Off-the-Job Cannabis Use Was Not Linked to Higher Workplace Injury Risk in Canadian Study

A longitudinal study of Canadian workers found no statistically significant increase in workplace injury risk among people who used cannabis away from work. The elevated risk appeared among workers who reported using cannabis during a shift or within two hours before work—use that may place impairment closer to the time when job duties are being performed.

The study published in the Canadian Journal of Public Health analyzed survey data from 2,745 workers who participated in at least two annual surveys between 2018 and 2020. The sample included people in both safety-sensitive and non-safety-sensitive jobs. Researchers compared workers who reported no cannabis use in the previous year with those who used cannabis outside work and those who used it before or during work.

Overall, 11.3% of participants reported a workplace injury during the study period. After adjusting for personal and work-related factors, the estimated risk was 10.22% among workers with no past-year cannabis use, 11.14% among those who used cannabis only outside work, and 20.13% among those who reported workplace use.

Compared with non-users, workers who used cannabis only away from work had no statistically significant difference in injury risk. Their adjusted risk ratio was 1.09, with a 95% confidence interval of 0.83 to 1.44. By contrast, workers who reported using cannabis during work or within two hours beforehand had an adjusted risk ratio of 1.97, meaning their estimated risk was nearly twice that of non-users.

The pattern was similar across job types, although the estimates differed. In safety-sensitive positions, the adjusted injury risks were 20.14% for non-users, 23.30% for off-duty users and 31.15% for workers who used cannabis at or before work. In non-safety-sensitive positions, the corresponding figures were 4.27%, 4.19% and 12.30%.

The researchers describe the findings as evidence that the timing of cannabis use matters when assessing occupational safety. Earlier studies often measured whether someone had used cannabis in the past year without determining whether consumption occurred close to working hours. By examining use before or during work separately from off-duty use, this study was better positioned to evaluate whether use was temporally related to a later workplace injury.

However, the results do not establish that off-duty cannabis use is harmless or that it cannot affect job performance. The study was observational, relied on participants’ reports of cannabis use and injuries, and did not directly measure impairment at the time of work. It also examined broad categories of use rather than factors such as dose, product potency, method of consumption or individual tolerance.

The findings therefore do not eliminate employers’ responsibility to address impairment—particularly in jobs involving vehicles, machinery, heights, hazardous materials or responsibility for public safety. Canadian federal workplace guidance advises employers and employees to focus on preventing impairment-related hazards while also accounting for medical needs and accommodation obligations.

In practical terms, the study supports a distinction between cannabis use and cannabis impairment at work. Policies that treat any past cannabis use as equivalent to being impaired on the job may be broader than the evidence supports, while rules addressing consumption during or immediately before work are more directly aligned with the study’s findings.

The results also should not be confused with research on cannabis legalization more broadly. For example, a 2021 National Bureau of Economic Research working paper reported associations between recreational-marijuana legalization and lower workers’ compensation benefit receipt and non-traumatic workplace injury rates. That research examined changes following legalization at the population level, not whether individual workers used cannabis on or off the job, and it cannot determine whether cannabis itself caused the observed changes.

Overall, the Canadian study suggests that workplace safety policies should concentrate on fitness for duty and impairment rather than automatically treating off-the-clock cannabis use as an independent injury risk.