About 80% of women experience some features of PMS. Fortunately, only a minority (estimated at 10%) of women have severe enough PMS symptoms to impact their work, relationships or lifestyle in a significant way.
PMS remains an enigma because of the wide-ranging symptoms and the difficulty in making a firm diagnosis. Several theories have been advanced to explain the cause of PMS. None of these theories has been proven and specific treatment for PMS still largely lacks a solid scientific basis.
Among the reigning theories are those relating to alterations in the levels of sex hormones, brain chemicals, and opioid peptides:
- Sex hormones: PMS has been thought (since the 1930's) to be due to decreased production of sex hormones by the ovaries after ovulation has taken place (in midcycle, or days 7-10 into the menstrual cycle). To date, this theory is still unproven.
- Neurotransmitters: Alterations in sex hormone levels at around the time of ovulation have also been thought to cause PMS. The changes in sex hormone levels affect certain brain chemicals which, in turn, bring about the mood changes of PMS. Serotonin and tryptophan, which function as neurotransmitters in the brain, have been shown to create PMS-like symptoms experimentally. These two chemicals have profound effects on mood and emotion.
- Opioid peptides: These are substances possessing some properties of opiate narcotics but are not derived from opium. They are also brain chemicals known to affect mood. The concentration of these compounds in the brain tissue can fluctuate in response to the hormones produced by the ovaries.
Because of genetic differences, some women can be more susceptible to these chemical changes in the brain and suffer more severe symptoms than others.