Working with a mouse model, researchers have shown relief of endometriosis symptoms using THC as a pain reliever.
Pain is complicated. Many things can cause pain, such as injury, disease, inflammation (swelling), pressure applied to body parts, and nerve damage. There are also many types of medications that attempt to help relieve pain – everything from aspirin to opiates has been prescribed by doctors to try and relieve the pain felt by their patients. However, there are some types of chronic pain that are hard to treat with medication. This includes the pain felt by women who suffer from endometriosis.
What is endometriosis?
Endometriosis is a medical condition where the cells from the endometrium (the inner lining of the uterus) grow outside of the uterus and even sometimes on other reproductive organs. The endometrium is the lining that is shed each month when a woman has her period. When endometrial cells grow outside of the uterus, they react as cells would in the endometrium, by thickening the layer of cells and causing bleeding during periods. But since the growth and bleeding happen outside the uterus, the cells and blood cannot exit the body the way normal period bleeding does, and this can cause pain.
Symptoms of endometriosis
Symptoms of endometriosis may include severe pain during menstruation (periods), excessive period bleeding, chronic pain in the pelvis and lower back, possible pain during sexual intercourse, infertility, issues with urination, constipation or diarrhea, and cognitive (thinking, memory) and emotional difficulties due to the levels of pain felt.
There is no easy solution for the pain felt by women who suffer from endometriosis. Traditional pain relief medication is not always successful in helping to manage endometriosis symptoms. Recently tetrahydrocannabinol (THC), the psychoactive ingredient in marijuana that causes users to feel a “high”, has been shown to be an alternative choice of treatment for some types of chronic pain.
Researchers in Spain wanted to know if the relief of endometriosis symptoms using THC is possible. They used a mouse model where they surgically implanted endometrial cells on the outside of the uteri of some mice while implanting fat cells in the uteri of control mice. That way, they could tell if any pain felt by the mice was due to the surgical procedure, or if it was specifically due to the endometrial cells on the uteri of the mice.
The scientists tested the endometriosis pain symptoms of the mice by testing their abdominal sensitivity to pain. Only the mice with the endometrial tissue showed abdominal pain sensitivity, which showed that the surgery had successfully imitated symptoms felt by women with endometriosis.
The researchers also tested for cognitive and emotional symptoms of these mice. They found that the mice had more cognitive difficulties and some memory loss, as well as an increase in anxiety levels. Once these symptoms were observed in the mice with the endometrial implants, the scientists then treated some of those mice with THC to see if any of their symptoms would decrease.
At first, they tested for pain sensitivity both on the abdominal regions of the mice, as well as with pain in a hind limb to see if there was any difference in how the mice reacted to the pain. After treatment with THC, the mice reacted strongly to the hind leg pain but were less sensitive in their abdomens, which indicated that the THC was helping to control the pain associated with endometriosis.
They also tested the brain functions of the mice by observing how they moved through mazes and how they reacted to new toys in their environment. What they saw was that the cognitive functions and memory of the mice with endometriosis returned much closer to a normal level. But what did not change was their anxiety level, which was still higher than the control mice.
Finally, the researchers took a look at the uteri of both the mice who had been treated with THC and those who had not. They were surprised to find that the mice that had been treated with THC had less endometrial growth on the outside of their uteri when compared to the mice that had not been treated with THC. This seems to indicate that the THC may have helped limit the growth of the endometrial cells, but only on the outside of the uterus. The endometrial linings inside the uteri of the mice were not affected by the THC.
There were some negative effects observed by the researchers when THC was given both to mice with and without endometriosis symptoms. There was a slight increase in the anxiety levels of both the endometriosis mice and the control mice that received THC doses.
Overall, there were many positive results showing relief of endometriosis symptoms using THC in the mouse model. This has encouraged researchers to apply for clinical trials in humans using THC to help reduce the pain and cognitive symptoms associated with endometriosis.
Cannabinoids improve symptoms in mice with endometriosis. eLife. Published January 14, 2020. https://elifesciences.org/for-the-press/84e17c36/cannabinoids-improve-symptoms-in-mice-with-endometriosis.
Escudero-Lara A, Argerich J, Cabañero D, Maldonado R. Disease-modifying effects of natural Δ9-tetrahydrocannabinol in endometriosis-associated pain. eLife. Published January 14, 2020. https://elifesciences.org/articles/50356.
Doheny K. Marijuana relieves chronic pain, research shows. WebMD. Published August 30, 2010. https://www.webmd.com/pain-management/news/20100830/marijuana-relieves-chronic-pain-research-show.
World Health Organization. Endometriosis. Published 2020. https://www.who.int/news-room/fact-sheets/detail/endometriosis.