The exact causes of PMS are not fully understood. While PMS is linked to the luteal phase, measurements of sex hormone levels are within normal levels. In twin studies, the concordance of PMS is twice as high in monozygotic twins as in dizygotic twins, suggesting the possibility of some genetic component. Current thinking suspects that central-nervous-system neurotransmitter interactions with sex hormones are affected. It is thought to be linked to activity of serotonin (a neurotransmitter) in the brain. Recent studies in rats indicate that levels of glutamate, an excitory neurotransmitter, spikes prior to menstration in the cortex and hippocampus. High glutamate levels have been tied to mood disorders in several studies.
Preliminary studies suggest that up to 40% of women with symptoms of PMS have a significant decline in their circulating serum levels of beta-endorphin. Beta endorphin is a naturally occurring opioid neurotransmitter which has an affinity for the same receptor that is accessed by heroin and other opiates. Some researchers have noted similarities in symptom presentation between PMS symptoms and opiate withdrawal symptoms.
In one study of 71 women with PMS, elevated levels of serum pseudocholinesterase were found. This enzyme is considered a possible marker for trait-anxiety.
A variety of evolutionary rationales for the syndrome have been offered, including that it is an epiphenomenon due to the selective advantage accruing to other phases of the hormonal cycle, that it leads to "intensification of male ardour during the next onset of fertility", and that it prompts females to reject infertile males (who cause PMS due to not impregnating the female). "... an infertile male/potentially fertile female partnership would tend to break down, thus allowing a new pair-bond to be formed. The greater the degree of premenstrual hostility of the female, the sooner a fertile mating could ensue." Any theory would have to account for the persistence of PMS over substantial evolutionary time, as it appears to afflict baboons as well.
Many researchers have also put forth the theory that PMS is caused primarily by cultural factors.
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