Workers who use marijuana off the clock are no more likely to experience workplace injuries compared to those who don’t consume cannabis at all, according to a new study that challenges “overly broad” zero-tolerance employment policies.
However, people who indulge doing work hours are nearly twice as likely to be involved in a workplace incident than non-users and off-duty users, researchers at the University of Toronto, University at Buffalo and Toronto Rehabilitation Institute found.
The study, published in the Canadian Journal of Public Health on Monday, followed 2,745 Canadian workers in safety-sensitive and non-safety-sensitive positions over two years, analyzing the 11.3 percent of those in the sample who experienced a workplace injury during that time period.
“Compared to no past-year cannabis use, there was no difference in workplace injury risk for non-workplace cannabis use.”
The researchers found that among all respondents, 10.2 percent of those who were hurt on the job fell into the non-user category, 11.14 percent were classified as off-duty consumers and 20.13 percent reported using marijuana either two hours before or during work.
“Compared to no past-year use, the risk of experiencing a workplace injury was 1.97 times higher among workers reporting workplace use,” the study says. “No statistically elevated association was seen for non-workplace use.”
“Results of this novel study suggest workplace cannabis use, not use outside of work, is a risk factor for workplace injuries,” the authors concluded.
When stratified for safety-sensitive workers, the rates of injury were 20.14 percent for non-users, 23.3 percent for off-duty consumers and 31.35 percent for those who indulged on the job. For non-safety-sensitive jobs, it was 4.27 percent for non-users, 4.19 percent for off-duty users and 12.3 percent for those who consumed marijuana while working.
The study’s results “bring greater clarity to the question of whether cannabis use increases the risk of experiencing a workplace injury, an issue that the conflicting findings of previous studies have hampered,” the authors said, explaining how prior research has been limited by a failure to account for the timing of consumption in relation to workplace injuries.
“Findings suggest that, when thinking about the potential occupational safety impacts of a worker’s cannabis use, it is important to consider when that use is taking place,” it says. “More specifically, only use in close temporal proximity to work appears to be a risk factor for workplace injuries, not use away from work.”
“No statistically elevated relationship existed between non-workplace use and workplace injury.”
Regardless of whether a job is safety-sensitive or not, the scientists concluded that “only workplace cannabis use poses a risk to future workplace injury.”
“The findings also do not diminish employers’ legitimate concerns regarding workplace impairment. Nonetheless, zero-tolerance policies that prohibit cannabis use entirely, including use outside of work, may be overly broad and are incompatible with the results of this study,” it continues. “In an increasingly legalized environment, more nuanced approaches to workplace policies around cannabis use may be warranted, and could include employing minimum waiting periods after cannabis consumption when impairment is most likely present.”
Relatedly, a 2021 study published by the National Bureau of Economic Research found that legalizing marijuana for adult use is associated with an increase in workforce productivity and decrease in workplace injuries.
Another study from 2019 shows that legalizing medical cannabis was linked to fewer workers’ compensation claims that were less costly on average.