Study links cannabis use to poorer sleep quality

Although many people use marijuana to help them sleep, a Northwestern Medicine study suggests frequent or long-term use may be associated with worse sleep quality.

The study followed 1,266 people for nearly 35 years, tracking cannabis use from young adulthood into middle age. At the end of the study period, participants wore wrist monitors for a week and answered questions about their sleep. The researchers found that cannabis users had poorer sleep according to the monitor readings, even though they did not rate their sleep as worse.

Greater lifetime cannabis exposure was associated with spending a smaller share of the night asleep and experiencing more interruptions. Recent users also tended to have more fragmented sleep and lower sleep efficiency than people who had never used cannabis. They were also more likely to sleep for more than eight hours a night.

“Our data do not support the belief that cannabis is helpful as a sleep aid,” said senior study author Mercedes R. Carnethon. She said that as cannabis becomes more accessible and accepted, its long-term relationship with health habits such as sleep deserves closer study.

Alfred Joshua, an emergency medicine physician who was not involved in the research, said the gap between monitor readings and participants’ own assessments stood out. People may feel that marijuana helps them sleep, he said, while objective measurements indicate poorer sleep.

The researchers accounted for factors including age, race, sex, smoking, alcohol use and physical activity. The association between cannabis use and poorer measured sleep remained. They did not examine whether the findings differed based on how cannabis was consumed, such as by smoking or eating it.

Psychiatrist Carole Lieberman, who was also not involved in the study, said people may mistake the relaxing or euphoric effects of marijuana for improved sleep. Joshua noted that greater cumulative use was linked with more time awake after initially falling asleep, as well as lower sleep efficiency and more sleep interruptions. He said the findings raise questions about relying on regular cannabis use to manage sleep problems.

Other recent research has linked cannabis use with increased odds of stroke and cardiovascular disease. Those findings, involving nearly 450,000 U.S. adults, were due to be presented at the American Heart Association’s Scientific Sessions in Chicago in November 2026.