Cannabis Use Does Not Outperform Placebo in Improving Parkinson Disease Symptoms

Short-term use of daily cannabis (cannabidiol [CBD]/low delta-9-tetrahydrocannabinol [THC]) is tolerated by patients with Parkinson disease (PD) but does not outperform placebo for motor symptom improvement, according to new research presented at the Future of Parkinson’s Disease Conference held from November 30 to December 3, 2023 in Austin, Texas.

While cannabis use is common among patients with PD, little evidence exists regarding the safety and efficacy outcomes of CBD/THC in this population. The current study aimed to examine CBD/THC tolerability and its impact on motor and nonmotor symptoms among patients with PD.

Patients with PD who were not currently using cannabis and who scored 20 or greater on the motor Movement Disorder Society Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) took an oral solution of CBD/THC daily for 2 weeks, increasing to a final dose of 2.5mg/kg/day. The primary outcome of interest for investigators was the change in motor MDS-UPDRS from baseline to final dose. Additionally, secondary outcomes included tolerability and other motor and nonmotor symptoms.

The investigators included a total of 61 patients in the study and randomly assigned 31 to CBD/THC and 30 to placebo. The mean final dose consisted of 191.8 mg (SD, 48.9) CBD and 6.4 mg (SD, 1.6) THC daily. Among the cannabis cohort, motor MDS-UPDRS was reduced by 4.57 (95% CI, -8.11 to -1.03; P =.013) while the placebo group reported a reduction of 2.77 (95% CI, -4.92 to -0.61; P =.014). Thus, the reduction in reported motor symptoms was not statistically different between the groups (-1.80; 95% CI, -5.88 to 2.27; P =.379). Furthermore, placebo was favored over cannabis for sleep, cognition, and activities of daily life.

Adverse events (AEs) were mild overall but did occur twice as often in the CBD/THC group relative to the placebo group. Frequently reported AEs consisted of dizziness (58% vs 20%), feelings of relaxation (42% vs 23%), fatigue (32% vs 20%), decreased concentration (32% vs 13%), headache (29% vs 33%), and somnolence (26% vs 26%) for the cannabis and placebo cohorts, respectively. In the CBD/THC group, 1 serious AE occurred and 1 patient withdrew due to intolerance.

These results indicate that cannabis use, even in the short term, may not be beneficial for patients with PD and could potentially even worsen cognition and sleep. “Longer-term controlled trials that monitor cannabinoid concentrations are essential and would require improved availability of research cannabinoid products,” the investigators concluded.

This article originally appeared on Psychiatry Advisor