Medical cannabis benefits for insomnia remain uncertain, Cochrane review finds

A new Cochrane review finds that existing evidence is too uncertain to determine whether medical cannabis improves sleep or daytime functioning in people with insomnia.

Insomnia is a common sleep disorder that makes it hard to fall asleep, stay asleep, or wake up not feeling refreshed. It can have a severe impact on a person's quality of life and make a person much more vulnerable to developing anxiety or depression over time.

Existing treatment options include cognitive behavioural therapy and drugs, including antidepressants and antipsychotics, but these vary in success.

In recent years, there has been growing interest in medical cannabis as an alternative treatment for insomnia for its reported benefits in improving sleep. In clinical settings, this typically involves controlled, tested ratios of THC and CBD in the form of tablets, sprays or oils. However, the use of medical cannabis for insomnia remains contentious, and evidence is limited.

No clear evidence that medical cannabis helps

Led by researchers from The Cochrane Associate Centre at the Universidad Hospital Italiano de Buenos Aires and 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. Eight of the nine trials compared regulated medical cannabis to a placebo; one compared it to the antidepressant amitriptyline.

Medical cannabis showed little to no clinically meaningful improvement in sleep quality and satisfaction, total sleep time, or daytime functioning compared with placebo.

Participants taking medical cannabis were substantially more likely to experience mild adverse events, such as a dry mouth and dizziness, than those on placebo; but this was based on a small pool of studies.

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.

The main message is that the research currently available is not sufficient to reliably answer whether medical cannabis helps people with insomnia. 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."

Dr. Lucia Varela, lead author of the study, University of Manitoba, Canada

Poor trials downgrade the evidence

The overall quality and certainty of the evidence were rated very low to low, largely due to risk of bias in the underlying studies, inconsistent results between trials, and small sample sizes.

Studies varied a lot in the type of cannabis product used, which limited comparability, and the longest study only followed participants for 12 weeks. This means we can't say much about the 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 (72.66% of participants). Therefore, the findings may not be as applicable to men, older adults, and those with comorbidities.

The authors conclude that the evidence remains weak and uncertain, highlighting the need for higher-quality research before medical cannabis can be recommended for insomnia.

"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."