For many women with endometriosis, the month splits into two kinds of days: days with pain, and days spent waiting for it. The women who joined a small study at Berlin’s Charité university hospital had already worked through the standard toolbox — hormone therapy, surgery, ibuprofen and diclofenac, and in some cases opioids — and were still reaching for painkillers on most days of the month. So the researchers added one more thing to their existing treatment: a measured dose of a standardized cannabis extract, taken by mouth twice a day, for three months.
The results were published on 22 September 2026 in PLOS One by a team from the Endometriosis Research Centre Charité, with gynecologist Sylvia Mechsner as senior author. They point to lower pain, fewer days on painkillers and a better quality of life. They also come with caveats that matter just as much: only 27 women completed the study, there was no placebo group, and every participant knew exactly what she was taking.
Key Takeaways
In this prospective pilot study, 30 premenopausal women with confirmed endometriosis and pain that had not responded to hormonal and pain medication were given an oral cannabis extract with a balanced ratio of THC to CBD on top of their usual treatment, and 27 of them completed three months. After a four-week build-up, the typical daily dose settled at about 10 mg of THC and 12 mg of CBD and did not creep upward over time. Average pain on a 0–10 scale fell from 6.81 at baseline to 5.15 after one month, 4.59 after two months and 4.93 after three, the number of days needing painkillers dropped significantly, and scores for fatigue, anxiety, pain-related disability and every domain of an endometriosis-specific quality-of-life questionnaire improved. Side effects were mostly mild, but nearly every participant reported at least one, and tiredness plus concentration and memory complaints affected around 60% throughout. Because the study was small, unblinded, run at a single center and lacked a comparison group, it shows that this approach is feasible and worth testing properly — not that it works.
Inside the Cannabinoid Extract Endometriosis Pain Study: Who Took Part
Endometriosis is a condition in which tissue similar to the lining of the womb grows outside it, mostly inside the pelvis. That tissue reacts to hormones and triggers inflammation, which can mean severe period pain, pain during sex, chronic pelvic pain and fertility problems. The authors note that it affects roughly 10% of women of reproductive age worldwide.
The pain is not only about inflammation at the site of the lesions. Over time, the nervous system itself can become oversensitive — a process called central sensitization. A useful comparison is a smoke alarm whose sensitivity has been turned up so high that it goes off when someone makes toast. The signal is real, but the system amplifies it. This matters for the study, because it is one reason why standard painkillers often fall short.
Between 1 November 2023 and 31 May 2025, the Charité team enrolled 30 women. To qualify, participants needed a confirmed endometriosis diagnosis, chronic pelvic pain that was not tied to the menstrual cycle for at least three months, an average pain score of at least 4 out of 10, and a separate clinical indication for cannabis-based medicine documented by a Charité physician. Women with heart disease, known addiction disorders, regular cannabis use in the previous six months, or who were pregnant, breastfeeding or planning a pregnancy were excluded. Nobody was allowed to start or change hormonal therapy in the three months before or during the study, so that any change could not simply be put down to new hormones.
One woman dropped out during the build-up phase because of side effects, and two stopped returning questionnaires. That left 27 participants with an average age of 32.9 years. Most (81.5%) were already on hormone therapy. Just over half (51.9%) had the mildest surgical stage of the disease, rASRM stage I — a reminder that in endometriosis, how the lesions look during surgery says little about how much pain a woman feels. On average, participants had undergone 1.9 operations.
The baseline picture was one of pain that ordinary treatment was not controlling. In the month before the study, average pain intensity was 6.8 out of 10. Almost everyone had used anti-inflammatory painkillers, many also used paracetamol and metamizole, and seven women were actively taking opioids such as tramadol, tilidine or oxycodone when the study began. Twelve had never used opioids. Cannabis experience was limited: 37.0% had never used it, 44.4% had tried it only in the distant past, and none used it regularly.
The Dose: What the Participants Actually Took
All participants received an oral cannabinoid-based medicinal product classified as chemotype 2, meaning it contains THC and CBD in roughly equal amounts. The extract contained 12 mg of THC and 14 mg of CBD per millilitre. Rather than starting at full strength, the team raised the dose slowly over four weeks to limit side effects, and called each participant by phone after two and four weeks to check how she was coping.
After this build-up, the target was about 10 mg of THC and 12 mg of CBD per day, split into two doses: 0.3 ml in the morning (3.6 mg THC and 4.2 mg CBD) and 0.5 ml in the evening (6.0 mg THC and 7.0 mg CBD). Over the three months, the median doses stayed at exactly those levels. The authors read this as a sign that the effect did not fade and that participants did not need more and more of the extract to get the same relief — although three months is too short to say anything about the longer term.
The extract was supplied by the cannabis company Khiron and dispensed through Bezirks Apotheken, which the authors acknowledge in the paper. The study received no specific funding, and the authors declared no competing interests. These figures describe a supervised research protocol, not a guide for anyone to follow on their own.
What Happened to Pain and Painkiller Use
Pain intensity fell early and stayed lower. Compared with a baseline score of 6.81, the average was 5.15 after the first month, 4.59 after the second and 4.93 after the third. Each of these differences was statistically significant, meaning they were unlikely to be a fluke of chance within this group.
The number of days with pain also went down. According to the results section, the median fell from 30 days per month at baseline to 20 after two months and 17 after three. Readers checking the paper should note that its baseline table reports the painkiller and pain-day measures differently — a median of 30 days on painkillers and 13 days in pain despite them — so the exact starting value for each measure is not fully clear from the published text.
The days on which women needed painkillers dropped significantly, with a measurable change already after the first month. Because some participants were on anti-inflammatory drugs and seven were on opioids, the authors describe the extract as potentially “opioid-sparing” and “NSAID-sparing”. That is an interpretation rather than a separate finding: the paper does not report how many of the seven women taking opioids reduced or stopped them. It is still a relevant question. A Cochrane review of anti-inflammatory painkillers for endometriosis found little solid evidence that they work well for this pain, and long-term opioid use carries well-known risks. Similar opioid-reduction signals have appeared in an Australian study of chronic pain patients prescribed medical cannabis, though in a very different patient group.
One smaller observation deserves attention. Women on hormone therapy and those not on it reported the same pain intensity, but hormone users reported more days of pain per month. The difference did not reach statistical significance and the groups were unequal in size, so the authors treat it as a hint rather than a result.
Beyond Pain: Fatigue, Anxiety and Quality of Life
Endometriosis is increasingly seen as a whole-body condition, and the study measured more than pain. After three months, fatigue scores improved, as did anxiety measured with a standard seven-question screening tool. Scores on the Central Sensitization Inventory — a questionnaire estimating how much the nervous system is amplifying pain — also dropped, and so did the Pain Disability Index, which asks how much pain interferes with work, social life and daily activities.
Interestingly, improvements in central sensitization tracked only moderately with improvements in day-to-day pain scores. In plain terms, the two did not simply move as one, which the authors take as a sign that the extract may be acting on how the nervous system processes pain, not just on how much pain is felt at a given moment. This is a hypothesis, not something this design can prove.
The study’s main goal was defined in advance: a 15-point improvement in the pain section of the Endometriosis Health Profile-30 (EHP-30), a questionnaire where scores run from 0 (best health) to 100 (worst). The pain score fell from 59.34 to 38.38 — a larger drop than the target. Every other section improved too. Feelings of control and powerlessness went from 72.76 to 43.52, emotional well-being from 52.01 to 34.26, self-image from 58.33 to 37.04, social support from 53.94 to 40.51, work-related impairment from 51.67 to 34.81, and sexual relationships from 54.26 to 40.19.
Side Effects: Mostly Mild, But Almost Universal
The extract was described as well tolerated, but that should not be read as side-effect-free. Nearly all participants reported at least one side effect, whatever their dose. Fatigue, concentration and memory problems were the most persistent, affecting around 60% of women throughout the three months.
Other effects faded with time. Anxiety or panic fell from 26% to 4%, and paranoia from 4% to 0%. Nausea was reported by 29.6% at month one, 25.9% at month two and 14.8% at month three. Changes in appetite were common — 44.4%, 55.6% and 40.7% across the three months — though rated as mild. A faster heartbeat was reported by 18.5% in the first two months and 11.1% in the third. One participant reported diarrhea; nobody reported vomiting.
In this study, “mild” means a score of 1 on a 0–3 scale: noticeable, but not distressing or limiting. Body weight was not systematically recorded, which the authors flag as a gap. When side-effect scores were added up rather than averaged, higher doses were moderately linked to a heavier overall burden.
How Much Weight Can This Study Carry?
The authors are direct about the limits, and they are substantial. Twenty-seven women is a very small group. Everyone knew they were receiving a cannabis extract, and there was no placebo arm, so expectation could explain part of the improvement. That matters especially in chronic pain, where placebo responses can be large — and even more so among patients who have exhausted other options and may pin their hopes on a new treatment. Participants were also not randomly drawn from all women with endometriosis, and all outcomes were self-reported through questionnaires.
Three months is short. Longer-term effects of regular THC on memory, hormonal regulation and the body’s own cannabinoid system are not well understood, particularly in women of reproductive age, and long-term THC exposure is known to make cannabinoid receptors less responsive in some people. The authors call for randomized, placebo-controlled trials with more participants and longer follow-up.
The study lands in a field where patient interest runs well ahead of clinical proof. A 2024 survey of German-speaking patients by the same research group found cannabis was rated the most effective self-management method, with a mean score of 7.6 out of 10, and around 90% of users said they had cut back on conventional painkillers. An international survey covered earlier by The Cannex found similar enthusiasm alongside legal and social barriers. But a 2022 systematic review of medical cannabis for gynecologic pain and a 2024 evidence review on endometriosis-associated pain both describe the clinical evidence as limited. The kind of randomized trial the Charité team calls for is what drug developers are now attempting, as with the prescription-grade CBD candidate for endometriosis being developed in the UK.
Where This Fits Legally
The study took place in Germany, where cannabis for medical purposes has been regulated under the Medical Cannabis Act (MedCanG) since 1 April 2024. It is prescribed by a doctor and dispensed only through pharmacies, which is how participants received their extract.
In the United States, the situation is different. Since April 2026, a federal order has placed FDA-approved drug products containing marijuana and marijuana covered by a state medical marijuana license in Schedule III, while all other marijuana remains in Schedule I pending a broader rescheduling decision. No cannabis-based medicine is approved by the FDA for endometriosis.
FAQ
Pain scores fell from an average of 6.81 out of 10 before treatment to 4.93 after three months, and women needed painkillers on fewer days. But there was no placebo group and participants knew what they were taking, so the study cannot show how much of this improvement came from the extract itself.
After a slow four-week build-up, the typical daily dose was about 10 mg of THC and 12 mg of CBD, split into 0.3 ml in the morning and 0.5 ml in the evening of an extract containing 12 mg THC and 14 mg CBD per millilitre. This was a supervised research protocol and not a dosing guide.
Nearly all participants reported at least one side effect. Tiredness, concentration and memory problems affected around 60% throughout, while nausea, anxiety and a faster heartbeat became less common over time. Most effects were rated mild, and one woman left the study because of side effects.
No cannabis-based medicine is FDA-approved for endometriosis. In states with medical marijuana programs, doctors can certify patients for state-licensed products, and since April 2026 such state-licensed medical marijuana is in federal Schedule III. Marijuana outside these programs remains in Schedule I, and rules on qualifying conditions and products differ from state to state.
Disclaimer
This article is for informational and educational purposes only and does not constitute medical, legal or pharmaceutical advice. It describes the findings of a single pilot study and does not recommend the use of cannabis or cannabis-based products for endometriosis or any other condition. Anyone considering treatment options should speak with a qualified healthcare professional. Laws governing cannabis and cannabis-based medicines vary by country and region and change over time; readers are responsible for checking the rules that apply where they live.
