Study Finds No Link Between Off-Hours Pot Smoking, Workplace Accidents

Who says stoners are sloppy? 

A new study out of Canada found there was “no difference in workplace injury risk” between those who used cannabis outside the workplace and those who don’t use marijuana at all.

The longitudinal study, conducted by researchers at the University of Toronto and published in the Canadian Journal of Public Health, examined Canadian workers over a two-year period from 2018 until 2020.

“In this longitudinal study, we evaluated the relationship between past-year cannabis use and the risk of workplace injury, differentiating workers who used cannabis before and/or at work (workplace use) from those using outside of work only (non-workplace use),” the authors wrote.

Although “no statistically elevated relationship existed between non-workplace use and workplace injury,” the researchers noted that cannabis use at the workplace “was associated with an almost two-fold increase in the risk of workplace injury.”

“This pattern of findings was seen among workers in both safety-sensitive and non-safety-sensitive jobs,” they wrote.

“Study 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. 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,” the authors continued. “More specifically, only use in close temporal proximity to work appears to be a risk factor for workplace injuries, not use away from work. Our findings support Frone’s conceptual model of worker substance use and workplace productivity. Our results are also consistent with at least one previous study of employed adolescents that found workplace substance use (alcohol and cannabis combined) was associated with greater odds of workplace injury, but not general substance use. Another study found workplace cannabis use to be associated with poor work performance, while no relationship was seen for after-work use.”

Additionally, the authors said that their findings “may also explain the source of inconsistencies in prior research on cannabis use and workplace injury.” 

“Whether or not cannabis use was associated with workplace injury in past research was likely a function of the proportion of the sample engaging in workplace use,” they said. “A study including a small proportion of workers engaging in workplace use may have null findings, and a larger proportion may result in a significant positive association. Therefore, assessments of general cannabis use may not lead to appropriate conclusions.”

Whether they’re toking on the job or not, more workers are using cannabis than ever before. A study released in May found positive drug tests for cannabis in the United States had soared to an all-time high.

The Quest Diagnostics Drug Testing Index Analysis showed that a little more than 7% of drug urine samples in 2022 contained cannabis, up from 6.7% the year before.

Keith Ward, Quest Diagnostics General Manager and Vice President for Employer Solutions said, “Our 2022 Quest Diagnostics analysis shows that the overall U.S. workforce positivity rate continued to be at a historically elevated level in 2022, even as much of the nation’s workforce returned to the office post-pandemic,” said Keith Ward, general manager and vice president for employer solutions at Quest Diagnostics. “This historic rise seems to correspond with sharp increases in positivity for marijuana in both pre-employment and post-accident drug tests, suggesting that changing societal attitudes about marijuana may be impacting workplace behaviors and putting colleagues at risk. The increase in amphetamines positivity is also notable, given the addictive potential and health risks associated with this class of drugs.”