Cannabis, the most widely used illicit drug in the world, and is now legally available in Canada at a store near you. Cannabis is not only readily available but stronger than it was in the past. The concentration of THC, the cannabinoid which results in psychoactive impairment is on average over 4 times greater in marijuana today than it was in the 1980’s. With medical cannabis use increasing over 140% between 2015 and 2016 in Canada and recreational use now permissible by law, individuals who consume cannabis are and will continue to be a part of our society including our workplaces.

Cannabis, the most widely used illicit drug in the world, and is now legally available in Canada at a store near you. Cannabis is not only readily available but stronger than it was in the past. The concentration of THC, the cannabinoid which results in psychoactive impairment is on average over 4 times greater in marijuana today than it was in the 1980’s. With medical cannabis use increasing over 140% between 2015 and 2016 in Canada and recreational use now permissible by law, individuals who consume cannabis are and will continue to be a part of our society including our workplaces.

There is considerable confusion on the impact of cannabis in the workplace and its effect on safe work performance. Information on impairment at the workplace is scarce at best. This is due to the complex nature of cannabis including the concentration of various cannabinoids, challenges determining dose, personal tolerance and frequency of use. Questions around how work performance, vigilance and safety are impacted by cannabis are poorly understood in particular in safety sensitive work environments leaving many employers confused as to how to approach impairment. The simple reason for the lack of empirical data regarding cannabis impairment is that it was, until recently, illegal. As a result, most safety sensitive work environments enforced a zero-tolerance policy and it was irrelevant to understand the potential impacts of cannabis in the first place.

Canadian employers are now faced with new challenges around protecting their workforce from impairment while respecting human rights and privacy concerns. They have been left piecing together the facts and applying what is known, if anything, regarding the potential impact of cannabis use on their work environments.

So what do we know about cannabis impairment and safety? We do know that cannabis consumption results in a variety of physical and cognitive effects that include euphoria, sedation, loss of coordination, anxiety, altered perception of time and space and loss of memory. The challenge is that these effects vary from person to person, strain of cannabis to strain of cannabis, and are governed by several difficult to quantify variables including environment and personality. As a result, it is difficult to quantify the exact effect it will have on our workers.

Very little is understood regarding safety sensitive task performance of different occupations, however the operation of a motor vehicle after consuming cannabis has been the focus of several studies and may be our best means of understanding cannabis impairment. The majority of this research (including large meta-analysis which have combined results to give greater statistical power) have concluded that consuming cannabis produces increases in risk taking behaviour and impacts cognitive and physical performance in a dose response manner (i.e. the “higher” the person is the greater the impairment). It has been long accepted that skills such as tracking, motor coordination, visual functions, and particularly complex tasks that require divided attention are most likely to be impacted by cannabis (Berghaus 1995). If we use the skill of driving as a reference point, it could be assumed that cannabis consumption may lead to impairment in other safety sensitive tasks and pose risk for workers who are acutely impacted by the drug.

Although impairment resulting from cannabis consumption is widely acknowledged, data shows that individuals drive while under the influence of cannabis at a shockingly high rate. A study by Alvarez et al. determined that ~10% of cannabis smokers haven driven while high and do so, not once, but an average of 8+ times in per year (Alvarez 2007). Of even greater concern is that 50% of individuals who are undergoing cannabis treatment for dependency or addiction report driving high at least once in the previous year (Albery 2000). This disregard for the impairment of cannabis, even when broadly accepted as causing a variety of physical and mental effects, poses a challenge for employers who may face complacency in the adherence to policies aimed to protect against the impairment resulting from of the or restriction of cannabis consumption in the workplace.

Complex tasks in safety sensitive environments typically result in the greatest degree of job planning, preparation and training in an attempt to mitigate risk of injury or incident. Not surprisingly, complex tasks requiring multiple cognitive and motor skills are particularly sensitive to cannabis’s impairing effects and display less tolerance than other less complex tasks (Ramaekers 2009). These included activities such as navigating virtual mazes which resulted in higher incidence of wall collisions in those under the influence of cannabis than those consuming a placebo (Ramaekers 2009). Whether this can translate to work environments is inconclusive however poses interesting challenges for employers dealing with impaired workers. How long impairment lasts is still up for debate and will evolve over time as more research is conducted on cannabis and task performance. What is known is that driving within 1 hour after smoking cannabis produced higher odds of motor vehicle accidents than driving within 2 hours (Sewell 2009). Many believe impairments can last up to 24 hours, depending on dose and on the individual, with potential effects lasting up to as long as a week however, the evidence is inconclusive at this point.

So, what does this mean for Canadian employers? What we know is that cannabis use is increasing in Canada and that its recent legalization will result in a continued increase in those using it. The combination of cannabis being readily available in most communities, a tendency for it to be inexpensive, coupled with an increased acceptance by the general public and decreased barrier of entry for younger individuals, employers will almost certainly be one of the audiences most likely to feel the side effects of cannabis use in our country. Those companies focusing on worker education of cannabis, the design and implementation of well-developed drug policies as well as an eagerness to determine the impact of cannabis on safety with academic and medical partners, will be those that are best equipped to tackle the inevitable challenges that will arise from the legalization of cannabis in safety sensitive environments.

Still have questions about cannabis and workplace safety? 

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