Low-Dose CBD Was Safe for Parkinson's Patients but Showed Limited Cognitive Benefit
A 12-week randomized trial found 26 mg/day sublingual CBD was safe in Parkinson's disease but did not significantly improve memory or motor symptoms, with only naming scores showing improvement.
Quick Facts
What This Study Found
Among 51 Parkinson's patients completing the trial, low-dose CBD (26 mg/day) was safe with no serious side effects. The only significant cognitive improvement was in MoCA naming scores. Delayed recall (primary outcome), language, inflammatory markers, and motor symptoms showed no differences between CBD and placebo groups.
Key Numbers
60 randomized (27 CBD, 24 placebo completed). Mean CBD dose: 26 mg/day, THC: 1.2 mg/day. CBD detected in serum at mean 2 ng/mL. No THC detected. Only naming score improved (mean difference: 0.37, 95% CI: 0.01-0.73).
How They Did This
Double-blind randomized controlled trial of 60 Parkinson's patients (51 completed) comparing 12 weeks of sublingual CBD-enriched product (101.9 mg/mL CBD, 4.8 mg/mL THC) to placebo, measuring cognitive, motor, and inflammatory outcomes.
Why This Research Matters
This is one of the few rigorous RCTs testing CBD in Parkinson's disease. While the results are largely negative at this dose, the safety data supports exploration of higher doses in future trials.
The Bigger Picture
The Parkinson's community has enormous interest in CBD, but this trial suggests very low doses may not be sufficient. The safety profile is encouraging for future dose-escalation studies.
What This Study Doesn't Tell Us
Very low CBD dose (26 mg/day) may be below therapeutic threshold. Small sample after dropout. 12-week duration may be too short. Blood levels suggest poor bioavailability. CBD-enriched product contained trace THC.
Questions This Raises
- ?Would higher CBD doses produce meaningful cognitive benefits?
- ?Is sublingual the optimal route for Parkinson's patients?
- ?How long would treatment need to continue for effects to emerge?
Trust & Context
- Key Stat:
- 26 mg/day CBD safe in Parkinson's but largely ineffective at this low dose
- Evidence Grade:
- Rigorous double-blind RCT, but small sample, high dropout, and very low dose limit ability to draw definitive conclusions about CBD efficacy.
- Study Age:
- 2025 randomized controlled trial from Buriram Hospital, Thailand.
- Original Title:
- Cannabidiol and cognitive functions/inflammatory markers in Parkinson's disease: A double-blind randomized controlled trial at Buriram Hospital (CBD-PD-BRH trial).
- Published In:
- Parkinsonism & related disorders, 135, 107841 (2025)
- Authors:
- Mitarnun, Witoon, Kanjanarangsichai, Auempa, Junlaor, Panomporn, Kongngern, Lisa, Mitarnun, Wenika, Pangwong, Wilasinee, Nonghan, Pawarin
- Database ID:
- RTHC-07156
Evidence Hierarchy
Participants are randomly assigned to treatment or placebo groups to test cause and effect.
What do these levels mean? →Frequently Asked Questions
Does CBD help with Parkinson's disease?
At the very low dose tested (26 mg/day), CBD did not significantly improve memory, motor symptoms, or inflammation in this 12-week trial. Only naming ability showed modest improvement. Higher doses may be needed.
Is CBD safe for Parkinson's patients?
In this trial, CBD at 26 mg/day for 12 weeks was safe with no serious adverse effects and no worsening of motor, cognitive, or mood symptoms. The only lab change was mildly elevated alkaline phosphatase.
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Cite This Study
https://rethinkthc.com/research/RTHC-07156APA
Mitarnun, Witoon; Kanjanarangsichai, Auempa; Junlaor, Panomporn; Kongngern, Lisa; Mitarnun, Wenika; Pangwong, Wilasinee; Nonghan, Pawarin. (2025). Cannabidiol and cognitive functions/inflammatory markers in Parkinson's disease: A double-blind randomized controlled trial at Buriram Hospital (CBD-PD-BRH trial).. Parkinsonism & related disorders, 135, 107841. https://doi.org/10.1016/j.parkreldis.2025.107841
MLA
Mitarnun, Witoon, et al. "Cannabidiol and cognitive functions/inflammatory markers in Parkinson's disease: A double-blind randomized controlled trial at Buriram Hospital (CBD-PD-BRH trial).." Parkinsonism & related disorders, 2025. https://doi.org/10.1016/j.parkreldis.2025.107841
RethinkTHC
RethinkTHC Research Database. "Cannabidiol and cognitive functions/inflammatory markers in ..." RTHC-07156. Retrieved from https://rethinkthc.com/research/mitarnun-2025-cannabidiol-and-cognitive-functionsinflammatory
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.