Menstrual periods and their attendant torment affect billions of people, yet we know relatively little about them. Why do we have them? Are they really necessary? However, there may be some progress in finding out what's behind it all. A large study found that women with higher levels of inflammation also reported more severe premenstrual pain, bloating, and mood swings. The study results were published in the Journal of Women’s Health.

Premenstrual symptoms (or "PMSx," as they are called in the study) may be the subject of a lot of insensitive jokes, but they’re really no laughing matter. In addition to the unpleasant menstrual bleeding itself, four out of five women report experiencing monthly depression, irritability, weight gain, headaches, and any combination of abdominal, back, and breast pain. These symptoms are so common, intense, and intrusive that 50 percent of women surveyed reported seeking medical help to deal with them.

Inflammation is neither inherently good nor bad. Acute inflammation is a response to an invader in the body, like a foreign bacteria or virus, and it helps us heal. Chronic inflammation, on the other hand, can lead to pain and illness. A possible relationship between inflammation and PMSx is not a new idea; some doctors already prescribe anti-inflammatory drugs to patients with PMSx. But to date, most of the studies conducted on the subject have been small and focused on younger white women. To fully test the hypothesis, researchers would need to collect data from a large, diverse group of women, and that’s exactly what they did.

Three researchers from the University of California-Davis pulled information on 2939 women from five different ethnic backgrounds (Caucasian, African-American, Latina, Japanese, and Chinese)from the Study of Women’s Health Across the Nation (SWAN). Because the SWAN study focuses on women in midlife, the participants were all between the ages of 42 and 53. To remove some hormonal variability, they couldn’t be pregnant, in menopause or perimenopause, or on any form of hormones, including oral birth control.

Each participant’s information included two key factors: the extent of her PMSx and the levels of high-sensitivity C-reactive protein (hs-CRP) in her blood. This protein is a good indicator, or biomarker, of cellular inflammation; higher levels typically mean more inflammation.

Sure enough, the data found that inflammation and PMSx go hand in hand. On average, women with higher levels of hs-CRP reported more premenstrual mood symptoms; abdominal, back, and/or breast pain; weight gain; and appetite changes and/or bloating. Interestingly, the researchers found no significant relationship between hs-CRP levels and headaches, nor did they see a link between high hs-CRP and experiencing more than three symptoms.

Like many studies, this one had its limitations. The authors note that their analysis did not consider external factors like whether women were treating their PMSx, if they were taking anti-inflammatory drugs, if they had been diagnosed with depression or other inflammation-linked conditions, or even if they had infections at the time of the study. Not all the ethnic groups were equally represented, and some included relatively small sample sizes. The study only looked at some, not all, premenstrual symptoms, and it focused only on symptoms, not premenstrual syndrome (PMS), which the researchers say is a separate entity. Additionally, the participants were all women in midlife, and it's possible that the results would be different for younger women. The authors did note that the inflammation-PMSx link seemed strongest in younger participants (that is, those closer to 42 than 53) and those in perimenopause. The bottom line: We need more studies on this subject.

All the same, it’s fair to conclude that inflammation is not helping. That doesn’t mean that we should all start taking anti-inflammatory drugs, the researchers say; rather, we should think hard about behavioral changes, like quitting smoking, that can help reduce chronic inflammation.