PMS is a psychoneuroendocrine disorder that causes a variety of physical and behavioral symptoms in the week before a woman's period begins, due to alterations in estrogen and progesterone levels. Common symptoms include mood swings, breast tenderness, bloating, headaches, and fatigue. While the exact cause is unknown, potential contributing factors include neurotransmitter levels, psychological factors, and hormones. Treatment focuses on lifestyle changes like diet, exercise and stress reduction, as well as hormonal birth control, antidepressants, vitamins, and herbal supplements to manage symptoms.