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