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Marijuana may be making sleep quality worse, despite its widespread use as a sleep aid, a recent Northwestern Medicine study found.
The findings of the study, which included 1,266 participants, showed that both lifetime and recent cannabis users objectively had worse sleep quality, although they did not report their sleep to be worse.
Participants were monitored for almost 35 years, from young adulthood into middle age, with scientists tracking their use of cannabis over time.
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In middle age, participants wore a sleep monitor on their wrist for a week and filled out surveys about their sleep quality.
This allowed researchers to compare objective and subjective reports of participants’ sleep.
A recent Northwestern Medicine study found that cannabis use does not improve sleep. Instead, it actually worsens people’s quality of sleep. (iStock)
“Our data do not support the belief that cannabis is helpful as a sleep aid,” said senior study author Mercedes R. Carnethon, Ph.D., as Northwestern Now reported.
“As cannabis becomes increasingly available and accepted, it’s important to better understand its long-term associations with health behaviors such as sleep,” Carnethon added.
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Among all participants, a greater lifetime exposure to marijuana was linked to worse objective sleep quality.
Those who had a higher cannabis usage over time were generally asleep for a lower percentage of the night and experienced more sleep disruption.
The study found that recent cannabis users had more sleep disruption. (iStock)
Similarly, recent cannabis users were more likely to have more sleep fragmentation and lower sleep efficiency, compared to people who never used the substance.
The study also found there was a much higher chance that recent cannabis users would sleep longer than eight hours per night.
The study discusses the differences between objective and subjective reports of sleep quality.
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“What makes this study particularly interesting is that participants who used cannabis demonstrated objectively poorer sleep, yet their own assessments of sleep quality did not reflect those differences,” Alfred Joshua, M.D., a board-certified emergency medicine physician based in California, told Fox News Digital. (He was not involved with the new study.)
“In other words, someone may believe marijuana is helping them sleep, while objective measurements suggest otherwise.”
Scientists say more research needs to be done to determine the long-term effects of cannabis use on sleep. (iStock)
Researchers considered multiple outside factors including age, race, sex, smoking frequency, alcohol consumption, physical activity and more.
Even with these factors taken into account, the study found a consistent correlation between cannabis use and poorer objectively measured sleep.
The mode of cannabis consumption, such as smoking versus taking edibles, was not considered.
“These findings raise important questions.”
“It is not surprising that the actual quality of sleep of these subjects, after chronic marijuana use, is poor compared to those who do not smoke marijuana because people who claim that they need to smoke marijuana before they go to sleep, in order to relax, are only kidding themselves,” board-certified psychiatrist Carole Lieberman, M.D., of California told Fox News Digital. (She, too, was not affiliated with the new study.)
Participants in a new study often did not report having poorer sleep quality even though data from their wrist monitors showed they had objectively worse sleep quality. (iStock)
“It is more a psychological addiction than a physical one,” she added. “They enjoy the high that they get right away, but the marijuana doesn’t help them to sleep better.”
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“The researchers found that greater cumulative cannabis exposure was associated with reduced sleep efficiency, increased sleep fragmentation and more time spent awake after initially falling asleep,” said Joshua, the board-certified emergency medicine physician.
“These findings raise important questions about whether habitual marijuana use is a sustainable strategy for managing sleep problems,” he added.
Fox News Digital recently reported on other cannabis findings.
A study of nearly 450,000 American adults, for instance, linked cannabis use to an increased risk of stroke and cardiovascular disease.
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The findings were scheduled for presentation at the American Heart Association’s Scientific Sessions 2026 in Chicago Nov. 6–9. They showed that both casual and heavy marijuana users have higher odds of heart conditions compared to non-users.
Khloe Quill of Fox News Digital contributed reporting.