A new 35-year study links more cannabis use to worse measured sleep, but it is observational and cannot show cause. The CARDIA study found that more cumulative and recent cannabis use went with lower sleep percentage, more fragmented sleep and more time awake, even though cannabis use was not linked to how people rated their own sleep. Below you will find what the study measured, the side effects, the limits, and the sleep options to compare before you decide.
What did the 35-year cannabis and sleep study find?
CARDIA stands for Coronary Artery Risk Development in Young Adults. It began in 1985 and 1986 with Black and White adults in four U.S. cities, and the sleep part of the study used the year-35 exam (2020 to 2022). Of the 1,266 people analyzed, 891 wore a wrist device for seven days to measure their sleep. Funding came from the NIH’s National Heart, Lung, and Blood Institute and the Kaiser Foundation Research Institute. The Northwestern news release covers the study’s main points.
The study counted cannabis use in “cannabis-years,” where one cannabis-year is 365 days of use. “Recent use” meant use in the past 30 days. The results were adjusted for age, sex, race, cigarette smoking, alcohol, physical activity, depression, chronic conditions and other substance use.
| Sleep measure (device-recorded) | Result (odds ratio, 95% range) | What it means |
|---|---|---|
| Low sleep percentage (time asleep under 85% of time in bed), per additional cannabis-year | 1.10 (1.06 to 1.14) | Higher odds of asleep time being a smaller share of the night in bed |
| High fragmentation (top quartile), per additional cannabis-year | 1.04 (1.01 to 1.08) | Higher odds of broken-up sleep |
| Prolonged wake after sleep onset (30 minutes or more), per additional cannabis-year | 1.21 (1.10 to 1.34) | Higher odds of more time awake after falling asleep |
| Prolonged wake after sleep onset, recent users vs never or former users | 3.23 (1.44 to 7.27) | Recent users had markedly higher odds of long waking periods |
| Sleep over 8 hours vs 6 to 8 hours, recent users vs never or former users | 4.60 (1.81 to 11.70) | Recent users had higher odds of sleeping more than 8 hours |
An odds ratio above 1 means higher odds of that outcome. The range in brackets is the 95% confidence interval, which shows the plausible range for the number. Recent users also had higher odds of low sleep percentage and high fragmentation.
Why the device and the questionnaire disagree
The study used two kinds of measures. Actigraphy is a wrist-worn device that records movement through the night, so it gives an objective read on when you are asleep and when you are awake. The self-report measure was the Pittsburgh Sleep Quality Index, a questionnaire on how you think you slept, where a score above 5 counted as poor sleep.
Cannabis use was not linked to how people rated their own sleep. The gap matters because how you feel about your sleep and what the device recorded can point in different directions. The device recorded lower sleep percentage, more fragmented sleep and more time awake after falling asleep. Corresponding author Thanh-Huyen T. Vu said: “This study challenges the common belief that cannabis helps people sleep better.”
What this study cannot tell you
- It is observational. It found a link between cannabis use and worse sleep, but it cannot show that cannabis causes poor sleep.
- It did not separate smoking from edibles or other forms of cannabis.
- Patterns of use changed over the 35 years, and the device recorded only one week of sleep.
- The adjustments cover many factors, but they cannot remove every other difference between users and non-users.
Does cannabis help you fall asleep at all?
Short-term and long-term effects are different. A PMC-hosted study of adult cannabis users summarizes earlier research in which cannabis taken before sleep, often in isolated or synthetic form, was linked to shorter time to fall asleep and better sleep satisfaction. Its own survey found that current use was linked to worse subjective sleep quality, and that frequent edible use was linked to lower sleep efficiency, shorter sleep and higher PSQI scores.
The Sleep Foundation’s cannabis and sleep guide says short-term use may help you fall asleep faster, and that THC decreases the time you spend in REM sleep, the stage tied to dreaming and emotional processing. The Better Sleep Clinic points to older lab studies in which heavy users took longer to fall asleep when their brain activity was measured directly, which is a different result from how users feel.
The Better Sleep Clinic suggests that many people keep believing cannabis improves their sleep because of what they expect to happen and the drug’s relaxing feeling.
Should I smoke weed if I have insomnia?
This is a question to raise with a clinician, because the research on cannabis for long-term insomnia is limited. Recovered.org’s sleep guide says evidence for cannabis as a long-term treatment for clinical insomnia is limited and mostly anecdotal. Healthline’s cannabis sleep guide says healthcare professionals generally discourage long-term use of any sleep aid, including cannabis.
Persistent trouble sleeping can have causes a clinician can look at. Recovered.org lists pain, anxiety, hyperactivity, sleep apnea, restless legs syndrome and sleepwalking among the reasons sleep can be disrupted. For a broader look at how sleep and mood connect, read sleep hygiene and mental health and anxiety, depression and mood.
Is it okay to smoke before sleep, and how many hours before bed?
Timing changes how quickly you feel it. Healthline says smoking or vaping takes effect almost immediately, while drinks and edibles must pass through the digestive tract and may take 1 to 4 hours to begin. Healthline also says smoking and vaping are hazardous to the lungs, especially for people with asthma or other respiratory conditions.
The CARDIA results describe overall use over time, not the timing of a dose, so they cannot tell you whether a particular hour before bed is safer. If you are trying to plan around sleep, ask a clinician rather than working it out from online guides.
Is it better to sleep off a high or stay awake?
Staying awake does not make cannabis wear off faster. Kaya Life, a medical cannabis provider, says THC metabolizes at its own pace whether you are sleeping or not, and that waking up still high is a real possibility depending on how and when you use it. Its blog gives a typical window of about 3 to 4 hours for inhaled cannabis and 6 to 12 hours for edibles to fully wear off. Read the full Kaya Life blog post on sleeping high for its wording.
Is one joint a day a lot for sleep?
The studies here do not name a daily amount that is safe or harmful. They compare how often people use. The PMC-hosted paper cites a recent study in which daily cannabis users showed more insomnia symptoms and worse sleep quality than non-daily users and non-users, while non-daily users had sleep scores similar to non-users. The Sleep Foundation says the same pattern: daily users are more likely to report sleep problems than occasional users. Recovered.org adds that nightly use builds tolerance faster and can change how your body regulates sleep.
If you mean a cigarette rather than a joint, tobacco is a separate question. The CARDIA analysis adjusted for cigarette smoking, among other factors, and it was observational.
What’s worse for sleep, alcohol or weed?
Recovered.org advises against combining cannabis with alcohol or with sedatives such as benzodiazepines or opioids. The CARDIA analysis adjusted for alcohol use, among other factors, but it was observational and cannot rule out every other difference. For a ranking of which one affects your own sleep more, a clinician who knows your history is the right person to ask, and the sleep habits below help either way.
Do people who smoke weed feel happier?
General happiness is not what these studies measured. The 2026 Neuropsychopharmacology trial was a randomized, double-blind, placebo-controlled study of 44 healthy adults aged 21 to 55, using smoked cannabis at 0%, 4% and 10% THC. It rated how people felt right after smoking. Frequent users rated the “Like” and “Take again” items higher and used more cannabis than occasional users. Occasional-use males rated “High,” sedation, dysphoric arousal and “Bad effect” higher at the active strengths. The authors note the study was small and several findings were exploratory. If your question is about mood in general, the anxiety, depression and mood section of this site is the better place to start.
What are the side effects, and who should be most careful?
For how the FDA regulates cannabis and CBD products, see FDA regulation of cannabis and cannabis-derived products. The table below lists the risks described in the guides above.
| Risk | What the sources say | Source |
|---|---|---|
| Lung irritation | Smoking and vaping are hazardous to the lungs, especially with asthma or other respiratory conditions | Healthline |
| Too much at once | Fear, panic, nausea, depression, or a faster heart rate can follow intoxication | Sleep Foundation |
| Less REM sleep | THC decreases time in REM sleep, which recovered.org describes as essential for memory consolidation and mood regulation; see sleep and memory | Sleep Foundation; recovered.org |
| Tolerance | The same dose becomes less effective over time, so people may need more | recovered.org |
| Withdrawal when stopping | Stopping suddenly may bring rebound insomnia, vivid dreams and restlessness; recovered.org advises tapering rather than quitting abruptly | recovered.org |
| Long-term brain effects | Possible effects on learning, memory and focus; experts agree people under 25 face greater risk of long-term consequences | Healthline |
| Mixing substances | Avoid combining cannabis with alcohol or sedatives such as benzodiazepines or opioids | recovered.org |
| Children and pets | Cannabis can be harmful to children and pets; keep it in a secure spot | Sleep Foundation |
What are your options for better sleep?
The options below sit side by side. Each one suits a different question, and you can use more than one.
| Option | What the sources say | Next step |
|---|---|---|
| CBT-I (cognitive behavioral therapy for insomnia) | Recovered.org calls CBT-I the gold standard for chronic insomnia. The Better Sleep Clinic says speaking with a doctor or sleep specialist about CBT-I is a safer and more effective approach than relying on cannabis. | Ask a clinician whether CBT-I is right for your situation |
| Sleep habits | CARDIA co-author Kristen Knutson’s advice is a regular bedtime and a cool, dark, quiet bedroom. Recovered.org adds limiting screens and keeping a calm sleep environment. See sleep hygiene and mental health for the research. | Start with a regular bedtime tonight |
| Talking with a clinician | Persistent insomnia can have causes like pain, anxiety, sleep apnea, restless legs or parasomnias, which a clinician can assess | Book a visit and bring a week of sleep notes |
| If you use cannabis now | Recovered.org suggests tracking how your sleep changes, pausing use regularly, avoiding alcohol and sedatives, and tapering rather than stopping abruptly | Talk with a clinician before changing how you use it |
If you want to know more about the ingredients that come up in CBD-based sleep discussions, see CBD benefits evidence (our research library).
What to bring to a clinician
- A week of sleep notes: bedtime, wake time, how often you woke up, and how rested you felt.
- How often you use cannabis, in what form, and whether you use alcohol or other sleep aids too.
- Whether you have pain, anxiety, breathing problems at night, or restless legs.
- Whether CBT-I is an option where you live.
By the Global MH Summit Research Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.