Cognitive Safety Data from a Randomized, Double‐Blind, Parallel‐Group, Placebo‐Controlled Phase IIb Study of the Effects of a Cannabidiol and Δ9‐Tetrahydrocannabinol Drug on Parkinson's Disease‐Related Motor Symptoms

Background Cannabis is increasingly available worldwide but its impact on cognition in Parkinson's disease (PD) is unknown. Objective Present cognitive safety data from study of an oral high‐dose cannabidiol (CBD; 100 mg) and low‐dose Δ9‐tetrahydocannabinol (THC; 3.3 mg) drug in PD. Methods Randomized, double‐blind, parallel‐group, placebo‐controlled study of a CBD/THC drug administered for 16.3 (SD: 4.2) days, with dosage escalating to twice per day. Neuropsychological tests were administered at baseline and 1–1½ hours after final dose; scores were analyzed with longitudinal regression models (alpha = 0.05). Cognitive adverse events were collected. Results When adjusted for age and education, the CBD/THC group (n = 29) performed worse than the placebo group (n = 29) on Animal Verbal Fluency. Adverse cognitive events were reported at least twice as often by the CBD/THC than the placebo group. Conclusion Data suggest this CBD/THC drug has a small detrimental effect on cognition following acute/short‐term use in PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.