Cannabis use at work nearly doubled injury risk, but off-the-job use did not
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.
Quick Facts
What This Study 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.
Key Numbers
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 They Did This
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.
Why This Research 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 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.
What This Study Doesn't 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.
Questions This Raises
- ?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?
Trust & Context
- Key Stat:
- 2x injury risk for workplace use; no increased risk for off-the-job use
- Evidence Grade:
- Longitudinal design with temporal separation of exposure and outcome, adjusted for confounders, though self-reported data limits precision.
- Study Age:
- Published 2023 using 2018-2020 data
- Original Title:
- Workplace and non-workplace cannabis use and the risk of workplace injury: Findings from a longitudinal study of Canadian workers.
- Published In:
- Canadian journal of public health = Revue canadienne de sante publique, 114(6), 947-955 (2023)
- Authors:
- Carnide, Nancy(2), Landsman, Victoria, Lee, Hyunmi(2), Frone, Michael R, Furlan, Andrea D, Smith, Peter M
- Database ID:
- RTHC-04450
Evidence Hierarchy
Follows a group of people over time to track how outcomes develop.
What do these levels mean? →Frequently Asked Questions
Does cannabis use increase workplace injury risk?
It depends on when it is used. Using cannabis before or during work nearly doubled injury risk (RR 1.97), but using cannabis only outside of work showed no increased risk (RR 1.09) compared to non-users.
Did the type of job matter?
No. The pattern was similar for workers in safety-sensitive and non-safety-sensitive jobs, with workplace use increasing risk and off-duty use showing no increased risk in both groups.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-04450APA
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
MLA
Carnide, Nancy, et al. "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, 2023. https://doi.org/10.17269/s41997-023-00795-0
RethinkTHC
RethinkTHC Research Database. "Workplace and non-workplace cannabis use and the risk of wor..." RTHC-04450. Retrieved from https://rethinkthc.com/research/carnide-2023-workplace-and-nonworkplace-cannabis
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.