Getting roughly eight hours of sleep is crucial for most of us to avoid feeling like a zombie at work the next day. While some people use caffeine to keep alert during the day, others have turned to cannabis as a sleep aid.

Now, a large-scale study on the effects of cannabis on sleep duration and quality has called into question the drug's reputation as a beneficial pre-slumber choice.

Data on cannabis use and sleep duration for 21,729 adults were obtained from the US National Health and Nutrition Examination Survey (NHANES), a cross-sectional survey designed by the National Center for Health Statistics (NCHS) and the Centers for Disease Control and Prevention (CDC).

The authors of the new study, led by researchers at the University of Toronto in Canada, wanted to determine the relationship between recent cannabis use and sleep duration in a nationally representative sample from the US. Participants were required to report their age range, race, sex, education post high school, average hours worked per week, and other health-related variables.

Sleep duration was categorized as short, optimal, or long, with short sleep defined as less than 6 hours, and long sleep defined as more than 9 hours on average weeknights or worknights.

Sleep quality measures were also part of the survey, with questions relating to difficulty falling asleep, ability to stay asleep, sleeping too much in the past two weeks, and whether participants had consulted a physician about sleeping issues.

For cannabis use, participants were defined as 'users' if they had used cannabis in the past 30 days, which ended up being a total of 3,132 individuals or 14.5 percent of people surveyed. These users were then further categorized into how much they'd smoked in the last 30 days – 'moderate use' was less than 20 times, and 'heavy use' was more than 20 times.

The cannabis users surveyed were 34 percent more likely to report sleeping fewer than 6 hours per night when compared to non-users, as well as being 56 percent more likely to report sleeping more than 9 hours when compared to non-users, after accounting for potential confounding factors.

Recent cannabis users were also more likely to report having difficulty falling asleep, staying asleep, sleeping too much in the past two weeks, and having ever told a physician about sleeping problems. However, cannabis exposure was not associated with frequent daytime sleepiness.

"We determined there to be a possible exposure-response relationship between frequency of use and sleep duration; heavy users were at the greatest risk of both extremes of nightly sleep duration compared with non-users," the team writes.

"With our cross-sectional analyses, we can only speculate that these findings may be related to an unknown consequence of repeated cannabis exposure alone or may be a reflection of other underlying sociodemographic or health factors."

Previous findings have shown mixed results pertaining to the effectiveness of cannabis as a sleeping aid, with some studies showing that even a single cannabis exposure can reduce sleep-onset latency, increase total sleep time, and report less disruption once asleep.

"Despite insomnia being one of the most cited reasons for self-medication with cannabis or cannabinoids, the evidence base is overall inconsistent and of poor quality, as described in a recent systematic review," the authors write.

Overall, the researchers wanted to get a glimpse into an association between sleep disturbances and recent cannabis use, especially now that it's becoming more widely available. They speculate that with repeated use, the body can become more used to the drug, and actually increase sleep disruption.

There's still much we don't know about how cannabis and its various compounds affect our sleep, the researchers warn.

"A better understanding of the endocannabinoid-mediated effects on sleep can inform development of clinical guidelines to target improved long term health outcomes at the patient and population levels," they write.

In the US, sleep deprivation has become a major public health concern, with only two-thirds of the population meeting the 7-9 hours of sleep per night recommendation, and almost half of American adults reporting daytime sleepiness every day.

In addition to this, more widespread legalization and decriminalization of cannabis in the US and Canada has led to a large uptake since the early 2000s, with 45 million reported users in 2019.

"Insufficient sleep in the modern world is a growing public health issue and sleep disturbances can be a major risk factor for initiating cannabis use," the authors caution.

"This can perpetuate cycles of increased cannabis use, progressive sleep disturbances, and acute cessation leading to withdrawal which may add further negative effects to sleep architecture and quality."

The study was published in the journal Regional Anesthesia & Pain Medicine.