One in five jobs in the developed world requires night shifts or frequent day-night rotations. By asking workers to be active and alert when their natural cycles demand the opposite, these jobs can end up exerting a great toll on workers’ physical and mental health. Unsurprisingly, shift-workers perform worse and hold higher rates of work-related injuries compared to those working in standard schedules.
These problems could be aggravated by the use of drugs that disrupt aspects of memory, attention and motor coordination. This is specially relevant in the case of cannabis, which not only holds many of these effects, but is also one of the most commonly used drugs today. Up to 2 million Americans, or 1.6% of the workforce, report having been under the influence of cannabis at work, and the drug accounts for nearly 50% of all positive work-related urine screens.
In light of this, many have expressed concerns about the extent of cannabis intoxication at work. But what if cannabis could actually help those working nonstandard schedules?
This is the provocative hypothesis that is raised in a recent study conducted by researchers from Columbia University.
Dr. Carl Hart and colleagues invited ten experienced cannabis smokers to a 23 day long residential study. The participants followed a strict schedule, in which they were asked to smoke a single cannabis cigarette with varying THC concentrations or a placebo cigarette one hour after waking up. They then went through a simulated desk office job in either a day or night schedule. Every three days they rotated the cannabis treatment and work shift, and throughout the experience, the researchers collected measures of sleep quality, subjective well-being and cognitive performance (which were the actual 'work tasks'). The researchers were interested in measuring the impact of cannabis on these transitions.
Results showed that participants undergoing night shift on placebo had worse performance on short-and long-term memory tasks, as well as those measuring concentration and impulse inhibition, compared to placebo day shifts. The workers reported feeling less confident in themselves and more tired and miserable. They were also less satisfied with their sleep, with objective measures of sleep confirming that participants were indeed sleeping less.
Contrary to the researchers’ expectations, cannabis actually improved the performance on night shifts. The cognitive tests revealed similar performances to those of day shifts, with participants feeling higher self-confidence and more stimulated (also less tired and miserable). In addition, total sleep time and subjective sleep quality improved on the first night of the 3 night shift when participants were given the more potent cannabis dose (3.56% THC).
Interestingly enough, the positive effects of cannabis were confined to the night shifts. If anything, there was a slight reduction in performance during the day shifts where participants were given cannabis. The drug did not affect sleep during these periods either.
This led the authors to hypothesize that the effects of cannabis on night shift performance might be indirectly caused by the improvement in sleep, and not directly due to its acute effects. This is an interesting idea, which is in line with a growing, still disjointed, body of evidence showing that cannabis can have diverse effects on sleep (a good review on the topic can be found here).
Two caveats to this study should be noted. First, the placebo effect was far from perfect, as patients were quite able to distinguish between cannabis and placebo. This could be more problematic given that participants were aware of the study goals. Secondly, because we are talking of regular users, it is quite plausible that the negative effects reported on placebo nights reflected withdrawal effects, meaning that all cannabis did was counteract them. As the authors write, more research is needed before broader conclusions can be taken.
The work described in this article was funded by the U.S. National Institute on Drug Abuse, and can be retrieved from the academic journal Drug and Alcohol Dependence.
Featured image by Leonardo Angelini.