A three-armed RCT comparing inhaled THC + CBD oil, CBD oil alone, and placebo for endometriosis pain recruited only 12 of 63 intended participants, with most dropping out due to driving restrictions.
Clinical trial designers, endometriosis researchers, medical cannabis advocates
Only 4 of 63 target participants completed the trial due to driving restrictions
What the researchers found
Only 12 of 63 target participants enrolled; 7 withdrew and only 4 completed; the primary barrier was the requirement to abstain from driving during THC treatment; high withdrawal rate made efficacy assessment impossible.
Why it matters
Despite strong patient interest in cannabis for endometriosis, practical barriers like driving restrictions make clinical trials nearly impossible, leaving a major evidence gap.
The numbers in context
12 of 63 target enrolled; 7 withdrew; 4 completed; 1 lost to follow-up; 10 adverse events (8 possibly cannabis-related); 2 serious adverse events (unrelated).
How the study worked
Three-armed RCT in Australia comparing inhaled THC (16%) flower + CBD oil (100mg/mL), CBD oil alone, or placebo oil; aimed for 63 participants; assessed safety, acceptability, and feasibility.
What this study cannot tell us
Failed to achieve recruitment target; cannot assess efficacy; Australian regulatory context; small enrolled sample prevents meaningful safety conclusions.
How to read the evidence
Feasibility RCT that failed its primary goal; valuable as a cautionary report for future trial design.
When this study was published
Published 2025
The bigger picture
The tension between cannabis clinical research and real-world constraints represents a systemic barrier to generating the evidence base that patients and clinicians need.
Questions still open
- Can future trials use designs that accommodate driving needs? Would evening-only dosing or CBD-only arms improve recruitment? How can cannabis research overcome practical barriers?
Common questions
Why did the trial fail?
Is there evidence cannabis helps endometriosis?
Read the original research
Challenges in conducting a feasibility randomized controlled trial of medicinal cannabis for endometriosis pain in Australia.
Complementary therapies in clinical practice, 61, 102023
Citation
Chesterman, Susan; Mikocka-Walus, Antonina; Sinclair, Justin; Druitt, Marilla; Furyk, Jeremy; Evans, Subhadra; Abbott, Jason; Eathorne, Alexandra; Martin, Alexander; Ng, Cecilia; Nguyen, Lisa; Oldfield, Karen; Romano, Daniel; Sarris, Jerome; Semprini, Alex; Stanley, Katherine; Armour, Mike. (2025). Challenges in conducting a feasibility randomized controlled trial of medicinal cannabis for endometriosis pain in Australia.. Complementary therapies in clinical practice, 61, 102023. https://doi.org/10.1016/j.ctcp.2025.102023
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