Endometriosis – this means for the affected women severe pain and abdominal cramps, painful periods and pain during sexual intercourse. The disease is very stressful and often leads to other complaints such as insomnia and depressive moods. Can cannabis help as a medicine?
Endometriosis – what is it?
According to estimates two to ten percent of all women in Germany are affected by the disease. However the number of unreported cases is high, because endometriosis is often symptom-free.
Women between the ages of 20 and 40 are most often affected. Since the condition is hormone-dependent, the symptoms improve with the menopause. Endometriosis is a chronic disease. Treatment options include surgery, medication or hormone preparations. However these treatment options are often not effective enough or are associated with undesirable side effects.
In endometriosis tissue similar to the lining of the uterus settles outside the uterine cavity. These islands of mucous membrane are subject to the hormonal cycle and can occur throughout the body.
Causes and risk factors
Until now the exact causes of endometriosis have not been clarified. However there are various explanations that are discussed among experts. Due to the familial accumulation, doctors assume that the disease also has genetic causes. Other risk factors for the development of endometriosis are an early onset of menstruation (between the ages of 11 and 13) and a late menopause, short menstrual cycles and a late first pregnancy.
Symptoms of endometriosis
Endometriosis patients suffer from both cycle-dependent and cycle-independent symptoms. The cells that have settled outside the uterus due to the disease react to the hormonal cycle just like the tissue of the uterus. This leads to cycle-dependent symptoms such as painful menstruation (dysmenorrhoea)
In addition, there may be irregularities in the cycle. These are for example:
- a prolonged cycle
- bleeding in between
- an unusually heavy menstrual period
The affected women often also suffer from complaints that are independent of the cycle. Permanent abdominal pain is caused by cysts or adhesions in the abdominal cavity. Endometriosis can also lead to sterility, problems with urination and bowel movements. Pain during sexual intercourse, which is usually caused by endometriosis lesions in the vagina, is particularly distressing.
The pain and other discomforts associated with the disease are so intense in some cases that sufferers are severely restricted in their daily lives. Insomnia and psychological problems can also occur as consequences of endometriosis. It is not uncommon for the worry of infertility to trigger anxiety or depression in young women.
Despite these serious symptoms, endometriosis can also be completely symptom-free. In many women who are operated on for other reasons, endometriosis presents itself by chance without ever having experienced symptoms before.
The role of the endocannabinoid system in endometriosis
Several years ago researchers looked at the influence of the endocannabinoid system (ECS) on the disease. A 2012 review suggests that certain cannabinoid receptor agonists can limit abnormal tissue growth and have a positive effect on pain control .
In 2017 another review paper from Israel evaluated the studies on endometriosis and the endocannabinoid system (ECS) available up to that time . The authors point out that the ECS has been found to be “an important factor in the development and maintenance of endometriosis” as well as in the pain mechanisms of the disease. These pain mechanisms associated with endometriosis are complex. They manifest as nociceptive, inflammatory as well as neuropathic pain.
The ECS is involved in many physiological processes: In addition to pain sensation, it is also involved in appetite, mood, memory and others. Some of the studies considered in the review described endometriosis as an endocannabinoid deficiency disorder. “Indeed, women with endometriosis have lower levels of CB1 receptors in endometrial tissue .” Researchers therefore suspect that decreased ECS function leads to the growth of endometrial tissue and a more severe pain experience. Therefore, the endocannabinoid system may be important in the development of pain associated with the disease.
Many studies advocate more effective treatment for patients with endometriosis. Therapy should address the pain, but also stop the proliferation of tissue outside the uterine cavity. Modulation of the ECS seems to the scientists to be “a good therapeutic strategy by potentially combining all these factors” .
Endometriosis and THC
A current study from the year 2020 comes from Spain. Scientists investigated the effect of THC on endometriosis using a mouse model . The female mice developed symptoms such as abdominal pain, anxiety and memory disorders due to the artificially induced endometriosis. The animals were treated with moderate doses of delta-9-tetrahydrocannabinol (THC). The drug reduced pain and cognitive impairment, but had no effect on their anxiety behaviour.
Another interesting result is that the scientists found that the growth of the endometrium was actually lower in the mice treated with cannabis. “Strikingly, THC also inhibits the development of endometrial cysts,” say the authors of the study .
THC could therefore be an effective treatment option. Clinical trials are already underway to see if these findings can also be applied to endometriosis patients.
Survey: Cannabis and CBD oil against pain
An Australian online survey from 2017 collected data on the so-called self-management, i.e. self-care and additional measures of endometriosis patients . The aim of self-management is to improve symptoms, increase well-being and reduce medication. Women between 18 and 45 years of age who lived in Australia and had a confirmed diagnosis of endometriosis could participate in the survey.
Three quarters of the interviewed women with endometriosis use self-management strategies. The most common were heat (70 %), rest (68 %) and meditation or breathing exercises (47 %). The survey showed that cannabis, heat, hemp/CBD oil and dietary changes were rated highest in terms of effectiveness in reducing pain (with a mean effectiveness of 7.6, 6.52, 6.33 and 6.39 respectively on a 10-point scale).
The endocannabinoid system seems to be an effective starting point for treating endometriosis. Further studies are necessary as there are no clinical studies available so far. The issue of fertility and pregnancy in connection with cannabis therapy also requires special attention.
 Sanchez AM, Vigano P, Mugione A, Panina-Bordignon P, Candiani M. The molecular connections between the cannabinoid system and endometriosis. Mol Hum Reprod. 2012 Dec;18(12):563-71. doi: 10.1093/molehr/gas037. Epub 2012 Aug 24. PMID: 22923487.
 Bouaziz J, Bar On A, Seidman DS, Soriano D. The clinical significance of endocannabinoids in endometriosis pain management. Cannabis and Cannabinoid Research 2:1, 2017, 72–80, DOI: 10.1089/can.2016.0035.
 Escudero-Lara A, Argerich J, Cabañero D, Maldonado R. Disease-modifying effects of natural Δ9-tetrahydrocannabinol in endometriosis-associated pain. Elife. 2020 Jan 14;9:e50356. doi: 10.7554/eLife.50356. PMID: 31931958; PMCID: PMC6977967.
 Armour M, Sinclair J, Chalmers KJ, Smith CA. Self-management strategies amongst Australian women with endometriosis: a national online survey. BMC Complement Altern Med. 2019 Jan 15;19(1):17. doi: 10.1186/s12906-019-2431-x. PMID: 30646891; PMCID: PMC6332532.