Weed’s growing acceptability, albeit still federally illegal in the U.S., may be causing U.S. employers concerned about effects on job performance to spend billions of dollars to pin down potential impacts. But should they consider a different tack before spending so much money?

A recent study out of the U.S. suggests that not all cannabis consumption should be viewed in the same way, at least when it comes to when people use and how that may influence job performance. “Given the popularity of cannabis on a national level, it should be of little surprise that organizations spend billions of dollars each year addressing what many believe is a problem,” Jeremy Bernerth, a management professor at San Diego State University, says in a university post.

Recently published in Group & Organization Management, the study found a negative correlation — meaning a decline in performance — between workers who used cannabis before (within two hours of their shift) and during work with task performance. However, there was no relationship between using cannabis after work and performance on the job.

“Our research suggests there is no evidence that after-work usage compromises work performance as assessed by one’s direct supervisor,” notes Bernerth, who, along with H. Jack Walker, a management professor at Auburn University, conducted the study.

Bernerth and Walker sought to determine if the common assumption that consuming weed at and during work causes substandard work performance was, in fact, true.

Supervisors were more likely to report reduced helpfulness toward the organization and increased counterproductive work behaviours among employees who reported using cannabis before and during work hours. / Photo: Getty Images Getty Images

Surveying 281 employees and their direct supervisors, the researchers considered marijuana’s influence on performance, especially as it related to core job requirements, helping colleagues or their organizations, and counterproductive behaviour on the job. Each employee was asked about cannabis use frequency and timing related to their work shifts.

Supervisors were more likely to report reduced helpfulness toward the organization and increased counterproductive work behaviours among employees who reported using cannabis before and during work hours, the researchers note. With use after work, again, “the results showed no discernable effects.”

Employers have substance policies and may use testing to determine the presence of matabolites, which some may equate to impairment. / Photo: UrosPoteko / iStock / Getty Images Plus / Photo: UrosPoteko / iStock / Getty Images Plus

Employers have substance policies and may use testing to determine the presence of matabolites, which some may equate to impairment.

“Since our study shows that off-the-job cannabis use has little to no impact on workplace performance, organizations will be hard-pressed to provide legally defensible justifications for the continuation of policies prohibiting all forms of cannabis use,” Bernerth notes.

“We hope this research can provide organizations with the necessary information to structure their substance policies,” he adds.