CBD and endometriosis: what the placebo trial showed

In endometriosis, a chronic disease, tissue resembling the lining of the uterus grows outside it, on the ovaries, the fallopian tubes or the peritoneum. The Inserm dossier puts the share of women concerned at about 10%. First-line treatment is hormonal, and surgery removes the lesions.

Interest in CBD comes from two observations. One is biological: CBD acts on some of the pathways involved in the disease, among them the endocannabinoid system, a network of receptors involved in pain. The other comes from patients, some of whom say they use cannabis. A review published in late 2024 in Trends in Pharmacological Sciences brings together data on these pathways from patient samples and animal models. An Edinburgh team wrote it, with a co-author from the company MRX Medical. Such plausibility is a reason to run trials and proves nothing about efficacy in women.

The Ribeirão Preto Medical School of the University of São Paulo ran the DREAMLAND trial, published in Cannabis and Cannabinoid Research. The protocol was as follows:

In each group, pain dropped by at least 50% for about 40% of participants and by at least 30% for about 60%. Mean pain at the end of treatment stood at 41.6 mm on CBD and 36.8 mm on placebo. Both groups clearly improved, and the gap between them was not significant.

The trial was stopped at the interim analysis set out in the protocol: the primary outcome showed no difference, and side effects were more frequent on CBD. They were mild, mostly digestive, along with perceived weight changes, and none was serious. Scores on some psychological symptoms and quality-of-life domains favoured the CBD group, while the placebo group did better on the physical domains. The authors conclude that CBD was not superior to placebo.

On placebo, six participants in ten had their pain fall by at least 30%. Had there been no control group, the product would have been credited with that improvement. The data most often shared have exactly this weakness.

An Australian online survey published in 2020 gathered 484 responses from women whose endometriosis had been confirmed surgically. Of those using some form of self-management, 13% used cannabis. They scored its effect on pain at 7.6 out of 10, and 56% reported cutting their medicines by at least half. The figures are self-reported. Respondents came through patient groups on social media, the product was cannabis, so CBD was never studied alone, and no group received a placebo.

The hierarchy of evidence, from animal model to survey, open-label trial and placebo-controlled trial, is set out in our article on what CBD clinical studies say.

On 23 September 2026, the ClinicalTrials.gov registry listed five studies on cannabidiol and endometriosis. Two have stopped: DREAMLAND, and a US trial started in December 2020 after 12 participants. Two US studies are recruiting, aiming for 30 and 60 participants. The status of a Spanish study of 10 participants, testing a THC and CBD combination, is no longer up to date.

In the United Kingdom, the University of Edinburgh is preparing the ENDOCAN-1 trial, with 100 participants and a CBD medicine called MRX-1. Recruitment was announced for April 2026 in the Scottish health boards of Lothian and Grampian. This feasibility study is designed to find the dose and will not yet prove efficacy; its authors see it as groundwork for a larger trial.

Speak to your doctor or gynaecologist first, and do not stop a prescribed treatment on your own. Shop CBD is not a medicine and cannot replace diagnosis or follow-up.

The European Food Safety Authority set a provisional level of 0.0275 mg per kilo of body weight per day on 9 February 2026. That comes to about 2 mg a day for an adult of 70 kg. In its view, the safety of CBD cannot be established for pregnant or breastfeeding women, people under 25 or people on medication. Many patients on hormonal therapy fall into that last group. The calculation is detailed in our article on the EFSA reference dose.

Raise three points at your appointment:

• interactions: CBD slows some of the liver enzymes that clear many medicines, as explained in our articles on the grapefruit effect and on CBD and the liver;
• pregnancy plans, frequent among patients: ANSES proposed on 21 March 2025 classifying CBD as presumed toxic to reproduction, a subject covered in our article on CBD during pregnancy and breastfeeding;
• how it is taken: CBD products to be swallowed come under the novel food regime, as our overview of CBD regulation in 2026 describes.

Epidyolex, the only authorised cannabidiol medicine, is prescribed for certain rare epilepsies; endometriosis is not among its indications.