A Cochrane review by researchers from the University of Manitoba and Universidad Hospital Italiano de Buenos Aires examined nine clinical trials involving 537 adults with insomnia. Eight trials compared medical cannabis to placebo, while one compared it to amitriptyline, an antidepressant used for sleep problems.
Across the placebo comparisons, medical cannabis produced little or no clinically meaningful improvement in sleep quality, satisfaction with sleep, total hours slept, or daytime functioning. Participants receiving medical cannabis were substantially more likely to experience mild side effects like dizziness and dry mouth compared to those given placebo.
The reviewers rated their confidence in the available evidence as low or very low, citing small study populations, conflicting findings, and potential bias in trial conduct. Studies tested different cannabis products, making direct comparisons difficult. The longest trial lasted just 12 weeks, leaving questions about lasting benefits. Women accounted for 72.66% of participants, and research focused on younger adults, leaving unclear whether findings apply to men, older people, or those with insomnia linked to other medical conditions.
"The main message is that the research currently available is not sufficient to reliably answer whether medical cannabis helps people with insomnia," Dr. Lucia Varela, lead author, said. "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. Luis Garegnani, senior author, added that larger, more rigorous clinical trials are needed before cannabis can be confidently recommended for sleep improvement.