It is not known why some women, as they approach their menstrual flow, experience these mood changes.

For most women, these symptoms are either very mild or absent, while others have moderate or severe symptoms. For them, the symptoms may begin around the time of ovulation and persist until the menstrual flow has begun. For others, the mood changes are limited to a day or two preceding the menstrual flow.

About 80% of women with moderate to severe premenstrual mood changes will obtain significant relief from BCPs. The blocking of ovulation seems to be the key element as very low dose pills or progestin-only pills sometimes do not have the same effect.

If BCPs are not available or the patient is not a good BCP candidate, any medication which blocks ovulation will likely have good results. Unfortunately, some of these medications (Lupron, DEPO-PROVERA, Danazol) have depression and irritability as potential side-effects, so the patient must be closely watched.

Anti-depressant medications (Prozac, etc.) are also about 80% effective in improving the mood changes associated with the premenstrual syndrome. These are not, however, the same 80% who benefit from BCPs, so for BCP failures, a therapeutic trial of antidepressant medication may be considered. Whether such a trial is appropriate in an operational setting should be individually determined.