A good night’s sleep is something millions of people struggle to achieve, and cannabis has become an increasingly popular remedy. But what if it is doing more harm than good? A new study from Northwestern Medicine suggests that cannabis users may experience poorer sleep quality without even realising it, raising questions about whether marijuana is truly an effective sleep aid.

Published on 9 October in JAMA Network Open, the study found that both long-term and recent cannabis use were associated with disrupted sleep. Surprisingly, participants who used cannabis generally believed they slept just as well as non-users, despite objective measurements suggesting otherwise.

Researchers analysed data from 1,266 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, which has followed American adults for nearly 35 years. Participants’ cannabis use was tracked from young adulthood into middle age. Researchers then used wrist-worn sleep monitors for seven nights, alongside questionnaires, to compare actual sleep patterns with participants’ perceptions.

The results revealed a striking disconnect. People with greater lifetime cannabis exposure spent a smaller proportion of the night asleep, experienced more frequent sleep interruptions and remained awake longer after initially falling asleep. Recent cannabis users showed similar difficulties and were also more likely to sleep longer than eight hours per night.

“This study challenges the common belief that cannabis helps people sleep better,” said Dr. Thanh-Huyen T. Vu, the study’s corresponding author and a research associate professor of preventive medicine at Northwestern University. “Our findings suggest cannabis may actually be associated with poorer sleep quality, even if people don’t perceive those changes.”

The association remained even after researchers accounted for factors such as age, smoking, alcohol consumption, physical activity, depression and chronic health conditions. However, the study could not establish whether cannabis directly causes sleep disturbances. It also did not distinguish between smoking cannabis and consuming edibles, leaving questions about whether different methods of consumption affect sleep differently.

“Our data do not support the belief that cannabis is helpful as a sleep aid,” said senior author Mercedes R. Carnethon, chair of preventive medicine at Northwestern. With cannabis becoming more widely available and socially accepted, the researchers emphasised the importance of understanding its potential long-term health effects, particularly when users may be unaware of changes in their sleep.

For those seeking better rest, sleep specialist Kristen L. Knutson recommends sticking to proven habits rather than relying on cannabis. Maintaining a consistent bedtime, keeping bedrooms cool, dark and quiet, and avoiding screens before bed can all help. Relaxing activities such as reading, meditation or a warm shower may also encourage restful sleep. Anyone experiencing persistent sleep difficulties or loud snoring should consult a healthcare professional to investigate possible underlying sleep disorders.

More information: Thanh-Huyen T. Vu et al, Recent and Cumulative Cannabis Use and Sleep in Middle-Aged Adults, JAMA Network Open. DOI: 10.1001/jamanetworkopen.2026.38303

Journal information: JAMA Network Open Provided by Northwestern University