CBD/THC extract showed no clear benefit for Parkinson's motor symptoms in a short trial, and may have worsened sleep and cognition | Research

The takeaway

A two-week RCT of 61 Parkinson's patients found that a high-CBD/low-THC cannabis extract did not significantly improve motor symptoms compared to placebo, and may have worsened cognition and sleep.

Parkinson's patients considering cannabis, neurologists, and movement disorder specialists.

No significant motor benefit vs. placebo (p = 0.379)

What the researchers found

Motor scores improved in both the CBD/THC group (4.57-point reduction) and placebo group (2.77-point reduction), but the between-group difference was not statistically significant (p = 0.379). Sleep, cognition, and daily living assessments showed effects favoring placebo.

Why it matters

Cannabis use is common among Parkinson's patients despite limited evidence. This trial provides some of the first rigorous data, and the results suggest high-CBD/low-THC formulations may not help motor symptoms and could have downsides.

The numbers in context

61 participants randomized. Mean final dose: 191.8 mg CBD + 6.4 mg THC daily. Motor improvement: 4.57 points (CBD/THC) vs. 2.77 points (placebo), difference not significant (p = 0.379). CBD plasma level at final dose: 54.0 ng/mL.

How the study worked

Double-blind RCT of 61 participants with Parkinson's disease randomized to CBD/THC oral solution (n=31) or placebo (n=30) for two weeks. Final dose averaged 192 mg CBD and 6.4 mg THC daily. Used MDS-UPDRS motor scores as the primary outcome.

What this study cannot tell us

Only two weeks long, which may be too short to detect meaningful effects. Strong placebo response. Relatively small sample. The authors note that longer, larger trials with better research cannabis products are needed.

How to read the evidence

Well-designed double-blind RCT with plasma monitoring, but limited by short duration and strong placebo response.

When this study was published

2024 publication of a two-week trial.

The bigger picture

The strong placebo response in this trial mirrors a pattern seen across Parkinson's research, making it harder to detect real treatment effects. The absence of benefit, combined with possible cognitive and sleep harms, challenges popular assumptions about cannabis for Parkinson's.

Questions still open

Would a longer trial with higher THC ratios produce different results? Are certain Parkinson's symptoms (like pain or anxiety) more responsive to cannabis than motor symptoms?

Common questions

Did cannabis help Parkinson's motor symptoms?

Both groups improved, but the difference between CBD/THC and placebo was not statistically significant. The placebo response was strong.

Were there any negative effects?

Sleep, cognition, and activities of daily living scores favored placebo, suggesting the CBD/THC extract may have worsened these areas. Adverse events were generally mild but more common in the treatment group.

What dose was used?

Participants worked up to about 192 mg CBD and 6.4 mg THC daily over two weeks, taken as an oral sesame oil solution.

Read the original research

Short-Term Cannabidiol with Δ-9-Tetrahydrocannabinol in Parkinson's Disease: A Randomized Trial.

Movement disorders : official journal of the Movement Disorder Society, 39(5), 863-875

View on PubMed ↗Publisher’s paper ↗

Citation

Liu, Ying; Bainbridge, Jacquelyn; Sillau, Stefan; Rajkovic, Sarah; Adkins, Michelle; Domen, Christopher H; Thompson, John A; Seawalt, Tristan; Klawitter, Jost; Sempio, Cristina; Chin, Grace; Forman, Lisa; Fullard, Michelle; Hawkins, Trevor; Seeberger, Lauren; Newman, Heike; Vu, David; Leehey, Maureen Anne. (2024). Short-Term Cannabidiol with Δ-9-Tetrahydrocannabinol in Parkinson's Disease: A Randomized Trial.. Movement disorders : official journal of the Movement Disorder Society, 39(5), 863-875. https://doi.org/10.1002/mds.29768