Those of us who are free from the chronic pain caused by endometriosis can only imagine what a life of constant discomfort is like. Depression can feel like an inevitable consequence, risking assumptions that distract us from looking for other causes.
Now, research led by geneticists at Queensland University of Technology in Australia has uncovered a number of risk factors that increase the chances of developing endometriosis and depression as well as a variety of gastrointestinal conditions.
While it doesn’t rule out an environmental impact, the discovery makes it clear that gut health, endometriosis and chronic mood disorders often coincide thanks to genes common to all three.
Endometriosis is the presence of endometrial tissue – the thick layers of cells lining the uterus – where it does not grow.
Like the endometrium, this tissue is also affected by cyclical fluctuations in hormones, which can cause internal bleeding, scarring and inflammation. In its most aggressive form, it penetrates deeply into surrounding organs and tissues, such as the bladder, colon, and ligaments that hold the muscles around the organs in place.
Although endometriosis is believed to affect about one in ten women, totaling about 200 million worldwide, the consequences of this rogue lining range from completely asymptomatic to living with chronic, debilitating pelvic pain.
Typically, the condition manifests itself through a range of symptoms and conditions, including excessive bleeding, pain during intercourse and menstruation, nausea and indigestion.
Additionally, it is not uncommon for people diagnosed with endometriosis to also experience bouts of anxiety and depression. Research supports this and found that these are the most common conditions found in connection with endometriosis.
It is not a big leap to assume that this relationship is causal. Studies conducted on mice also imply that the pain from endometriosis can directly affect the brain, promoting pain sensitization and mood disorders.
Plus, having higher levels of pelvic pain makes depression even more likely, making it seem like it’s the pain that’s causing depression, and not endometriosis itself.
Without necessarily contradicting the role of pain in influencing our mood, researchers are increasingly aware of the sheer complexity of depression, discovering that it is more than a psychological state, but rather a whole physiological system that becomes influenced by a rich variety of genes.
Twin studies have also strongly suggested a genetic basis for endometriosis. To see if any of the genes involved can predispose individuals to depression as well, researchers used data from a genome-wide association study (GWAS) conducted by the International Endogenous Consortium.
The sample of more than 208,000 individuals included approximately 17,000 cases of endometriosis, with just under 192,000 serving as controls, all from a diversity of countries around the world.
This was compared to a similar GWAS database previously used to find genes related to depression, with a number of alternative databases used to see if their findings could be reproduced.
After conducting an assessment of overlapping mutations that have both in common, the researchers identified 20 independent locations on the genome that could be considered significant for both conditions, eight of which are completely new.
A total of 22 genes were involved, many of which play a role in pathways that regulate cell adhesion, signaling that regulates cell movement and proliferation, and gastric health.
In fact, extra digging revealed further causal links between endometriosis and depression and at least one abnormal bowel condition, such as stomach ulcers or gastroesophageal reflux disease.
Knowing that links can be genetic is one thing. Mapping the intricate mess of pathways from genes to health and back is a whole different story.
We are still a long way from a cure and even finding suitable treatments is a constant challenge. Given that we’ve known about the condition for nearly a century, it’s shocking that endometriosis is still so often overlooked.
It’s not worth it to know more about the underlying genetics and how they can play out in other health conditions.
This research is published in Human Genetics.