Premenstrual syndrome or PMS refers to a group ofphysical and psychological symptoms that occur in certain women prior to the onset of their menses and interfere with their normal routines. DSM-IV (1994) includes "Premenstrual Dysphoric Disorder" in the section of proposed categories that require further study, as there was not sufficient evidence to warrant its inclusion as an official disorder. The DSM-IV distinguishes between premenstrual syndrome and Premenstrual Dysphoric Disorder. It reserves the latter disorder for the more severe condition that interferes with work or social activities. DSM-IV considers premenstrual syndrome to be a much more common disorder than Premenstrual Dysphoric Disorder.