Norman Swan: For something that affects one in three women and costs sufferers about $30,000 a year in lost work and healthcare costs, we don't know enough about endometriosis. That's when the tissue similar to the lining of the uterus grows elsewhere in the body and can cause pain, especially pain in the pelvis, and even infertility. And so awareness of endometriosis is much better than it used to be but it was often dismissed as a women's issue. But a new genetic study is showing endometriosis has a genetic link to depression and gut issues and there might be a cause-and-effect link. Hi Tegan, you've been looking at this.

Tegan Taylor: Hi, yes, it's a crazy link to be showing, isn't it. It's the sort of thing where you go maybe if you had debilitating pain every month and your doctors couldn't give you an answer, it wouldn't be surprising if you are depressed. But actually looks like the genetic cause and effect link actually works in the other direction.

Norman Swan: So tell me about the study.

Tegan Taylor: So this is a really big study that looked at a couple of big genetic databases, and basically they were looking for a shared genetic risk factor for depression and endometriosis because they knew that observational studies have shown that in women with depression, they are twice as likely as the general population to have endometriosis, and similarly in women with endometriosis they are twice as likely as the general population to have depression. So there seemed to be a link there.

And so they were looking for a shared genetic risk factor, and they found several actually. And then when they did more analysis, they showed this cause-and-effect relationship between depression on endometriosis, and they both seemed to have a causal relationship with something that is involving the gastric mucosa, so gastrointestinal reflux disease or gastritis peptic ulcers. And so there does seem to be some kind of linear relationship between the genes that are maybe malfunctioning to cause these gastric conditions and things like depression and endometriosis.

Norman Swan: These studies are called Genome Wide Association Studies, so they are not gene sequencing, they are looking at 700,000 separate points in the genome, and these points called SNPs are near where genes might be, and they have been criticised as exercises in just gathering data which might not be important or they might just be accidental associations.

Tegan Taylor: Yes, it fits into a broader field of research where we've got these observational studies on one side where it looks like people are more likely to have one of these things if they've got the other thing, but you can't show the cause-and-effect. And so I spoke to one of the researchers from the study, Dale Nyholt from the Queensland University of Technology, and he said that when you look at the genetics, you're able to draw a clean link between endo and these other conditions.

Dale Nyholt: As a geneticist, we always look at genetics because it's less influenced by some of these other environmental factors that could make something look like it's comorbid, but if we find shared genetic risk factors, well that's in your germline, so that's what you've inherited. And by doing these type of analyses that we've done, we really confirm and validate that there's something that's biologically shared across individuals that suffer these traits.

Norman Swan: That's Dale Nyholt from the Queensland University of Technology. So what does this mean for women living with endometriosis, Tegan?

Tegan Taylor: Well, when I started reporting on this study I thought I'd put the call out to my friends and family, see if there's anyone who I knew who had this experience. I was staggered by the number of people who replied, and the stories are just heartbreaking. And that idea of what Dale just said about validating, he was talking about validating in a scientific sense, but I think for women personally it is very validating to hear that this is a genetic thing.

Delayed diagnosis is really common with endometriosis. People don't feel seen or understood or, like you said at the beginning, they are dismissed as having women's troubles. But in addition to that, this lack of continuity of care and this frustration of being sent back and forth between doctors. So, one woman was being treated for endometriosis and was told that she had irritable bowel syndrome, but when she saw a gut doctor they were, like, no, you've got endometriosis, and she is just being flicked back and forth between specialists. So this appreciation that these cases might be interlinked is really valuable.

And so one of the people I spoke to was Sophie Volker, and she's got a history of depression as well as endometriosis and gut problems, but like many women it took her a really long time to get a diagnosis, and her doctors didn't immediately draw the link between the three conditions.

Sophie Volker: I had had really painful periods, had had gut problems forever, just thought that was a pretty normal part of my life. And so I think the confusion of not having any kind of answers, not having a diagnosis and having pain all the time probably did contribute a little bit to my being depressed.

Norman Swan: That's Sophie Volker. I mean, it's fine to say there's a genetic link, and the researchers think it is cause and effect, but if it is cause and effect, what's the biological mechanism?

Tegan Taylor: They think it has something to do with inflammation, so these genetic pathways, it's not like the only job that they have is to give someone endo or to give someone depression, they're gene sequences that have to do with cell death and repair, and they do all sorts of different things, but they think that inflammation is playing a role.

And so one of theI mean, yes, you sort of do this genetic analysis and then it's up to some other group of researchers to figure out what to do with, but there have been some other studies already into whether diet interventions, for example a low FODMAP diet can be helpful in people with endometriosis, and they've had promising results. So this helps put that into context and it would be good to see more research in that space.

And it also has implications for the sorts of medications that people are prescribed. So if you've got a gut problem, then taking a nonsteroidal anti-inflammatory for your endometriosis pain might not be appropriate because you've got gut problems. But also because we do know what genetic pathways might be involved now, then those pathways and genes could be potential targets for drugs, especially in those people who have both endometriosis and depression.

Norman Swan: And I suppose the other thing is that there is evidence from some interesting antidepressants, tricyclics, that they can have odd effects that have got nothing to do with actually their antidepressant effects, and it could be that you start to use antidepressants not for necessarily their effect on depression but they could have an effect on the endometriosis.

Tegan Taylor: Perhaps, exactly, and it also highlights the importance for screening. So if you've got someone coming in with, say, depression and gut problems and they are a woman, screening them for endometriosis as well because there is a higher than average likelihood that that woman also has endometriosis.

Norman Swan: Have we given GPs a lot of work after today's Health Report! You've got to work out the fish oil tablets, and you got to work out the depression and they've got problems in endometriosis, all serious issues.

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Endometriosis and depression: is there a genetic link? - ABC News