An increasing number of people use cannabis right before bedtime as a sleep aid, especially since recreational use has been legalized in many states and regions in North America. Recent research, however, suggests this habit does more harm than good, leading to disrupted sleep patterns that can negatively impact mood and overall physical and mental health. New findings have linked regular cannabis use to extreme nightly sleep duration: either sleeping less than 6 hours or, on the flipside, dozing off for more than 9 hours.

Cannabis and sleep

Only two-thirds of Americans get the recommended 7-9 hours of sleep every night and more than half report daytime sleepiness virtually every day. Sleeping less than seven hours per day is associated with an increased risk of developing chronic conditions such as obesity, diabetes, high blood pressure, heart disease, stroke, and frequent mental distress.

Sleep deprivation is on the rise in the United States and other industrialized countries. The troubles and stress of modern life are also accompanied by insomnia, which has made many turn to sleep aids.

Rather than buying pills, many Americans now opt for cannabis as a form of sleep aid. Cannabis may be a better alternative, but that doesn’t mean it’s not without risks.

In a new study published in the journal Regional Anesthesia & Pain Medicine, researchers at the University of Toronto combed through a dataset of a nationally representative sample of US adults aged 20-59. Among other things, the participants reported their sleep difficulties, such as having trouble falling asleep and sleeping too much in the preceding two weeks; and whether they regularly experienced daytime sleepiness in the preceding 30 days.

The participants also reported their cannabis use. The participants were classed as recent or non-users based on whether or not they used cannabis in the past 30 days.

A grand total of 21,729 people were included in the study, representing an estimated 150 million US adults. The researchers adjusted their statistical model to account for potential influential factors such as age, weekly working hours, a history of chronic disease, weight, smoking, heavy alcohol use, and prescription medication use, as well as use of sleeping aids like barbiturates and other sedatives.

Across the entire sample, the participants slept just short of 7 hours on average. Around 12% reported less than 6 hours of sleep while only 4% reported more than 9 hours of sleep. Both extremes are suboptimal for healthy sleep.

Heavy marijuana users were 64% more likely to experience short sleep and 76% more likely to experience long sleep.

Cannabis users were 34% more likely to report short sleep and 56% more likely to report long sleep than those who hadn’t used cannabis in the preceding 30 days, the study found. Moreover, they were also 31% more likely to respond that they had difficulty falling asleep and staying asleep, as well as 29% more likely to see a doctor about sleep problems than non-users. Cannabis use didn’t seem to have any effect on daytime sleepiness.

The pattern of extreme sleep durations among cannabis users was most pronounced among heavy users — those who consumed cannabis on at least 20 out of 30 previous days. Compared to non-users, heavy users were 64% more likely to experience short sleep and 76% more likely to experience long sleep.

“Increasing prevalence of both cannabis use and sleep deprivation in the population is a potential cause for concern,” wrote the researchers led by Calvin Diep from the University of Toronto’s Department of Anesthesiology and Pain Medicine.

“Despite the current literature demonstrating mixed effects of cannabis and various cannabinoid formulations on sleep architecture and quality, these agents are being increasingly used as both prescribed and unprescribed experimental therapies for sleep disturbances.”

Since this is an observational study, the researchers had no way to establish any causal relationship that may describe a mechanism by which cannabis could cause extreme swings in sleep duration, or why some sleep too little while others sleep too much. But this isn’t the first study to report something like this. A 2016 study published in the Journal of Addictive Diseases found that daily marijuana users scored higher on the Insomnia Severity Index and sleep-disturbance measures. An earlier study from 2014  found regular marijuana users take longer to fall asleep, struggle to maintain sleep, experience  non-restorative sleep and feel daytime sleepiness. 

“Our findings highlight the need to further characterize the sleep health of regular cannabis users in the population…Sleep-wake physiology and regulation is complex and research about related endocannabinoid pathways is in its early stages,” said the researchers from the University of Toronto.