By Matthew Warren

Poor sleepers may be hoping that with the gradual liberalisation of marijuana laws around the world, a new drug to help them sleep will soon become legally available. Bad news, then, from a new diary study, published in Health Psychology, of people who take cannabis as a sleep aid. While the drug seemed to improve some aspects of sleep, it also led people to feel more tired the next day.

Most past work on the effects of marijuana on sleep has compared those who use the drug with those who abstain, which doesn’t reveal much about how an individual’s experiences change with marijuana use. So Patricia Goodhines and colleagues at Syracuse University examined how 83 university students’ sleep was affected on days when they did and didn’t take the drug over a two-week period.

Each day, the students filled in questionnaires asking how often they had used marijuana or alcohol the previous day, and their reasons for taking the drug (such as “because it makes a social gathering more fun” or “to help sleep”). Participants also rated the quality and duration of their sleep that night, and how fatigued they felt during the day.

The team found that 29 of the students used cannabis specifically as a sleep aid on at least one night of the 14-day study period (the highest frequency was 13 nights). Using the drug was related to longer duration of sleep and less time spent awake during the night, suggesting that there are some elements of sleep that cannabis may improve. But importantly, the drug didn’t help participants get to sleep any faster or improve their perceived quality of sleep – and worse, it actually increased their levels of fatigue the following day.

Alcohol use, on the other hand, had no positive or negative effects on sleep. But in this case, the study was severely underpowered: only 6 participants reported using alcohol as a sleeping aid, preventing the researchers from drawing any real conclusions.

The researchers write that their results “highlight daytime fatigue as a potential adverse short-term outcome of cannabis sleep aid use, despite its proximal sleep-related benefits”. The study period was too short to look at the longer-term consequences of cannabis use on sleep, but this is an area that is ripe for future research. It’s possible that fatigue produced by cannabis could lead participants to take more of the drug in an attempt to sleep better, for example, resulting in a vicious cycle.

Cannabis and alcohol use for sleep aid: A daily diary investigation

Matthew Warren (@MattbWarren) is Staff Writer at BPS Research Digest