Cannabinoids change sleep as well as sleepiness
In a small insomnia trial, a THC–CBD preparation reduced total and REM sleep without improving reported sleep quality. A separate CBD trial found improved well-being but little change in most sleep outcomes. Meanwhile, Spanish siesta research associates different nap lengths with different metabolic patterns. These studies concern distinct forms of rest and do not establish a cannabis-based siesta tradition.
Spanish nap research distinguishes duration and lifestyle
The 2023 ONTIME study examined 3,275 adults from a Mediterranean population. Thirty-five percent usually took siestas. Longer naps, defined in the study as more than thirty minutes, were associated with higher body-mass index, waist circumference, glucose and blood-pressure measures, alongside a higher prevalence of metabolic syndrome. Shorter naps showed a different pattern, including a lower probability of elevated systolic blood pressure than no naps.
This was a cross-sectional study, so it cannot prove that a long nap caused those outcomes. Smoking, meal size and the timing of sleep and eating helped explain the associations. Its contribution is to show that a siesta is not one uniform behaviour. It did not test cannabis.
A THC–CBD sleep trial found less total and REM sleep
In a pilot crossover trial of twenty people with diagnosed insomnia, researchers compared a single oral THC–CBD preparation with placebo using detailed sleep recordings. Total sleep time was about twenty-five minutes shorter with the cannabinoid preparation, and REM sleep was about thirty-four minutes shorter. Subjective sleep quality did not improve.
Objective next-day alertness and the tested cognitive outcomes did not differ, while self-reported sleepiness increased slightly. The study concerns one preparation and one exposure in a small group. Its value is the direct demonstration that a cannabinoid-related change in how someone feels need not mean longer or better-rated sleep.
CBD alone also needs its own evidence
A 2024 randomised pilot trial analysed thirty people with moderate-to-severe insomnia over two weeks. CBD did not outperform placebo on insomnia severity or most sleep outcomes, although well-being and some secondary measures showed benefits.
The distinction matters: an improvement in well-being is not an invented result, but neither is it the same as resolving insomnia. A study can produce a mixed pattern that is more informative than a simple sleep-aid label.
Sleep and metabolic findings
In the small THC–CBD insomnia trial, total sleep fell by about 24.5 minutes and REM sleep by 33.9 minutes compared with placebo. Participants did not report better sleep quality. The separate two-week CBD trial found no improvement in insomnia severity or most sleep measures, despite improved wellbeing.
The Spanish siesta study associated naps longer than 30 minutes with less favourable metabolic measures; its observational design cannot establish that naps caused those differences.
Sources & further reading
General information, not individual legal or medical advice.