Premenstrual stress syndrome (PMS, also called Premenstrual stress, Premenstrual tension, PMT) is stress which is a physical symptom prior to the onset of menstruation. The male equivalent is called irritable male syndrome (IMS).

PMS is exceedingly common, occurring in 75% of women of reproductive age during their lifetime. A more severe form of PMS is premenstrual dysphoric disorder (PMDD). This occurs in about 5% of women. Both are characterized by symptoms of mood swings, depression, anxiety and irritability that occur prior to menses, usually in the two week period between ovulation and menses. It is often accompanied by physical symptoms of abdominal bloating and cramping.

Diagnosis of PMDD requires a persistence of symptoms for several menstrual cycles, and differentiation from major depression and anxiety disorders.

Treatment usually begins with lifestyle modification. Reducing caffeine, sugar and sodium intake may help. Supplements of vitamin B6 and calcium carbonate have been shown to help reduce symptoms. Vitamin B6 should be taken in doses of 50 to 100 micrograms per day. Calcium carbonate should be taken in doses of 1200 milligrams a day. Exercise will help reduce depression and anxiety symptoms. Keeping a symptom diary will help cue sufferers to exacerbating and relieving strategies.

Prescription treatments include the selective serotonin reuptake inhibitors, like Prozac, Zoloft, Paxil and Celexa.

PMS in jurisprudence

As a term of jurisprudence, this may be used as a so-called "innovative defense" (and is perhaps better defined as either an excuse or justification); via which, a defendant may argue that she should not be held criminally liable for actionss which broke the law.

In the United Kingdom (1980), Christine English was found "not guilty" of murder; as, although she killed her boyfriend, she was suffering from PMS.

In the US, the Fayetteville Observer-Times reported (June 7, 1991) that Geraldine Richter (Fairfax, Virginia) had been acquitted of drunk driving charges, because of PMS, despite a 0.13% blood-alcohol level. A gynecologist testified on Richter's behalf.