Long-Term Cannabis Use Tied to Hidden Sleep Disruption
A Northwestern Medicine study using nearly 35 years of observational data found that greater lifetime cannabis use was associated with lower sleep efficiency, more fragmented sleep, and longer time spent awake after falling asleep. Participants’ own sleep ratings did not reflect these monitor-detected disturbances, suggesting the effects may go unnoticed.
The Northwestern Medicine analysis drew on 1,266 adults in CARDIA, a U.S. community cohort launched in 1985–86 with Black and white participants. Researchers followed cannabis habits from young adulthood into middle age, then used a week of wrist-monitor data plus sleep questionnaires to compare measured rest with self-perception.
After adjustment for factors such as age, sex, race, smoking, alcohol, activity, depression, chronic illness, and other substance use, heavier lifetime cannabis use remained tied to poorer monitor-recorded sleep. The design cannot establish causation, and the study did not separate smoking from edible use.
The findings could affect adults who rely on cannabis for sleep, especially long-term users who may trust subjective restfulness. Because monitor-detected disruptions were not self-reported, some people may underestimate sleep problems and delay seeking other strategies. Clinicians and sleep educators may need to ask about cannabis use when evaluating sleep, while avoiding overstatement until causal research clarifies risks.