By What the Review Found
A new Cochrane review has concluded that existing evidence is too uncertain to determine whether medical cannabis improves sleep or daytime functioning in people with insomnia. The review was led by researchers from The Cochrane Associate Centre at the Universidad Hospital Italiano de Buenos Aires and the University of Manitoba.
The review included 9 studies involving 537 adults aged 18 to 76 who were treated for insomnia. Most studies focused on people with primary insomnia rather than insomnia linked to other health conditions.
In clinical settings, medical cannabis typically involves controlled, tested ratios of THC and CBD in the form of tablets, sprays or oils.
Medical cannabis showed little to no clinically meaningful improvement in sleep quality and satisfaction, total sleep time, or daytime functioning compared with placebo. Medical cannabis somewhat improved quality of life, but certainty is very low, and pooled results were compatible with anything from a slight worsening to a large improvement.
Participants taking medical cannabis were substantially more likely to experience mild adverse events, such as dry mouth and dizziness, than those on placebo, though this finding was based on a small pool of studies.
Why the Evidence Falls Short
The overall quality and certainty of the evidence were rated very low to low. The researchers cited risk of bias in the underlying studies, inconsistent results between trials, and small sample sizes as the main reasons.
Studies varied a lot in the type of cannabis product used, which limited comparability. The longest study only followed participants for 12 weeks, meaning little can be said about long-term effects.
The available data was also not very representative of broader patient groups. The data were heavily skewed towards younger people and women, who made up 72.66% of participants.
The authors therefore noted the findings may not be as applicable to men, older adults, and those with comorbidities. Insomnia itself can severely impact quality of life and make a person more vulnerable to developing anxiety or depression over time.
What the Researchers Say Comes Next
“The main message is that the research currently available is not sufficient to reliably answer whether medical cannabis helps people with insomnia,” says Dr Lucia Varela, lead author of the study from the University of Manitoba, Canada.
“This does not mean that medical cannabis is ineffective. It means that, based on the evidence we have, we cannot draw reliable conclusions about its effectiveness for insomnia in the general population,” Varela says.
“The evidence is too weak and uncertain to draw firm conclusions about the use of medical cannabis for insomnia,” says Dr Luis Garegnani, senior author from Universidad Hospital Italiano de Buenos Aires, Argentina.
“Rather than viewing the findings as either an endorsement or a rejection of medical cannabis, clinicians and patients should recognize the uncertainty and consider individual circumstances while better evidence is generated,” Garegnani says.
