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Scientists have found that sleep became very disrupted when regular cannabis users withdrew from the drug.Chris Young/The Globe and Mail

At least once a week, I hear from patients that smoking marijuana helps them to relax and to sleep. I know that other clinicians hear the same thing because they ask me about it at insomnia workshops. Does cannabis really improve sleep?

Several studies done in the 1970s examined the effects of smoked marijuana on objective sleep patterns, measured using polysomnography. This method of overnight recording involves the tracking of brain waves, eye movements and muscle tone in order to distinguish the sleep stages and their pattern of occurrence throughout the night.

Contrary to popular belief, smoking marijuana did not necessarily make it easier to get to sleep. Participants in some studies fell asleep faster while those in other studies took somewhat longer to fall asleep. There were also inconsistent effects on the amount of slow wave sleep, or deep sleep. The most consistent finding across these studies was that marijuana was associated with a reduction in rapid eye movement (REM) sleep, the stage in which most of our dreaming occurs.

The main active constituent of marijuana was isolated in 1964 as tetrahydrocannabinol (THC). Since then, dozens of other constituents have been characterized, including cannabidiol (CBD), an important component thought to have muscle relaxant, anti-inflammatory and analgesic effects.

Fast-forward to the 21st century: It is now possible to create cannabis-based medicines with certain doses and combinations of THC and CBD. By having control over the specific drug composition, better studies on the effects of cannabis on sleep are possible.

However, few researchers have explored this. Rather, the studies today are mainly looking for effects on symptoms such as pain, muscle spasms and appetite; sleep is sometimes asked about, but rarely measured with polysomnography.

What we take away from these newer studies is that participants report a positive effect on their sleep with these compounds and that the THC component of cannabis may be more responsible for this than the CBD. There are insufficient data to say anything about the effect on sleep stages.

What we do know is that sleep becomes very disrupted when people who are using cannabis on a regular basis start withdrawing from it. Sleep difficulty and strange dreams are prominent withdrawal effects. Polysomnographic data show that it takes longer for people to fall asleep, their sleep is disrupted, deep sleep is reduced and REM sleep is increased.

What seems like a simple question – "Does cannabis really improve sleep?" – does not have a simple answer. Well-designed studies with good measurement of sleep are lacking. What research has been done is complicated by variations in the dose and chemical composition of cannabis, method of use (smoked, oral spray, capsule), time of use in relation to bedtime, the participants' pattern of prior exposure to cannabis, and their medical and sleep histories.

Although the general feeling among users is that cannabis helps their sleep, there is as yet no clear evidence of this from research. This does not mean that the effects are absent. The experience of sleep is a subjective and personal thing, and all the reports of people's improved sleep with cannabis cannot be discounted. It is likely that some positive effects are present but clouded by problems in research design and measurement.

What's clear is that when cannabis is stopped after regular use, poor sleep is likely to occur, including more stage REM accompanied by weird dreams. This we can all agree on and, in a backward sort of way, it speaks to the substantial effects of cannabis on sleep.

Dr. Judith Davidson is a clinical psychologist and sleep researcher. She works with the Kingston Family Health Team and Queen's University at Kingston. She is the author of Sink into Sleep: A Step-by-Step Workbook for Reversing Insomnia. You can follow her on Facebook and on Twitter at @JudithRDavidson

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