Most women (90%) experience some degree of premenstrual symptoms (PMS) during the menstrual cycle's luteal phase and some 20%-30% report moderate to severe symptoms. At the more severe end of the symptom scale is premenstrual dysphoric disorder (PMDD). Some 3%-8% of women in their reproductive years have symptoms that are severe enough to be called PMDD. Still, there is yet another menstrual category, premenstrual magnification (PMM), and this term describes women who have symptoms throughout their cycles with an exacerbation of symptoms, be they medical, gynecological, or psychiatric, just before menstruation.
These three terms comprise a large variety of symptoms that can be mild to very severe and yet it is difficult for a clinician to confirm a diagnosis. Therefore, it's not at all surprising that until today, no one can explain PMS with any degree of certainty.
For one thing, PMS is diagnosed through the process of exclusion. This suggests that there may be several conditions with connections to PMS, though such associations are not well understood.
Theories abound attributing PMS to fluctuations of the sex hormones and the neurotransmitters. This idea arises from the fact that the symptoms disappear when menstruation begins. During menstruation, a woman doesn't ovulate and there is no formation of the corpus luteum. Experts therefore posit that estrogen and progesterone, both produced by the corpus luteum, bear responsibility for premenstrual symptoms.
Besides this theory there is the idea that serotonin and gamma amino butyric acid (GABA) both neurotransmitters, have a bearing on premenstrual symptoms. Throw in a host of other hormones and their own particular methods of activity and you have an endless list of mechanisms that have been blamed for PMS. So many ideas have been put forth and yet there is no certain answer. Perhaps the difficulty is that there is no way to test such a plethora of theories in a timely manner.
But one theory stands out because it is very different than the rest. According to this theory, PMS is caused by a large number of chronic infectious ailments that are worsened by the cycle of changes in immunosuppression brought about by rising and falling levels of estrogen and progesterone. Research conducted on this topic have found only a modest correlation between PMS, chronic infection, and immunosuppressive changes caused by hormone fluctuations. There is as yet, no hard and dried evidence exists for this idea.
Proponents of the theory explain that immune function changes during the course of the menstrual cycle as the levels of various hormones fluctuate. According to this train of thought, chronic infections worsen during the luteal phase and this leads to symptoms of PMS. Some of the infections that are mentioned as becoming more active in the days before menstruation include yeast infections (Candida albicans), cytomegalovirus, an increase in the number of herpes lesions, and a worsening of peptic ulcers arising from Helicobacter pylori. Examples of other ailments that worsen just before menstruation include: multiple sclerosis, Crohn's disease, rheumatoid arthritis, lupus, chronic fatigue syndrome, and asthma.