Premenstrual Syndrome (PMS)
Premenstrual syndrome, or PMS, is a group of symptoms that start one to two weeks before menstruation. Most women have at least some symptoms of PMS, and the symptoms go away after their periods start. For some women, the symptoms are severe enough to interfere with their lives, which is a type of PMS called premenstrual dysphoric disorder (PMDD).
PMS is usually diagnosed if at least one of the symptoms listed above occurs during the five days before the start of menses for at least three cycles, two of which must be consecutive cycles. Additionally, these symptoms stop at least four days after the onset of menses and do not recur until the next cycle.
Over-the-counter pain relievers such as ibuprofen, naproxen, or acetaminophen may help ease mild PMS symptoms (e.g., cramps, headaches, breast tenderness). When symptoms of PMS are severe, selective serotonin reuptake inhibitors (SSRIs) such as paroxetine (Paxil), fluoxetine (Prozac), citalopram (Celexa), or sertraline (Zoloft) can be tried. Oral contraceptives have also shown some benefit for reducing PMS symptoms. Theoretically, these work by regulating fluctuations of estrogen and progesterone throughout a cycle.
Daily calcium supplements (calcium carbonate) have been shown to reduce symptoms of PMS. Vitamin D and vitamin B6 have also been assessed for PMS symptoms, but there is insufficient evidence to support their use. Many herbs have also been studied, with chasteberry having the greatest volume of evidence behind it.
Specific diets have not been studied for PMS. Some observational evidence has found that consuming foods high in calcium, vitamin D, thiamine, and riboflavin has been associated with a lower risk of PMS. Common dietary recommendations for PMS include small and frequent meals as well as reducing consumption of salt, caffeine, and refined sugars. These modifications are intended to reduce irritability, insomnia, fluid retention, bloating, and weight gain during PMS.
Exercise is often recommended for PMS because it can promote endorphin release which can improve mood and increase energy. Psychological modalities such as cognitive-behavioral therapy (CBT) and other modalities such as acupuncture with and without herbal medicine have been studied for relieving PMS symptoms. However, more research is needed to determine their benefits. 
No one knows what causes PMS. It is likely that changes to the levels of estrogen and progesterone and individual sensitivity to these changes trigger PMS symptoms. These hormones affect levels of neurotransmitters such as gamma-aminobutyric acid, dopamine, and serotonin which in turn can affect mood. Some evidence suggests that suppressing estrogen can improve PMS symptoms, and a deficiency of progesterone may worsen symptoms, but more research is needed.