Long-term safety of medical cannabis in Parkinson's disease: A retrospective case-control study

Background: Whole-plant medical cannabis (MC) products are widely used for controlling symptoms associated with Parkinson’s disease (PD). Despite its widespread use, few studies have investigated the long-term impact of MC on the progression of PD or its safety profile. This study examined the effects of MC on PD in a real-life setting.

Methods: A retrospective case-control study of 152 idiopathic PD patients (mean age 69.1 ± 9.0 years), followed at the Sheba Medical Center Movement Disorders Institute (SMDI) from 2008 to 2022 was conducted. Seventy-six patients who used licensed whole-plant medical cannabis (MC) for at least a year were compared to a matched group who did not receive MC in terms of their Levodopa Equivalent Daily Dose (LEDD), Hoehn and Yahr (H&Y) stage, and cognitive, depressive, and psychotic symptoms.

Results: The median monthly dose of MC was 20 g (IQR: 20-30), with a median Tetrahydrocannabinol (THC) percentage of 10 (IQR: 9.5-14.15) and a median Cannabidiol (CBD) percentage of 4 (IQR: 2-10). There were no significant differences between the MC and the control groups for LEDD or H&Y stage progression (p = 0.90, 0.77, respectively). A Kaplan-Meier analysis showed no evidence of relative worsening of psychotic, depressive, or cognitive symptoms reported by patients to their treating physicians over time in the MC group (p = 0.16-0.50).

Conclusion: Over the 1-3 years of follow-ups, the MC treatment regimens appeared to be safe. MC did not exacerbate neuropsychiatric symptoms and had no detrimental effects on disease progression.