Duration of Neurocognitive Impairment With Medical Cannabis Use: A Scoping Review
While the recreational use of cannabis has well-established dose-dependent effects on neurocognitive and psychomotor functioning, there is little consensus on the degree and duration of impairment typically seen with medical marijuana use. Compared to recreational cannabis users, medical cannabis patients have distinct characteristics that may modify the presence and extent of impairment. The goal of this review was to determine the duration of acute neurocognitive impairment associated with medical cannabis use, and to identify differences between medical cannabis patients and recreational users. These findings are used to gain insight on how medical professionals can best advise medical cannabis patients with regards to automobile driving or safety-sensitive tasks at work. A systematic electronic search for English language randomized controlled trials (RCTs), clinical trials and systematic reviews (in order to capture any potentially missed RCTs) between 2000 and 2019 was conducted through Ovid MEDLINE and EMBASE electronic databases using MeSH terms. Articles were limited to medical cannabis patients using cannabis for chronic non-cancer pain or spasticity. After screening titles and abstracts, 37 relevant studies were subjected to full-text review. Overall, seven controlled trials met the inclusion/exclusion criteria and were included in the qualitative synthesis: six RCTs and one observational clinical trial. Neurocognitive testing varied significantly between all studies, including the specific tests administered and the timing of assessments post-cannabis consumption. In general, cognitive performance declined mostly in a THC dose-dependent manner, with steady resolution of impairment in the hours following THC administration. Doses of THC were lower than those typically reported in recreational cannabis studies. In all the studies, there was no difference between any of the THC groups and placebo on any neurocognitive measure after 4 h of recovery. Variability in the dose-dependent relationship raises the consideration that there are other important factors contributing to the duration of neurocognitive impairment besides the dose of THC ingested. These modifiable and non-modifiable factors are individually discussed.
Keywords: cannabidiol; cannabinoids; cognition; impairment; intoxication; medical cannabis; pain; tetrahydrocannabinol.
Copyright © 2021 Eadie, Lo, Christiansen, Brubacher, Barr, Panenka and MacCallum.
Conflict of interest statement
CM has received support for industry sponsored continuing medical education from Canopy, Medreleaf, Doja, Compass Cannabis Clinics. She has been on the scientific advisory board of Emerald Health Therapeutics, Shoppers Drug Mart, Strainprint and Resolve. She is the Medical Director of Greenleaf medical clinic, Vitality and Translational Life Sciences. She is on the Board of Directors for The Green Organic Dutchman. WP is the founder and CEO of Translational Life Sciences, an early stage science company focused on cannabinoid therapeutics. He has also been on the scientific advisory board of Medipure Pharmaceuticals and Vitality Biopharma, and in the past has been on the board of directors for Abbatis bioceuticals and on the advisory board of Vinergy Resources. AB has been a scientific advisor to Emerald Health Therapeutics, Cannevert Therapeutics, Global Cannabis Applications Corp, Medipure Pharmaceuticals, Vitality Biopharma and Hai Beverages. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.