Many people reach for cannabis the way their parents reached for a nightcap. A gummy, a vape, a puff before bed, and the day feels like it finally lets go.
Some say it is the only thing that gets them to sleep at all. But a new 35-year study of more than 1,200 adults suggests cannabis may quietly disrupt the sleep it is meant to deliver, even when users feel fine the next morning.
The findings were published October 9, 2026 in JAMA Network Open. Researchers at Northwestern University's Feinberg School of Medicine tracked participants from the CARDIA heart-health study from young adulthood into their late fifties and early sixties.
In middle age, each person wore a wrist device for a week to measure sleep objectively. They also filled out standard sleep questionnaires.
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Objective sleep got worse the more people had used cannabis
The pattern was consistent. People with more years of cannabis use spent a smaller share of the night actually asleep, had more fragmented sleep, and lay awake longer when they woke in the middle of the night.
Recent users, meaning those who had used in the past 30 days, had the clearest disruption. For every extra year of lifetime cannabis exposure, the odds of lying awake for 30 minutes or more during the night rose by about 21 percent.
Recent users were more than three times as likely as never-users to have those long middle-of-the-night awakenings. They were also more likely to sleep over eight hours, which in middle age is often a sign of poor-quality sleep rather than extra rest.
Users felt their sleep was fine
Here is where the study turns most of all. On the Pittsburgh Sleep Quality Index, a standard questionnaire, cannabis users did not rate their sleep as worse than non-users.
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The wrist monitor said otherwise. According to Northwestern University, the wearable device detected more nighttime disruption among participants with long-term cannabis exposure. Yet those participants generally did not report worse sleep themselves.
That gap matters because many people choose cannabis specifically for sleep. CDC data released in April 2026 found that about 4 percent of US adults use cannabis most days or every day to help them sleep.
What the study can and cannot show
This is an observational study, so it points to a strong link, not proof that cannabis caused the disrupted sleep. The researchers adjusted for age, sex, race, alcohol, nicotine, physical activity, depression and medications.
Other lifestyle factors could still play a role. The strength of the finding is the length of the follow-up and the use of a wearable rather than self-reports alone.
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The authors conclude that both long-term and recent cannabis use were tied to poorer objective sleep quality, even when users said they slept just fine. If you use cannabis to fall asleep and feel it works, your subjective experience may be missing what is happening overnight.
Talking to your doctor about safer, evidence-backed options for insomnia is a reasonable next step.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.