Cannabidiol and cognition: a literature review of human randomized controlled trials

Cannabidiol (CBD) is a phytocannabinoid without intoxicating properties. While CBD can improve neurophysiological functions and subjective symptoms, its effect on cognitive function remains unclear. We summarized the available randomized controlled trials investigating CBD administration and cognitive function. A review of the literature was conducted using the following keywords on PubMed/Medline: (cannabis OR cannabidiol OR cannabinoid OR CBD OR Δ 9 -tetrahydrocannabinol OR tetrahydrocannabinol) AND (neurology OR brain OR psychiatric OR neuroscience OR psychology OR cognition) AND (human) AND (randomized controlled trial OR RCT). The search yielded 1038 articles with 36 total included for this literature review. The articles included healthy participants, neurological disease, psychiatric disease, psychosis, paranoia, schizophrenia, and drug-use disorders. Studies with healthy participants included a variety of dosing strategies, suggesting an effect on cognitive function and sleep quality. In Parkinson's disease, 75-300 mg CBD resulted in mild improvements in daily life activities. Decreases in subjective anxiety were found in patients with psychiatric disease using CBD doses ranging from 300 to 400 mg. In patients with psychosis and paranoia, 600 mg CBD showed inconsistent results in cognitive function. In patients with schizophrenia, up to 1000 mg CBD per day had minimal effects on cognition. Finally, up to 800 mg CBD had minimal effects on cognitive function in patients with substance use disorders. The findings are limited by utilization of acute dosing, variations in CBD dose, and different routes of administration. Standardized dosing and CBD formulations are needed to assess its efficacy for improving cognition.