High-potency cannabis still lacks solid evidence of safety and efficacy

Higher delta-9-tetrahydrocannabinol (THC) concentration medicinal cannabis products are characterised by a higher THC and minimal cannabidiol (CBD) content. This rapid review aims to systematically summarise and evaluate the available evidence regarding the efficacy and safety of higher THC potency medicinal cannabis products relevant to the Australian market in adult populations. The rapid literature review protocol was prospectively registered with Open Science Framework: https://doi.org/10.17605/OSF.IO/HNFUT. The comprehensive search (1-January-2014-30-July-2024) included Medline, EMBASE, EMCARE, CINAHL, SCOPUS and the Cochrane Central Register of Controlled Trials databases. Eligible studies (randomised controlled trials and observational studies) were screened by two independent reviewers and then extracted. We identified 9969 records, resulting in 15 studies (six RCTs and nine observational), with THC concentrations of 16%-22% that met inclusion criteria. Studies examining efficacy for pain (n = 4), ulcerative colitis (n = 1) and chronic obstructive pulmonary disease (n = 1) reported mixed outcomes. Reported adverse events included psychiatric, nervous system and gastrointestinal effects. Validated cannabis use disorder (CUD) screening tools were notably absent from the included studies. Few studies have assessed products equivalent to the Australian Category 5 medicinal cannabis product definition, with most having THC concentrations lower than those available for prescription in Australia, including products reported to contain up to 88% THC. High-quality RCTs and longitudinal studies that incorporate validated CUD screening tools are needed. No evidence was found on safety or efficacy of prescribed Category 5 medicinal cannabis products with THC concentrations above 22% w/w (220 mg/g).