The exact cause of premenstrual syndrome (PMS) has not been understood though it has been largely attributed to the fluctuating levels of the hormones estrogen and progesterone. The levels of these hormones alter in preparation of the menstruation and this is a normal phenomenon. However, the alteration brings along with itself a host of symptoms that constitute the premenstrual syndrome (PMS).
Another causative factor that is proposed is the alteration of the levels of serotonin in the brain. Serotonin is a chemical (neurotransmitter) that plays a crucial role in mood states. Lower levels of serotonin lead to feelings of sadness, depression, fatigue food cravings, sleep changes, etc.
Stress has also been seen to worsen certain cases of premenstrual syndrome (PMS) but it may not be likely to be the sole reason for the PMS.
Drinking alcohol and caffeinated beverages, (that can cause mood changes), taking excess of salty foods (that cause fluid retention), etc. may also worsen the symptoms of premenstrual syndrome (PMS).
Deficiency of certain vitamins and minerals may also be a contributing factor.