A recent Cochrane review has concluded the evidence behind medical cannabis for insomnia is ‘too weak and uncertain’ to draw reliable conclusions about its effectiveness.
An international team of researchers has found there is insufficient evidence to determine whether medical cannabis can improve sleep or daytime functioning in people with insomnia.
The researchers said they had little confidence in the evidence exploring the use of cannabis for insomnia after amalgamating the results of nine studies involving more than 500 participants. Their findings were published in the Cochrane Database of Systematic Reviews.
“The main message is that the research currently available is not sufficient to reliably answer whether medical cannabis helps people with insomnia,” said Dr Lucia Varela, a neurologist and researcher from the University of Manitoba, Canada, who was the lead author on the new research. “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.”
An extensive database search resulted in nine studies published between 2010 and 2025 that were included in the current synthesis. These studies involved 537 adults (mean age 44.78 years, 72.66% women) with a diagnosis of insomnia. Most studies were small and enrolled fewer than 50 participants; only two trials had more than 100 participants.
Eight studies compared medical cannabis – administered as a sublingual oil, oral capsule, or soft gel – against a placebo, while the ninth used amitriptyline as an active comparator. Dosing schedules, intervention lengths, and follow-up periods varied significantly. Five of the nine studies were conducted in Australia, two were conducted in the United States, and one each in Canada and Thailand.
There was very low-certainty evidence from seven studies of 374 participants that medical cannabis had little to no clinically meaningful effect of the quality of sleep or sleep satisfaction (as determined by measures such as the Insomnia Severity Index and the Pittsburgh Sleep Quality Index). The standardised mean difference between medical cannabis and placebo was -0.49 (95% confidence interval -1.06 to 0.08), suggesting a slight but non-significant benefit of medical cannabis.
Similarly, there was very low-certainty evidence from six studies of 194 participants that medical cannabis may have little to no clinically meaningful effect on total sleep time (mean difference from placebo 7.68 minutes, 95% CI -23.04 to 38.39 minutes).
Fewer studies reported other sleep-related outcomes such as sleep onset latency and wake after sleep onset (four studies, 109 participants for both measures). There were too few studies to comment on the quality of the evidence for these measures, but the potential effect of medical cannabis relative to placebo seemed small. The pooled mean difference in sleep onset latency was -4.30 minutes (95% CI -26.82 to 18.22 minutes), and -2.79 minutes (95% CI -34.40 to 28.82 minutes) for wake after sleep onset.
There was very low-certainty evidence that medical cannabis may lead to little to no clinically significant difference in daytime functioning (as measured by tools such as the Epworth Sleepiness Scale, the Stanford Sleepiness Scale, or the E Digit Symbol Substitution Task). The standardised mean difference was -0.34 (95% CI -0.83 to 0.16) across five studies with 144 participants.
Things were no better for the lone study comparing medical cannabis to amitriptyline.
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“This study reported a mean difference of -3.25 with a 95% CI -5.17 to -1.33 for quality of sleep/satisfaction with sleep using the Insomnia Severity Index… and an MD of 0.7 and 95% CI -5.56 to 6.96 for quality of life using the Fibromyalgia Impact Questionnaire,” the researchers said. “It also reported adverse events, with one event in the medical cannabis group and two events in the amitriptyline group (RR 0.5, 95% CI 0.05 to 5.24).”
Six studies reported adverse events, but only three (involving 98 participants) were included in the current synthesis. There was low-certainty evidence that medical cannabis may be associated with an increase in adverse events compared to placebo (odds ratio 11.25, 95% CI 4.46 to 28.35).
Five of the studies comparing medical cannabis against a placebo were deemed to have a high risk of bias. A further two studies had some concerns regarding the potential for bias.
“The studies with high risk of bias or some concerns risk of bias mainly arose from bias in the selection of reported results… missing outcome data… deviations from intended interventions… and bias from the randomisation process,” the researchers said.
A key limitation of the included studies was the fact that they were all conducted in middle- and high-income countries, meaning it is unclear whether the findings of the current Cochrane review would apply to low-resource settings. In addition, few studies included (older) participants with comorbidities, which further limits the generalisability of the findings.
Dr Luis Garegnani, an epidemiologist and medical researcher from the Universidad Hospital Italiano de Buenos Aires, Argentina, who served as the senior author on the current review, encouraged both clinicians and patients to wait for the findings of higher-quality research.
“Rather than viewing the findings as either an endorsement or a rejection of medical cannabis, clinicians and patients should recognise the uncertainty and consider individual circumstances while better evidence is generated,” he said in a statement.
The researchers identified five studies investigating the effects of medical cannabis versus placebo that were ongoing at the time of their literature search (April 2025). The findings from these studies may be included in future reviews.
