THC before bedtime might not be the sleep fix you think it is

Cannabis is among the most commonly self-reported sleep aids in the U.S., yet the science behind how its primary psychoactive compound affects the sleeping brain is murky. 

A new pilot study from a research team lead by Oregon Institute of Occupational Health Sciences (OccHealthSci) Assistant Professor Nicole Bowles takes a careful, controlled look at what happens physiologically when people use THC before bed—and the findings complicate the popular narrative.

The study, “Delta-9-tetrahydrocannabinol (THC) before bedtime: Feasibility and mechanistic pilot study on sleep and cardiac autonomic activity,” published in the Journal of Sleep Research, is a feasibility and mechanistic pilot study—a small, tightly controlled investigation designed to test methods and generate hypotheses, not to draw conclusions. With just 18 participants divided into individuals that use cannabis regularly and those that rarely, if ever, use cannabis, the research is in too perlimiary to make definitive claims. What Dr. Bowles and team do offer are the methodological foundations and some intriguing initial results worth pursuing in larger, follow-up studies.

Participants underwent two weeks of sleep stabilization before spending three nights in a clinical laboratory at Oregon Health and Sciences University, where the research team monitored their brain activity and heart function. On one night they received a placebo; on another, a 10-milligram oral dose of dronabinol, a synthetic form of THC, taken an hour before bed.

The results contradict the popular claim that THC is good for sleep. Under controlled conditions, THC actually increased the time it took participants to fall asleep and delayed the onset of REM sleep, the stage most associated with dreaming and emotional memory consolidation.

Perhaps the most striking preliminary finding involved the heart. THC produced large, statistically relevant reductions in heart rate variability across all sleep stages in both groups. Lower nocturnal heart rate variability has been associated with elevated cardiovascular risk, and the effect sizes here were clinically meaningful even from a single dose. Dr. Bowles notes that causality cannot be inferred from this pilot study, but the results warrant follow-up.

At home, individuals that regularly use cannabis also showed shorter total sleep time and more fragmented sleep than those with no history of cannabis use, even when both groups were held to an eight-hour window in bed.

According to Dr. Bowles, what this study offers is not a verdict on cannabis and sleep but a well-marked path towards reaching one. It is a starting point — evidence that controlled research in this area is feasible, that the physiological effects of THC during sleep are measurable and meaningful, and that the assumption that cannabis makes for better sleep deserves far more scientific scrutiny than it has received.

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This work was supported by the American Academy of Sleep Medicine, the National Institutes of Health (K01 HL151745, R35 HL 155681, T32HL 083808) and the Division of Consumer and Business Services of the State of Oregon (ORS 656.630). 

Gonzalez, Joshua E., et al. "Delta‐9‐Tetrahydrocannabinol (THC) Before Bedtime: Feasibility and Mechanistic Pilot Study on Sleep and Cardiac Autonomic Activity." Journal of Sleep Research (2026): e70298.