Cannabinoids, including the two main phytocannabinoids Δ-tetrahydrocannabinol (THC) and cannabidiol (CBD), are being increasingly utilised as pharmacological interventions for sleep disorders. THC and CBD are known to interact with the endocannabinoid and other neurochemical systems to influence anxiety, mood, autonomic function, and circadian sleep/wake cycle. However, their therapeutic efficacy and safety as treatments for sleep disorders are unclear. The current systematic review assessed the available evidence base using PubMed, Scopus, Web of Science, Embase, CINAHL and PsycInfo databases. A total of 14 preclinical studies and 12 clinical studies met inclusion criteria. Results indicated that there is insufficient evidence to support routine clinical use of cannabinoid therapies for the treatment of any sleep disorder given the lack of published research and the moderate-to-high risk of bias identified within the majority of preclinical and clinical studies completed to-date. Promising preliminary evidence provides the rationale for future randomised controlled trials of cannabinoid therapies in individuals with sleep apnea, insomnia, post-traumatic stress disorder-related nightmares, restless legs syndrome, rapid eye movement sleep behaviour disorder, and narcolepsy. There is a clear need for further investigations on the safety and efficacy of cannabinoid therapies for treating sleep disorders using larger, rigorously controlled, longer-term trials.
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