Cannabis is the in Canada, after alcohol. While there is an in-depth understanding of the , cannabis is a much more complex substance and can affect consumers differently depending on the product type, amount used and a person’s potential tolerance.
This has led to a number of misconceptions about the true impact of cannabis on driving. Research has shown that Canadians perceive driving under the influence of cannabis to be when others engage in such behaviours.
Our (CHERP) research team spoke to over the summer of 2021 to get their perspective. They indicated that driving under the influence of cannabis was normalized behaviour, and because it was not believed to be as risky, there was peer pressure to drive after cannabis use.
In fact, driving under the influence of cannabis can be a very risky behaviour, which is a grave public health concern. It is essential to provide education and promote public awareness.
Driving under the influence of cannabis
A recent study has shown that . Care must be taken to not misinterpret this as cannabis being safe.
A 2012 analysis summarizing nine earlier studies on cannabis and driving showed that . Cannabis-impaired driving was associated with . The reality is that Canadians have been engaging in risky driving behaviours even before cannabis was legal.
A Statistics Canada report showed that in 2019, . This rate was unchanged from the 2018 pre-legalization report.
Another study, conducted by Public Safety Canada in 2017, reported .
Cannabis impairs driving differently than alcohol
, and making the right decisions at the right time can save lives. Cannabis containing affects motor co-ordination and reaction time, can cause hallucination and increases the risk of getting into a collision. Many studies show strong evidence that .
The idea that cannabis is less risky than alcohol may stem from the fact that impairment from cannabis can differ from alcohol. The biggest difference being that with cannabis, consumers are less aware of their .
Alcohol consists of a single chemical that has been well studied for decades. It has a reliable test that measures blood alcohol levels and those blood alcohol levels match to . Cannabis on the other hand consists of several chemicals that lead to varying levels of impairment.
THC is the chemical we know the most about and the one that leads to the from cannabis. However, other less studied chemicals may also impair driving, and we are only at the beginning stages of learning about these effects. There are to detect levels of THC in the blood, but the relationship between those levels and impairment is not as clear as those with alcohol.
Factors that affect impairment
It is difficult to predict the exact effect cannabis will have on a particular individual. Impairment can be based on many factors, including the dose of THC, personal experience with cannabis, individual biology and the route of consumption (for example, inhaling versus edibles).
There are several types of cannabis products on the Canadian market, and each product has a different amount of THC and takes a to reach its full effects. The following outlines typical time to effect and duration of impairment.
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Inhaling (smoking or vaping): Effects start in about 10 minutes and typically last two to four hours (up to 24 hours)
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Edibles: Effects start in about one hour and typically last four to six hours (up to 24 hours)
waiting a minimum of four to six hours after consuming cannabis containing THC. intensifies the level of impairment beyond what a user might expect, .
Safety considerations when driving
Cannabis-impaired driving is very risky. It is difficult to advise exactly how long someone should wait after consuming cannabis before driving. The safest choice is to separate cannabis consumption from driving entirely.
However, there are to avoid this risky situation, including:
- Making sure you have a designated driver,
- Calling a friend or loved one to pick you up,
- Taking public transit,
- Calling a cab or a ride-sharing service, or
- Staying over.
Detection of cannabis-impaired driving
Many young people believe that it is difficult for police to detect and charge drivers who consume cannabis. However, (bloodshot eyes, smell of cannabis, shallow breathing or rapid heart rate) can form a reasonable suspicion for police. In addition, there are (horizontal gaze nystagmus (involuntary eye movements), one-leg stand and walk and turn) that are performed to evaluate impairment.
In Canada, the prohibits driving while impaired. Penalties range from a minimum fine to imprisonment, depending on the severity of the offence. Impaired drivers who cause injury or death can face longer periods of incarceration, including imprisonment for life.
Information for parents
A Health Canada survey showed that . However, only four per cent of teens indicated they had discussed impaired driving with their parents.
It is essential to start a conversation with children and teens about the risks of driving under the influence of cannabis. Our CHERP research team’s and social media ( and ) can provide information and resources. Young people need to be prepared to make long before they are ready to get behind the wheel.
Dina Gaid, post-doctoral position, is funded through a grant from Memorial University of Newfoundland, Canadian Center on Substance Use and Addiction, and Canadian Institutes of Health Research
Jennifer Donnan receives funding from the Canadian Centre for Substance Use and Addiction (CCSA) and the Canadian Institutes for Health Research (CIHR).
Lisa Bishop received funding from the Canadian Centre on Substance Use and Addiction (CCSA) and the Canadian Institutes of Health Research (CIHR)
Maisam Najafizada receives funding from the Canadian Centre for Substance Use and Addiction (CCSA) and the Canadian Institutes for Health Research (CIHR).
Maria Josey and Michael Blackwood do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
