Normal premenstrual symptoms, called "molimina," can include moodiness, increased appetite, bloating and breast tenderness. While PMS has similar symptoms, what sets it apart is the severity of those symptoms.

Although there is no specific treatment for PMS (placebos work in many cases, [Michelle Warren] notes), and the scientific explanation for PMS is still vague, Warren believes an expert should still be consulted for help.

"PMS falls on the edge of science," she says, "and we're in an area where people are doing a lot of research. If you think that you have PMS, it's best to consult a PMS specialist, someone who's usually a reproductive endocrinologist. Most major hospitals will be able to make recommendations."