Endometriosis is a chronic condition that is estimated to affect around 176 million women globally, and approximately 1 in 10 women in the UK. It occurs when tissue similar to the lining of the womb begins to grow outside the uterus, most commonly in the pelvis but also in other parts of the body, including around the bowel and bladder. The condition can cause a range of symptoms, including abdominal pain, dysmenorrhea, chronic pelvic pain, and infertility. These symptoms can significantly affect the quality of life of individuals with endometriosis.
We are pleased to share the key findings from our latest study, “A Longitudinal Assessment of Endometriosis Patients Prescribed Cannabis-Based Medicinal Products: A Case Series From the UK Medical Cannabis Registry,” recently published in the Australian and New Zealand Journal of Obstetrics and Gynaecology. This research provides valuable, real-world evidence for patients exploring new options.
The UK Medical Cannabis Registry
This prospective case series utilised data from the UK Medical Cannabis Registry. The UK Medical Cannabis registry was launched by Curaleaf Clinic in 2019 to gather real-world data from patients who are prescribed medical cannabis to treat a range of conditions. It tracks patient-reported changes in symptoms and overall quality of life, as well as the occurrence of any adverse events (side effects).
The current analysis included data from 63 patients who were enrolled in the UKMCR for 18 months, completed baseline PROMs, and had a primary diagnosis of endometriosis.
PROMs were collected at baseline, 1, 3, 6, 12, and 18 months following initiation of medical cannabis treatment. They included:
- The Short-Form McGill Pain Questionnaire-2 – measures the characteristics and severity of pain.
- The Brief Pain Inventory Short Form (BPI) – measures pain severity and interference.
- Pain Visual Analog Scale (VAS) – measures pain on a scale or 0 (no pain) to 10 (worst possible pain).
- The Generalised Anxiety Disorder-7 (GAD-7) – used to screen and assess the severity of generalised anxiety disorder.
- The Single-Item Sleep Quality Scale (SQS) – a self-reported assessment of sleep quality.
- EQ-5D-5L – assesses health-related quality of life across five domains: mobility; self-care; usual activities; pain/discomfort; and anxiety/depression.
Examining Real-World Outcomes for Endometriosis Patients
The final analysis included 63 patients whose primary indication for prescribing medical cannabis was endometriosis. The average age of participants was 34 years. Over one-third of the patients (39%) were current cannabis users at baseline. All included patients were female (100%).
Patient-Reported Outcome Measures
The initiation of CBMPs was associated with changes across most health domains measured over the 18-month follow-up period.
- Pain: There were changes in all pain-specific measures, including the Pain Visual Analogue Scale (Pain VAS), Brief Pain Inventory (BPI), and Short-Form McGill Pain Questionnaire-2 (McGill) total score, from baseline to 18 months.
- Pain Severity & Interference: Changes were observed in both the BPI Pain Severity and Pain Interference subscales.
- Health-Related Quality of Life: The EQ-5D-5L index value (a measure of overall health-related quality of life) showed changes between baseline and all follow-up months (1, 3, 6, 12, and 18 months).
- Anxiety and Sleep: Outcomes for anxiety (GAD-7) and sleep quality (SQS) showed changes from baseline to 18 months.
Adverse Events and Tolerability
Adverse events were reported throughout 18 months of therapy by both patients and clinicians.
- Prevalence: A total of 62 adverse events were reported by 16 patients (25.40%).
- Severity: Most adverse events were categorised as mild (50%) or moderate (42.59%) in severity.
- The adverse events with the highest incidence were:
- Fatigue (25.40%)
- Lethargy (23.81%)
- Headache (20.63%)
- Dry mouth (19.05%)
- Insomnia (19.05%)
Key Considerations for Patients and Clinicians
This study offers important, large-scale, real-world data that complements the limited existing evidence on medical cannabis for endometriosis-associated chronic pain.
As an observational study, it cannot prove that medical cannabis was the cause of the changes observed. Causality, therefore, cannot be inferred. Improvements may be secondary to other factors like the well-documented placebo effect in cannabis studies or other therapies not recorded. The study highlights the urgent need for robust randomised controlled trials (RCTs) to confirm the efficacy and safety of medical cannabis for endometriosis.