Canadian workers who used cannabis at work had nearly twice the risk of workplace injury, while those who used cannabis only outside of work showed no increased injury risk.
Occupational health professionals, workplace policy makers, labor researchers
2x injury risk for workplace use; no increased risk for off-the-job use
What the researchers found
Among 2,745 Canadian workers followed from 2018-2020, workplace cannabis use (before or at work) was associated with a nearly two-fold increased risk of workplace injury (RR 1.97, 95% CI 1.32-2.93). Non-workplace cannabis use showed no significant difference in injury risk compared to non-users (RR 1.09, 95% CI 0.83-1.44). Findings were consistent for both safety-sensitive and non-safety-sensitive jobs.
Why it matters
This study provides crucial nuance to the cannabis-workplace safety debate by separating where cannabis is used. The finding that off-duty use does not increase injury risk has direct implications for workplace drug testing policies.
The numbers in context
2,745 workers; RR 1.97 (95% CI 1.32-2.93) for workplace use; RR 1.09 (95% CI 0.83-1.44) for non-workplace use; similar findings in safety-sensitive and non-safety-sensitive work
How the study worked
Longitudinal study of Canadian workers with at least two adjacent years of survey data (2018-2020, n=2,745). Exposure was classified as no use, non-workplace use, or workplace use. Workplace injury was the primary outcome, with models adjusted for personal and work variables.
What this study cannot tell us
Self-reported cannabis use and injury data. Cannot determine acute impairment at the time of injury. Relatively short follow-up period (2018-2020). Canadian workers may not represent other countries' workforces.
How to read the evidence
Longitudinal design with temporal separation of exposure and outcome, adjusted for confounders, though self-reported data limits precision.
When this study was published
Published 2023 using 2018-2020 data
The bigger picture
Workplace cannabis policies that focus on impairment during work hours rather than blanket prohibitions on any use may better target actual safety risks while respecting worker autonomy.
Questions still open
- How long before a shift does cannabis use need to stop to eliminate elevated injury risk? Would workplace impairment testing better target the actual risk than urine testing?
Common questions
Does cannabis use increase workplace injury risk?
Did the type of job matter?
Read the original research
Workplace and non-workplace cannabis use and the risk of workplace injury: Findings from a longitudinal study of Canadian workers.
Canadian journal of public health = Revue canadienne de sante publique, 114(6), 947-955
Citation
Carnide, Nancy; Landsman, Victoria; Lee, Hyunmi; Frone, Michael R; Furlan, Andrea D; Smith, Peter M. (2023). Workplace and non-workplace cannabis use and the risk of workplace injury: Findings from a longitudinal study of Canadian workers.. Canadian journal of public health = Revue canadienne de sante publique, 114(6), 947-955. https://doi.org/10.17269/s41997-023-00795-0