis smoke contains tar and toxins. But, if smoking cannabis, research suggests joints are safer than bongs or pipes. Bongs filter out more THC than tars since water tends to absorb THC. This requires puffing harder, increasing the amount of tar that is inhaled. If using a bong or a pipe, consumers should avoid those made of materials (such as plastic) that may be toxic when heated. (Bennett, 2008; Gieringer, 1996, Rev. 2000).

Other ways to lessen risks include taking shallow puffs rather than deep inhalations, and if sharing joints or other devices, avoiding touching the lips (this helps decrease the risk of spreading germs and viruses). When eating or drinking cannabis, consuming a small amount and waiting at least one hour to feel the effects before using more helps avoid getting higher than intended.

Making informed decisions about where, and with whom, cannabis is used is another way to reduce adverse consequences. For instance, staying in the company of trusted friends in a safe place helps manage potential uncomfortable effects such as feeling too high or anxious. If going out, it is important to avoid driving. Cannabis can impair motor coordination, judgment and other skills related to safe driving (Mann, et al., 2008; Ramaekers, et al., 2004).

People sometimes mix cannabis with other drugs to experience different effects. But the effects of cannabis are intensified and may last longer than expected or wanted if combined with alcohol or other drugs at the same time. Cannabis in combination with even small doses of alcohol impairs driving ability more than either drug used alone.  And, tobacco contains many cancer-causing toxins, so it’s safer to use cannabis by itself.

All of the above practices are important to keep in mind when choosing to use cannabis. While all drug use involves risk, being clear on safer ways to use the drug helps to minimize harms, both acute and over time.


Author: Bette Reimer, Research Associate at the Centre for Addictions Research of BC

Helping Youth Make Sense of Cannabis

We have all heard a variety of claims about cannabis. Some are scary, like, “cannabis causes psychosis” or “cannabis leads to brain damage and dropping out of school.” Others tell a different story, “cannabis is a miraculous herb that alleviates the symptoms of everything from hiccups to Multiple Sclerosis.”

Making sense of these competing claims can be confusing . While there is at least some truth in almost all of them, accurate and balanced information about cannabis is more complex than simple statements. It is particularly important for young people to realize that there are no simple answers. People are complex beings. Cannabis use can affect  us all differently, but it has potential to impact our minds, bodies, relationships and future prospects.

So where do we begin? We need to acknowledge that all drugs can be both good and bad. Even medications recommended by a doctor can cause harm. Since all drug use carries some risk, it is important to learn how to weigh the potential benefits against the potential risk. Fortunately, human beings have been doing this for a long time. And the wisdom of the ages might be summed up as, “not too much, not too often, and only in safe contexts.” Using more of a drug (or a higher strength preparation) or using daily as opposed to once in a while is more dangerous. But risk is also linked to a wide range of contextual factors. Age – the younger a person is when they start using cannabis regularly, the more likely they are to experience harms in the short term or later in life. But other factors, like where and with whom one uses, also impact risk. Smoking cannabis on school property or driving under the influence are examples of particularly high-risk contexts for quite different reasons.

The reasons why we might use cannabis are also important, and they influence the balance of risk and benefit. If our use is motivated only by curiosity, for example, our use will likely be only occasional or experimental. On the other hand, if our use is about fitting in with a particular group or a way to cope with anxiety or some other mental health problem, we are more likely to develop a more regular and riskier pattern of use. Yet again, if we are consciously choosing to use cannabis to address troubling symptoms related to various health challenges, we may find it relatively easy to manage our use in a way that minimizes risk.

While it may be helpful to know the various potential risks and benefits associated with cannabis use, the more important issue is to become consciously aware of our own pattern of use and our reasons for using or not using. As human beings, we tend to “outsource” control of our behaviour to the environment. For example, when we are with our friends, we may talk a certain way. But when we are talking with our parents, our teachers, our boss – without thinking about it – we slip into a different way of talking. Drug use is more dangerous when we allow it to become a pattern that we don’t think about.



Author: Dan Reist, Assistant Director (Knowledge Exchange) at the Centre for Addictions Research of BC

Cannabis and psychosis: Is there evidence of causal association?

It has been well known since historic times that cannabis may cause a variety of psychiatric symptoms. In fact, the desire to take cannabis or marijuana is primarily to obtain mental effects, and the line may be thin even in an occasional user between experiencing a pleasant and exciting psychoactive effect and a real psychotic episode. “Cannabis psychosis” is a term widely used for psychotic episodes resulting from cannabis use. These occur during or shortly after intake and may last days or weeks, but subside after discontinuation of the drug. They may require hospitalization and medication. Comprehensive summaries of mental health effects of cannabis have been published by Murray and Hall & Degenhardt.

It has often been debated whether use of cannabis can cause long-term psychotic states, and in particular schizophrenia and other chronic psychoses. Seeing patients with a combination of heavy cannabis use and schizophrenia, I was intrigued to assess the causal direction of the association. It was in the 1980s when I found out there was a survey on drug use in a national cohort of 50,000 Swedish 18-19 year old male conscripts (one year of military service was compulsory in Sweden until 2010) that we could link to data on occurrence of schizophrenia later in life. We found that those who reported use of cannabis in adolescence had a doubled risk of schizophrenia compared to those who did not use cannabis. With data on social background, psychological characteristics, and psychiatric condition assessed at conscription, we could control for such factors that might influence the association.

We have continued to follow this cohort and the men are now over 50 years old. The contribution of cannabis to new cases of schizophrenia has declined in occasional users but those who reported heavy use of cannabis in adolescence still have a twofold increased risk of schizophrenia, even at older ages. We do not know whether this is due to continued use of cannabis, or whether heavy early use could indeed have had very long lasting effects.

In recent years, several other studies have also found an association between cannabis use and later onset of chronic psychosis. A review was published in 2007 concluding that there is now “sufficient evidence to warn young people that using cannabis could increase the risk of developing a psychotic illness later in life.” The paper was accompanied by an editorial in which the prestigious journal the Lancet admitted that they had previously underestimated the risk of harmful effects of cannabis.

We recently studied the pattern of care of the patients with schizophrenia in our cohort of male conscripts, and it turns out that those patients with a history of cannabis use had double the number of total days in hospital and around double the number of hospitalizations that were twice as long in duration of those who did not have a history of cannabis use.

Thus, there is now evidence that cannabis is indeed a contributory cause of chronic psychoses, including schizophrenia. Certainly, cannabis is not the only cause of chronic psychosis. There generally needs to be other factors, such as genetic factors, personality characteristics, etc. to cause schizophrenia or other long-standing psychoses. It has been shown that the risk of psychosis in cannabis users is especially strong in psychologically vulnerable persons. Thus young people, and especially persons with mental health illness, should be warned about the risk of chronic psychotic disorders as an effect of cannabis use. Not only because of the risk of chronic psychosis, but also a number of other negative physical and mental side effects.

*Please note that the material presented here does not necessarily imply endorsement or agreement by individuals at the Centre for Addictions Research of BC


Peter Allebeck, Professor of Social Medicine, Karolinska Institute, Stockholm, Sweden



Cannabis: the Exit Drug

Cannabis is neither completely harmless, nor is it a cure-all, but with polls showing that Canadians overwhelmingly support cannabis policy reform, it’s fair to assume that most people no longer believe that legalization would lead to the end of the world.  Yet, some who support reform nonetheless have concerns that adding yet another legal drug (alongside alcohol, tobacco and pharmaceuticals) for society to struggle with might result in an increase in use.

But what if the legalization of adult access to cannabis also resulted in a reduction in the use of alcohol and other drugs?  What if rather than being a gateway drug, cannabis actually proved to be an exit drug from problematic substance use? A growing body of research on a theory called cannabis substitution effect suggests just that.

In a nutshell, substitution effect is an economic theory that suggests that variations in the availability of one product may affect the use of another.  Perhaps the best example of deliberate drug substitution is the common prescription use of methadone as a substitute for heroin, or e-cigarettes or nicotine patches rather than tobacco smoking.

However, substitution effect can be also be the unintended result of public policy shifts or other social changes, such as changes in the cost, legal status or availability of a substance.  For example, in 13 U.S. states that decriminalized the personal recreational use of cannabis in the 1970s, research found that users shifted from using harder drugs to marijuana after its legal risks were decreased (Model, 1993).

Findings from Australia’s 2001 National Drug Strategy Household Survey specifically identify cannabis substitution effect, indicating 56.6% of people who used heroin substituted cannabis when their substance of choice was unavailable.  The survey also found that 31.8% of people who use pharmaceutical analgesics for nonmedical purposes reported using cannabis when painkillers weren’t available (Aharonovich et al., 2002).

Additionally, a 2011 survey of 404 medical cannabis patients in Canada that colleagues and I conducted found that over 75% of respondents reported they substitute cannabis for another substance, with over 67% using cannabis as a substitute for prescription drugs, 41% as a substitute for alcohol, and 36% as a substitute for illicit substances (Lucas et al., 2012).

This and other evidence that cannabis can be a substitute for pharmaceutical opiates, alcohol and other drugs – and thereby reduce alcohol-related automobile accidents, violence and property crime, as well as disease transmission associated with injection drug use – could inform an evidence-based, public health-centered drug policy. Given the potential to decrease personal suffering and the social costs associated with addiction, further research on cannabis substitution effect appears to be justified on both economic and ethical grounds.

Maximizing the public health benefits of cannabis substitution effect could require the legalization of adult cannabis use, as currently being implemented in Colorado and Washington State. So the question is: do we have the courage to abandon long-standing drug policies based on fear, prejudice and misinformation, and instead develop strategies informed by science, reason and compassion?


*Please note that the material presented here does not necessarily imply endorsement or agreement by individuals at the Centre for Addictions Research of BC


Philippe Lucas is a Graduate Researcher with the Centre for Addictions Research of BC, President of the Multidisciplinary Association of Psychedelic Studies Canada, and a founding Board member of the Canadian Drug Policy Coalition. In 2012 he was awarded the Queen Elizabeth II Diamond Jubilee Medal for his work on medical cannabis.


Marijuana, a Friend to Crohn’s Patients Everywhere

I am 33 years old, married, a university graduate, and a business professional. I also have Crohn’s Disease, and I have used marijuana to treat ongoing symptoms such as pain, nausea, lack of appetite, and low energy. I do not use “medical” marijuana, but rather the dispensaries that currently fall under a grey area of legality in BC. I take no other pharmaceuticals for my Crohn’s Disease, and am able to control it with diet and a healthy lifestyle. I have chosen to write this blog as anonymous because unfortunately, there is still a fair amount of stigma, stereotypes and misinformation surrounding the “typical” marijuana user (and I think my parents would kill me).

I started using marijuana as part of my treatment when I was 26. My doctor informed me I was underweight and needed to gain about 15 lbs. The problem was, I couldn’t eat. My stomach would turn at the thought of eating, and I would often throw up after meals. I started smoking a very minuscule amount of weed before dinner so that I could not only eat, but enjoy eating again.  It worked like a charm.

However, I struggled to find a reliable source of marijuana. I did not like the idea of going to a dealer. It was shady and illegal and I was never quite comfortable with it (though it was never very difficult to come by). My GP at the time was not open to prescribing medical marijuana to me, and I felt extremely judged! She was very closed minded about the medical benefits of marijuana despite the living proof standing right in front of her, 15 lbs heavier and healthier than before.  

In 2011, a friend took me to a medical marijuana dispensary in downtown Victoria. She was a member there due to ongoing and severe debilitating back pain, which would put her on the floor for days at a time. To become a member at the dispensary, I simply needed proof of my condition and photo ID. Crohn’s is classified as Category 2 symptom on the Health Canada info page on medical marijuana. I brought in proof of my condition, sat through a 45-minute orientation and happily became a full-fledged member of the Victoria Cannabis Buyers Club. The role of the dispensary is to serve those who have legitimate conditions that can be treated by marijuana, but whose doctors will not prescribe it. They offer an incredible selection of products, including dried smokeables, edibles, oils, creams, compresses, and capsules. I tend to favour their Cannoil, which is made specifically to treat upper gastrointestinal disorders, and has provided me relief from not only nausea, but also severe cramping and bouts of diarrhea. The staff is friendly and knowledgeable on recommending the different strains to best suit your specific needs. As for the clientele, you’d perhaps be surprised to know that more often than not, it’s other “normal” people, business professionals, moms and grandparents seeking relief from what ails them.

Will I seek eligibility for medical marijuana? Perhaps one day, though I feel less inclined to now. I am a light user, and I like the convenience and selection of products that are on offer at the dispensary. I will probably also start growing my own, when I have suitable space to do so, so that I may control exactly what is in my medicine.

Though currently not using, marijuana will always be a part of my wider treatment plan. It’s enabled me to avoid harsh pharmaceuticals that are, in my opinion, far worse for me than something that has been grown naturally from the earth.

Further information on Crohn’s and Marijuana can be found here:

Treatment of Crohn’s Disease with Cannabis: An Observational Study

Cannabis Alleviates Symptoms of Crohn’s Disease

Medical Marijuana for Crohn’s Disease

Medical Marijuan & Crohn’s Disease—Getting your Doctor to Sign Health Canada’s Paperwork

*Please note that the material presented here does not necessarily imply endorsement or agreement by individuals at the Centre for Addictions Research of BC


Author: Anony Mous