A new long-term study from Northwestern Medicine has revealed that both lifetime and recent cannabis use are associated with worse sleep quality among users, contradicting the common belief that cannabis aids in sleep. Published on October 9, 2026, in JAMA Network Open, the research found that individuals using cannabis did not perceive their sleep to be of poorer quality compared to non-users, despite objective measurements indicating otherwise.
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This study follows participants over nearly 35 years, from young adulthood into middle age, marking it as one of the most extensive investigations of its kind. The participants wore wrist-based sleep monitors for a full week and completed sleep surveys, enabling a comparison of subjective sleep perceptions with objective data. The monitored data showed that higher lifetime cannabis exposure correlated with less efficient sleep, more sleep fragmentation, and longer periods of wakefulness after initially falling asleep.
The research utilized data from the Coronary Artery Risk Development in Young Adults (CARDIA) Study, initiated in 1985 and 1986, which tracks Black and white adults across the United States. Among the 1,266 participants analyzed, those with a greater history of cannabis use reported similar subjective sleep quality as non-users, despite significant discrepancies in measured sleep quality.
Dr. Thanh-Huyen T. Vu, a research associate professor at Northwestern University Feinberg School of Medicine, noted that the significant finding was the mismatch between the participants' self-reported sleep quality and the data collected by the wearable devices.
The study emphasizes that in the absence of conscious recognition of sleep disruptions caused by cannabis, users may continue to rely on it as a sleep aid, unaware of its potential negative impact on their sleep architecture. Dr. Vu stated, "This study challenges the common belief that cannabis helps people sleep better."
While the research indicates an association between cannabis use and poorer sleep quality, it does not establish a definitive causal relationship. The authors acknowledged that many factors could influence sleep, and adjustments were made for variables known to impact sleep such as age, sex, race, and substance use.
Mercedes R. Carnethon, chair of the department of preventive medicine at Feinberg, emphasized the importance of understanding cannabis's long-term effects as its use becomes more widespread. Despite the findings, the study has some limitations, including not distinguishing between different methods of cannabis consumption, which could affect outcomes.
For individuals seeking better sleep without using cannabis, the authors recommend established practices, such as maintaining a regular bedtime, creating a cool and dark sleeping environment, and avoiding screens before bed. These strategies are supported by decades of sleep research and do not carry the risk of disrupting rest, unlike cannabis use.