Can Medical Cannabis Ease Endometriosis Pain? A Deep Dive into the Science

Endometriosis affects approximately 1 in 10 women of reproductive age, causing chronic pelvic pain, debilitating cramps, and a host of other symptoms that can significantly impair quality of life. In the UK, where diagnosis can take an average of 7.5 years, many women seek alternative therapies to manage their symptoms due to the limitations of conventional treatments like hormonal therapies and painkillers. One such alternative gaining attention is medical cannabis, specifically the compounds cannabidiol (CBD) and tetrahydrocannabinol (THC). This blog post explores the latest scientific research on how these cannabis compounds may help alleviate chronic pelvic pain and cramping associated with endometriosis, offering a balanced look at their potential benefits, limitations, and the current state of evidence.

Understanding endometriosis and its Challenges

Endometriosis is a chronic inflammatory condition where tissue similar to the uterine lining grows outside the uterus, often on the ovaries, fallopian tubes, or other pelvic structures. This tissue responds to hormonal changes, leading to painful periods, chronic pelvic pain, painful intercourse, and gastrointestinal issues. In the UK, treatments typically include non-steroidal anti-inflammatory drugs (NSAIDs), hormonal therapies, or surgery, but these often come with side effects or limited efficacy. For instance, NSAIDs like ibuprofen are frequently ineffective for endometriosis pain, and hormonal treatments can cause mood swings or impact fertility, prompting many women to explore alternatives like medical cannabis clinics.

The endocannabinoid system: A key player

The potential of cannabis in managing endometriosis pain lies in its interaction with the endocannabinoid system (ECS), a network of receptors (CB1 and CB2) and endogenous compounds that regulate pain, inflammation, and immune responses. Research suggests that women with endometriosis may have lower CB1 receptor levels in their endometrial tissue, which could contribute to heightened pain and disease progression. This “endocannabinoid deficiency” hypothesis has spurred interest in using external cannabinoids like CBD and THC to modulate the ECS and alleviate symptoms.

• CBD: A non-psychoactive compound, CBD is known for its anti-inflammatory and analgesic properties. It interacts primarily with CB2 receptors and other pathways, such as the Transient Receptor Potential Vanilloid 1 (TRPV1), to reduce inflammation and pain perception.
• THC: The psychoactive component of cannabis, THC binds strongly to CB1 receptors, which are abundant in the brain and reproductive tract. It can modulate pain pathways and relax uterine muscles, potentially easing cramps.

The “entourage effect,” where CBD, THC, and other cannabis compounds like terpenes work synergistically, is also thought to enhance therapeutic outcomes, making whole-plant or full-spectrum products potentially more effective than isolated compounds.

What does the research say?

Recent studies, particularly from 2020 to 2024, provide promising but preliminary insights into the use of cannabis for endometriosis pain. Below, we summarise key findings from the most up-to-date research, focusing on CBD and THC for chronic pelvic pain and cramping.

Retrospective cohort studies

A 2021 study published in PLOS One analysed data from 252 women with self-reported endometriosis who used the Strainprint app to track cannabis use between 2017 and 2020. The study found:

• Pelvic pain and cramps: Cannabis was effective in reducing pelvic pain (42.4% of participants used it for this purpose) and cramps (14.9%). Inhaled forms (e.g., vaporised flower, 67.4% of sessions) provided rapid relief, with a median dose of 9 mg/mL, while oral forms (e.g., edibles) were better for mood and gastrointestinal symptoms.
• THC vs. CBD ratios: Inhaled cannabis typically had a high THC:CBD ratio (median 90:1), suggesting THC’s role in acute pain relief. However, oral forms with higher CBD content showed greater efficacy for mood and gastrointestinal issues, with a reduction in efficacy of 4.75 (95% CI 5.62 to 3.88) for every 10-fold increase in THC compared to CBD.
• Limitations: The study relied on self-reported data, lacked a control group, and noted that illicit cannabis often has high THC levels (15–30% vs. 1–5% in the 1960s), which may not be optimal for all symptoms due to lack of standardisation.

Survey-based evidence

A 2024 study in Obstetrics & Gynecology reviewed 16 studies on cannabis for gynaecological pain, finding that 61–95.5% of participants reported pain relief. A cross-sectional survey of 113 women with chronic pelvic pain (including endometriosis) revealed:

• Usage patterns: 23% used cannabis, with 60% using a CBD-THC combination, 24% using CBD alone, and 12% using THC alone. Users reported improvements in pain, cramping, muscle spasms, anxiety, and sleep.
• Challenges: Cannabis users had higher rates of anxiety, depression, and catastrophising, suggesting that psychological factors may influence usage. There were no significant demographic differences between users and non-users.

A 2019 survey of 484 Australian women with surgically diagnosed endometriosis found that 13% used cannabis for pain management, rating it highly effective (mean score of 7.6/10), alongside heat, CBD oil, and dietary changes. This highlights cannabis’s role in self-care strategies, though the study noted potential bias due to self-selection.

Preclinical and mechanistic studies

Laboratory studies offer insights into how cannabis may target endometriosis at a cellular level. A 2020 study in eLife suggested that THC could have “disease-modifying effects” by reducing endometrial tissue growth in mice, potentially slowing disease progression. Other research indicates that cannabinoids may:

• Inhibit cell proliferation and migration, preventing lesion growth.
• Reduce inflammation by blocking prostaglandin synthesis, a key driver of endometriosis pain.
• Desensitise pain-transmitting nerves, easing chronic pain and cramps.

CBD’s anti-inflammatory effects were highlighted in a 2020 study in Antioxidative and Anti-Inflammatory Properties of Cannabidiol, which showed its ability to modulate inflammatory pathways, potentially reducing endometriosis-related inflammation.

Clinical trials

Clinical evidence remains scarce, but two ongoing trials in the UK and Canada are investigating CBD and THC for endometriosis pain. One phase II trial is testing a 1:1 THC:CBD ratio, while a phase III trial combines CBD (10 or 20 mg) with norethindrone acetate. Results are pending, but these trials could provide robust data on efficacy and safety.

Delivery methods and practical considerations

The effectiveness of cannabis for endometriosis depends on the delivery method, which influences onset, duration, and symptom targeting:

• Inhalation (vaping/smoking): Rapid onset (within minutes), ideal for acute pain and cramps. However, high THC content in inhaled forms may cause psychoactive effects.
• Oral (edibles, capsules): Slower onset (30–60 minutes) but longer-lasting effects, better for mood, sleep, and gastrointestinal symptoms. Higher CBD ratios are often preferred.
• Topicals (creams, suppositories): Targeted relief for pelvic pain with minimal systemic effects. Suppositories, like those with CBD and CBG, are gaining popularity for menstrual cramps and pelvic pain.

In the UK, medical cannabis has been legal since 2018 for conditions like chronic pain when conventional treatments fail. However, it can only be prescribed by specialists, and access remains limited due to cost, stigma, and lack of clinician education. Patients often turn to unregulated CBD products, which vary in quality and may lack the entourage effect of full-spectrum cannabis.

Benefits and risks

Potential benefits

• Pain and cramp relief: Studies consistently show that cannabis, particularly THC, reduces pelvic pain and cramping, with 61–95.5% of users reporting improvement.
• Reduced opioid use: Over 50% of cannabis users report reduced reliance on opioids, which is significant given the fourfold higher risk of opioid addiction in women with endometriosis.
• Holistic symptom management: Cannabis addresses comorbidities like anxiety, depression, sleep disturbances, and gastrointestinal issues, improving overall quality of life.

Risks and limitations

• Side effects: THC can cause dizziness, dry mouth, or psychoactive effects, while CBD may lead to nausea or fatigue in some users. Long-term use carries a risk of cannabis use disorder or mood disturbances.
• Lack of robust evidence: Most studies are retrospective or survey-based, with few randomised controlled trials. This limits national guidance in the UK, where cannabis is not routinely recommended for endometriosis.
• Regulatory challenges: Unregulated CBD products may contain inconsistent cannabinoid levels or contaminants. Patients using illicit cannabis face legal risks and variable potency.

What does this mean for UK patients?

For women with endometriosis in the UK, medical cannabis offers a promising but complex option. The science suggests that CBD and THC can reduce chronic pelvic pain and cramping by targeting inflammation, pain pathways, and the ECS, with inhaled forms best for acute relief and oral forms for sustained symptom management. However, the lack of large-scale clinical trials and regulatory hurdles mean that access to quality-assured medical cannabis remains challenging.

If you’re considering cannabis for endometriosis:

• Consult a specialist: Speak to a healthcare provider experienced in medical cannabis, as prescriptions require a specialist’s approval in the UK.
• Choose reputable products: Opt for regulated, full-spectrum products to ensure safety and efficacy. Avoid unregulated CBD oils, which may lack therapeutic potency.
• Start low, go slow: Begin with low doses, especially for THC, to minimise side effects. Work with your doctor to find the right CBD:THC ratio and delivery method.
• Monitor symptoms: Track your pain, mood, and side effects to assess efficacy, as individual responses vary.

The future of cannabis for endometriosis

The growing body of research, coupled with patient-reported benefits, underscores the need for more comprehensive studies. On-going clinical trials and increasing acceptance of medical cannabis in the UK could pave the way for better access and clearer guidelines. For now, while cannabis shows promise in easing endometriosis pain, it’s not a cure, and its use should be approached cautiously under medical supervision.

As research evolves, medical cannabis may become a cornerstone of holistic endometriosis management, offering hope to the millions of women navigating this debilitating condition. Until then, staying informed and working closely with healthcare professionals is key to safely exploring its potential.