University of Otago Study: Medicinal Cannabis Reduces Endometriosis Pelvic Pain and Improves Quality of Life in New Zealand

A groundbreaking observational study from the University of Otago has revealed promising results for women in New Zealand battling endometriosis. Researchers led by Dr. Claire Henry found that medicinal cannabis significantly reduced pelvic pain and enhanced quality of life over a 12-week period. This real-world evidence highlights the potential of cannabinoids as an adjunct therapy for one of the country's most debilitating chronic conditions.

Endometriosis affects approximately 1 in 10 women and people assigned female at birth in Aotearoa New Zealand, impacting up to 130,000 individuals during their reproductive years. Characterized by endometrial-like tissue growing outside the uterus—often in the pelvic region—it triggers intense pain, fatigue, heavy periods, and fertility challenges. Traditional treatments like hormonal therapies, surgery, and opioids frequently fall short, with high discontinuation rates due to side effects such as weight gain, mood changes, and dependency risks.

The Otago team's work, published in BMC Complementary Medicine and Therapies on January 22, 2026, underscores growing academic interest in non-opioid alternatives. As New Zealand universities ramp up research into women's health, this study positions the University of Otago at the forefront of innovative pain management solutions.

Endometriosis imposes a staggering toll on New Zealanders. Recent estimates peg the annual economic burden at up to $3.17 billion NZD, driven largely by productivity losses—accounting for 65% of costs for endometriosis and 75% for related chronic pelvic pain (CPP). Over a 34.5-year working lifespan, individual lifetime losses exceed $1.9 million INT$ for endometriosis patients, factoring in absenteeism, presenteeism, and early retirement.

Diagnosis delays average over six years, exacerbating suffering and costs. Patients cycle through ineffective interventions, from painkillers to laparoscopies, often without lasting relief. In New Zealand, cultural factors and healthcare access disparities amplify inequities, particularly for Māori (12.1% of surveyed patients) and Pasifika communities. This crisis demands urgent, evidence-based innovations—precisely what university-led research like Otago's aims to deliver.

Standard endometriosis management revolves around symptom suppression rather than cure. Hormonal contraceptives suppress ovulation but risk thromboembolism and bone density loss. Non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen provide short-term relief but irritate the gut long-term. Opioids, used by many, foster tolerance and addiction amid New Zealand's opioid crisis.

Surgical excision offers temporary respite—up to 68% of Otago study participants had prior procedures—but recurrence rates hit 20-40% within five years. Patient satisfaction remains low, with surveys showing widespread frustration. This gap fuels self-medication trends; prior New Zealand data indicated 81% of cannabis users with endometriosis reported pain reduction. Universities like Otago are bridging this divide through rigorous clinical inquiry.

The endocannabinoid system (ECS)—comprising cannabinoid receptors CB1 and CB2, endocannabinoids like anandamide and 2-arachidonoylglycerol (2-AG), and regulatory enzymes—modulates pain, inflammation, and reproduction. In endometriosis, ECS dysregulation promotes lesion growth, hyperalgesia (heightened pain sensitivity), and neuroangiogenesis (abnormal nerve and vessel formation).

Phytocannabinoids such as cannabidiol (CBD) and tetrahydrocannabinol (THC) interact with the ECS to curb inflammation, inhibit cell migration, induce apoptosis in ectopic tissue, and desensitize pain pathways. Preclinical models show cannabinoids reducing endometriotic lesion size by 40-50% and pain behaviors. Human surveys corroborate this, with 70-95% of users noting symptom relief—paving the way for studies like Otago's.

Dr. Claire Henry and colleagues at the University of Otago, Wellington, alongside collaborators from Western Sydney University and the Medical Research Institute of New Zealand, launched a prospective observational cohort study. Ethical approval came from the Otago Health Ethics Committee (H23/026).

Twenty-eight women (mean age 30, 46% NZ European, 18% Māori) with confirmed endometriosis received first-time prescriptions: 15 CBD oil only (starting 25mg/day), 13 CBD plus low-THC flower (average 0.32g/day). Participants self-titrated under clinician guidance while continuing standard care. Data collection spanned baseline, weekly pain visual analogue scales (VAS, 0-10), 12-week Endometriosis Health Profile-30 (EHP-30) questionnaire, and semi-structured interviews.

University of Otago's rigorous methodology exemplifies how New Zealand higher education drives translational research.

Pain relief was striking. Overall pelvic pain dropped 31% (5.46 ± 1.55 to 3.77 ± 2.25), worst pain 29% (7.62 ± 1.51 to 5.38 ± 2.69). Trends showed steady declines, more pronounced with CBD oil alone. EHP-30 scores plummeted 46% (68.77 ± 15.17 to 37.40 ± 16.66), surpassing minimal clinically important differences across pain, control/emotional health, support, and self-perception domains.

• Weekly VAS monitoring captured real-time improvements.
• CBD-only group: Greater QoL gains.
• Flower users: Effective for flares but variable.

These outcomes align with international registries, validating cannabis as a viable adjunct.

Interviews with 17 participants unveiled nuanced experiences. Many sought cannabis after exhausting options: “I gained 30 kgs in six months... ‘that’s normal’—it’s not!” (Participant 1). Benefits emerged gradually: better sleep first, then pain control, reduced opioid use (e.g., tramadol from 60 to 10-15 doses/month).

Four deemed it “life-changing,” 10 “helpful for management.” Challenges included nighttime dosing for impairment (“can’t drive for six hours”) and parental stigma. Cost loomed large—“unattainable”—alongside GP hesitancy: “Doctors say, ‘I don’t know anything about it.’”

Safety shone through: only mild, self-resolving events (nausea n=1, headaches n=3, fatigue/drowsiness n=2). No serious adverse reactions, underscoring low-risk profile versus opioids. This real-world safety data reassures clinicians wary of cannabinoids.

Otago's findings echo global reviews: cannabis outperforms traditional meds for many, with fewer side effects.

Despite legalization in 2020, barriers persist. High costs ($200-500/month unsubsidized), GP reluctance (citing evidence gaps), stigma, and impairment concerns deter access. Women face gender-specific hurdles, sometimes reverting to illicit sources. Reforms like streamlined approvals help, but policy tweaks—subsidies, education—are needed.

New Zealand Ministry of Health lists approved products, yet uptake lags.

The study spotlights University of Otago's translational prowess in gynaecological research. Dr. Henry's team, funded by EndoWarriors Aotearoa and industry partners (non-influential), calls for randomized controlled trials (RCTs) to confirm causality, optimize dosing, and track long-term effects. Ongoing NZ efforts, like the EndoCann trial, build momentum.

Implications extend to policy: integrate cannabis into guidelines, fund access for underserved groups. For higher education, it signals booming demand for researchers in pharmacology, women's health—check higher ed research jobs in New Zealand.

Photo by Elsa Olofsson on Unsplash

As New Zealand universities like Otago, Auckland, and Canterbury advance endometriosis research—from self-compassion interventions to cost modeling—the medicinal cannabis findings catalyze collaboration. Aspiring academics can explore NZ university jobs or career advice to join this vital field. Patients, rate your professors at Rate My Professor and seek specialist care.

Future outlooks: RCTs could redefine standards, slashing the $3B+ burden. Until then, Otago's work empowers hope.