A recent study of more than 60,000 women appears to show a link between child abuse and endometriosis, a disorder in which tissue that normally lines the inside of the uterus instead grows outside, sometimes causing pelvic pain and in some cases, infertility.

Researchers found that among the 60,595 premenopausal women with endometriosis who responded to the survey, 31 percent reported they’d experienced some form of physical abuse as children.

According to the researchers, another 12 percent reported being sexually violated, while 21 percent disclosed both types of abuse.

The study in the journal Human Reproduction, funded by the National Institute of Child Health and Human Development among other organizations, is the largest of its kind, said Holly Harris, ScD, an ovarian cancer and endometriosis researcher at the Seattle-based Fred Hutchinson Cancer Research Center.

“The numbers themselves are pretty staggering even though they are in line with reports of abuse in other studies,” Harris said. “I think the main thing we’re hoping for is that this brings awareness that abuse and endometriosis are prevalent. That number was far too high.”

The responses add to the growing body of evidence of how childhood trauma and stress can impact long-term health outcomes, Harris said.

“We saw stronger associations among women whose endometriosis was most likely diagnosed as a result of pain symptoms,” Harris said. “We know that abuse is associated with chronic pelvic pain. Potentially there’s a stress response to the trauma that activates these systems and causes you to be more sensitive to pain.”

The differences between women who had trauma and those who didn’t were large.

Researchers found that among women who had been through severe or chronic abuse, there was a 79 percent increased risk of being diagnosed with endometriosis (confirmed in surgery), compared to women who hadn’t been abused.

The risk was calculated by comparing different abuse categories of which severe-chronic abuse was one abuse category, to a reference group which was women who didn’t report any physical or sexual abuse, Harris said.

“This is a relative risk, not absolute risk” she added. “So it does not mean that women who were abused have a 79 percent chance of developing endometriosis.”

Harris also cautioned that the study doesn’t definitively mean all women with endometriosis experienced abuse.

She also acknowledged that more research is needed to understand the biological connection between trauma and physiological symptoms.

How prevalent is endometriosis?

Endometriosis affects about 1 in 10 women of reproductive age in the United States according to the American College of Obstetricians and Gynecologists. It can be one cause of infertility.

While it’s a common condition, the exact causes of why it occurs remain unclear.

Genetics and environmental factors have both been listed as possibilities.

The lead theory suggests the cause may be due to retrograde menstruation — a process that involves menstrual blood flowing back through the fallopian tubes and into the pelvic cavity instead of leaving through the vagina.

Though endometriosis can usually be managed with birth control or minimally-invasive laparoscopic surgery to remove the lesions, relief is often delayed until a woman is in her 30s or even 40s because symptoms can be mistaken for pelvic inflammatory disease or irritable bowel syndrome.

While the latest study on endometriosis and childhood trauma raises new questions, more research is needed to continue to scientifically understand the condition, said Dr. Mitchell S. Kramer, chairman of the department of obstetrics and gynecology at Northwell Health’s Huntington Hospital in Huntington, New York.

“Does the stress inadvertently impact the immune system? I think that opens a whole new avenue in research,” Mitchell said.

“This (study) is a jumping off point,” he added. “I really think (researchers) need to look at genetics further. We know there are hereditary factors.”

Kramer noted there has been a raised level of awareness among physicians to consider endometriosis when patients report pain and infertility.

An overlooked condition

In recent years, a surge of activism among women with endometriosis has helped to increase awareness.

Celebrities such as Lena Dunham, Padma Lakshmi, Cyndi Lauper, and Dolly Parton have stepped forward to talk about their experiences.

This year, U.S. Senator Orrin Hatch of Utah called the disease “nothing short of a public health emergency.” In an op-ed for CNN, Hatch disclosed his granddaughter had it and encouraged greater awareness and research.

Still, activists with endometriosis want increased scientific research as to why the condition occurs and a more immediate response when it comes to treatment.

Too many women live with this for too long until there’s a diagnosis, said Wendy Bingham, a Vancouver, Washington-based doctor of physical therapy who wasn’t diagnosed until she was well into her 40s.

She said she’s concerned the recent study will continue a myth that the condition is “in our head.”

“Moving forward with attempts to understand this disease better, we must remain cognizant of the historical dismissal that has — and continues to occur — surrounding this disease,” she said.

Harris, the lead researcher of the study, said the intent behind the work was to move away from the notion that women’s health problems are “all in their heads.”

“I think the biggest thing we want to get across is that abuse is far too common for everyone and as a society we need to find how to address that,” Harris said.

“Many patients are concerned that this type of research will bring more of a stigma to endometriosis, but as researchers that’s not what we’re hoping to do. We want to raise awareness.”