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

Abstract

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.