Researchers have a lead on an explanation for why period pain and premenstrual symptoms (PMS) can suck so much for some women.
In a large 2016 study, scientists found a link between an inflammation biomarker and PMS severity, which suggests that acute inflammation could be triggering all the cramps and bloating.
Researchers have known for ages that anti-inflammatory drugs can greatly help period pain - and most doctors already recommend them for patients looking to soothe their raging wombs.
But this was the first large-scale study to identify a biological link between inflammation and PMS, and it could one day help scientists find more effective treatments than the over-the-counter painkillers we're currently using.
After surveying 2,939 women in the US, a team from the University of California, Davis, showed that there was a positive correlation between PMS severity and the presence of something called high-sensitivity C-reactive protein (hs-CRP).
Hs-CRP is a biomarker for inflammation in the body, so the researchers suggest that the more of this protein someone has, the more inflammation they're likely to experience, and the worse PMS a woman is likely to suffer - excluding headaches.
"Premenstrual mood symptoms, abdominal cramps/back pain, appetite cravings/weight gain/bloating, and breast pain - but not headache - appear to be significantly and positively related to elevated hs-CRP levels, a biomarker of inflammation, although with modestly strong associations, even after adjustment for multiple confounding variables," the researchers reported in the Journal of Women's Health.
This is a big deal, because around 80 percent of women report experiencing PMS. And yet there has been very little research done into either its causes, or potential treatment options. Right now, the best options we have is ibuprofen, over the counter painkillers, or - if it's really serious - one lonely prescription anti-inflammatory.
Some new devices also claim to 'switch off' period pain electronically, but it definitely doesn't stop the symptoms of PMS altogether.
That basically means millions of women have had very little choice other than to put up with a combination of everything from cramps and nausea, to vomiting and depression, every month, for the majority of their lives.
Earlier in 2016, John Guillebaud, a professor of reproductive health at University College London, told Quartz that period pain can be as "bad as having a heart attack", adding that the field has been overlooked because "men don't get it".
But if we can find out more about the biological factors that contribute to PMS, we might have a chance of developing better treatments, or at least identifying those at greater risk. And figuring out the link with inflammation gives scientists some clues as to what to look into next.
"The results also suggest that the factors associated with each premenstrual symptom are complex, suggesting potentially different mechanisms for the aetiologies of some symptoms ... Inflammation may play a mechanistic role in most PMS, although further longitudinal study of these relationships is needed," the team wrote.
"However, recommending to women to avoid behaviours that are associated with inflammation may be helpful for prevention, and anti-inflammatory agents may be useful for treatment of these symptoms."
A version of this article was originally published in June 2016.