Strange as it may seem, PMDD does not appear to be caused simply by an imbalance of female ovarian hormones. Research measuring estrogen and progesterone levels across the menstrual cycle found no difference between women with PMDD and those without the disorder. On the other hand, hormones must play some role because PMDD symptoms disappear if the ovaries are removed or not functioning (e.g., menopause). Current theories suggest that normal ovarian function may trigger changes in brain chemistry in women predisposed to PMDD. One brain chemical that may be especially important is serotonin, a neurotransmitter. The serotonin system has a close relationship to the female hormones, and imbalances of the serotonin system may play an important role in causing PMDD. Another tie-in is that medications most effective for treating PMDD are those with specific effects on serotonin (for more information, visit the "how is it treated?" section).
People sometimes wonder if PMDD is inherited. Genetics may play a role. Studies have shown that identical twins are more likely to share the disorder (93%) than non-identical twins (fraternal) (44%), and daughters of mothers with PMDD are more likely to have it themselves. However, no specific genes have been identified to account for PMDD. Perhaps it is best to simply say that there may be a genetic predisposition to developing the disorder.
Psychological, social and cultural factors also may be involved in causing PMDD or at least in the expression of PMDD symptoms. These factors alone, however, are inadequate to explain the disorder, which almost certainly has a biological basis.
