Only cannabis use at or before work linked with higher work injury risks

July 31, 2023 (Toronto, Ont.)—Are workers who use cannabis at greater risk of having an injury at work? Yes, but only those workers who use cannabis during or before a work shift. Workers who only use cannabis outside of work hours are at no greater risk of getting injured at work than workers who do not use cannabis at all.

That’s according to a study by the Institute for Work & Health (IWH) published today in the Canadian Journal of Public Health (doi:10.17269/s41997-023-00795-0). The study, which is free to read, is the first to distinguish cannabis use during or before a work shift from use outside of work hours when examining its relationship with work injury risk. 

Our study findings demonstrate that it’s important to consider when cannabis use is taking place, says IWH Scientist Dr. Nancy Carnide, lead scientist on the study. Rather than considering any cannabis use as an occupational safety risk, I think employers may need to reframe their approach and focus on use that is likely to lead to impairment at work.

Indeed, the study finds workers who report consuming cannabis during work or before work are twice as likely to get hurt on the job as those who don’t use cannabis. Irrespective of whether a worker’s job is safety-sensitive or not, workplace cannabis use poses a risk to future workplace injury, Carnide’s study shows. 

The study was conducted as part of a research project that began in June 2018, before the legalization of non-medical cannabis in October 2018. The project’s objective was to understand changes in workers’ cannabis use, and their perception of use, before and after legalization. 

This study drew on three waves of surveys completed between the summer of 2018 and the summer of 2020. The sample used in this study included workers who took part in at least two successive survey waves—a total of 1,715 workers.

Employers’ concerns about workplace impairment associated with cannabis use shouldn’t be minimized. Workers should be educated about the workplace safety risks of using cannabis before or during work hours, which we clearly observed, says Carnide. 

However, zero-tolerance workplace policies that prohibit workers from using cannabis entirely are likely too broad. Workplaces could instead consider incorporating minimum wait periods before a work shift when cannabis consumption is not allowed, she adds. 

To request an interview with Dr. Carnide, please contact:

Andrea Larney
Communications Associate
Institute for Work & Health
289-387-0153 (cell)
416-927-2027 ext. 2156 (office)
alarney@iwh.on.ca

Uyen Vu 
Communications Manager
Institute for Work & Health 
613-979-7742 (cell)
uvu@iwh.on.ca