risk – Page 2 – Matters of Substance

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.

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

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

Tag: risk

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