Long-term cannabis use is associated with measurably worse sleep, according to a new study led by researchers at Northwestern Medicine, even though many users do not perceive any problem. The findings challenge the widespread use of marijuana as a sleep aid, a practice that millions of Americans report.
The study followed 1,266 participants for about 35 years, beginning in young adulthood and continuing into middle age. When participants reached middle age, they wore wrist sleep monitors for one week and also completed surveys about the quality of their sleep. Because the researchers tracked people over such a long period, they were able to compare how cannabis exposure accumulated over decades with what the devices recorded years later, rather than relying on a single snapshot of use.
The results showed that lifetime cannabis exposure was linked to worse objective sleep. Heavier long-term users spent a lower share of the night asleep and experienced more sleep disruption. Participants who had used cannabis more recently showed greater sleep fragmentation and lower sleep efficiency, meaning more of their time in bed was spent awake. Recent users were also more likely to sleep for more than eight hours, a pattern that suggests longer nights do not necessarily translate into restorative rest.
One of the most striking findings concerned the gap between perception and measurement. Users did not report their sleep as worse than non-users, even though the monitors recorded more disruption. The researchers highlighted this mismatch as a central concern, since people may continue using cannabis to sleep without realizing it is affecting their rest. A subjective sense of feeling rested, in other words, did not match the physiological record captured over the week of monitoring.
The associations held after the researchers adjusted for age, race, sex, smoking, alcohol consumption and physical activity, which means these factors alone did not explain the differences observed. The study did not analyze how the drug was consumed, so it cannot say whether smoking and edibles affect sleep differently. That limitation matters for consumers, who increasingly choose products such as edibles that are often promoted as gentler or more suitable for nighttime use.
The senior author, Mercedes Carnethon of Northwestern, said the data do not support the use of cannabis as a sleep aid. Outside experts who were not involved in the research also commented on the findings. Their reactions were reported alongside the study, reinforcing the view that the results should be weighed carefully rather than treated as a final verdict on every form of use.
The sleep findings arrive alongside a separate study linking cannabis to stroke and cardiovascular risk. That research examined a heart study of about 450,000 adults and was presented at the American Heart Association's 2026 meeting. Together, the two studies add to questions about the long-term health consequences of cannabis use for people who turn to it for rest, a group that the sleep research suggests may be getting less benefit than they expect.