Endometriosis can reprogram the brain, causing anxiety and depression 鈥� according to research in mice. The findings suggest the common disorder may put the one in ten women who have it at risk of mental health problems.
Endometriosis is caused by uterus lining (endometrium) cells moving elsewhere in the body where they can compress nerves and bleed in time with a woman鈥檚聽menstrual cycle. It affects 176 million women worldwide and can cause聽severe pain as well as infertility.
But despite being a common disorder among women of reproductive age, we know very little about it. What causes bits of a women鈥檚 uterine lining to turn up elsewhere in the body remains mysterious, but one theory is that menstrual blood somehow moves up through the pelvis, carrying tiny bits of tissue into other organs as it travels.
Advertisement
This can cause excruciating pain, which probably partly explains why women who have endometriosis are also at risk of depression and anxiety. But , of Yale University, and his team have been investigating if some women develop mood disorders directly as a result of uterus cells聽migrating elsewhere.
Signs of endometriosis have been found in organs all over the body, including the lungs, throat and brain. To see what effect this might have, Taylor鈥檚 team had to mimic this in mice. These animals don鈥檛 menstruate like people, so to get the process started, the team removed some of the mice鈥檚 endometrial cells and implanted them into their abdominal cavities.
A separate group of mice had a sham surgery, in which they were operated on but did not have any endometrium moved.
Mental health tests
When the team assessed the mice twelve weeks later, they found characteristic endometriosis cysts in their bodies.
They then ran the mice through a series of tests to examine their mental health. A standard test for mouse depression, for example, is to hold a mouse up by the tail. A healthy mouse will squirm while a depressed mouse will flop motionless. Another test involves putting a mouse in an enclosure with a wide open space 鈥� healthy mice will explore the scene, while anxious animals will retreat to the darkest corners.
In a different test, each of the mice were placed on a hot plate that steadily increased in temperature. The test is used to measure an animal鈥檚 pain threshold by scoring how much heat it can withstand before it leaps off. 鈥淭his is not about endometriosis pain, but how sensitive they are to painful stimuli,鈥� says Taylor.
Across all of the tests, the mice with endometriosis were different to the mice that had undergone sham surgery. 鈥淭hey had a lower threshold for the hot plate, they had more anxiety and they were more depressed,鈥� says Taylor. 鈥淭his was caused by the endometriosis.鈥�
Altered perception of pain
When Taylor鈥檚 team looked inside the brains of the mice, they found more differences. In the mice with endometriosis, the activity of genes linked to anxiety, pain and movement had changed in brain regions known to be involved in pain and mood.
鈥淲e are showing that endometriosis reprograms the brain,鈥� says Taylor who presented his findings at the annual meeting in San Antonio, Texas, last month. It isn鈥檛 known yet how endometriosis might be having these effects.
, of the University of Edinburgh, UK, isn鈥檛 convinced though. She says the depression and anxiety experienced by women with endometriosis probably has more to do with the pain and infertility they experience.
But she agrees that endometriosis is a disease that affects the whole body, not just a woman鈥檚 reproductive organs. that endometriosis causes changes in the brains and spinal cords of mice that lower pain threshold, making them more sensitive to pain.
Greaves hopes the research will encourage researchers and clinicians to focus on pain. 鈥淩esearch in endometriosis has been significantly held up because the people who work in endometriosis are gynaecologists or basic scientists who work in reproductive health,鈥� she says. 鈥淣ow, from our work and Taylor鈥檚 work, we know there are changes in the central nervous system.鈥�
Taylor hopes that, by better understanding the disease, doctors might better be able to diagnose and treat it. At present, it can take ten years of symptoms before a woman is diagnosed.
鈥淚f you treat it early, maybe you can prevent some of these manifestations [like pain and anxiety], which could be life-altering for women,鈥� he says.
Read more: A home test kit may let you diagnose endometriosis years earlier
