May 4 (HealthDay News) -- Relapse is common among women with severe premenstrual syndrome (PMS) who stop taking the antidepressant sertraline to treat their symptoms, a new study concludes.

It included 174 women with PMS or the most severe form of PMS -- premenstrual dysphoric disorder (PMDD). The women were randomly assigned to take sertraline for four months and then switch to placebo for 14 months or to take sertraline for 12 months and a placebo for six months.

Of the 174 patients, 125 (72 percent) showed improvement following treatment with sertraline, most within the first four months. Relapse (a return to the level of symptoms experienced before treatment) occurred in 41 percent of women in the 12-month treatment group (median time to relapse, eight months) and in 60 percent of women in the four-month treatment group (median time to relapse, four months).

"Patients with severe symptoms at baseline were more likely to experience relapse compared with patients in the lower symptom severity group and were more likely to experience relapse with short-term treatment," wrote Ellen W. Freeman and colleagues at the University of Pennsylvania School of Medicine in Philadelphia. "Duration of treatment did not affect relapse in patients in the lower symptom severity group."

The study found that the 41 women (24 percent) who experienced remission (reduction of PMS symptoms to normal post-menstrual level) after four months of treatment with sertraline were least likely to experience relapse after they stopped taking the drug.

"How long medication should be continued after achieving a satisfactory response and the risk of relapse after discontinuing treatment are important concerns for women and clinicians, given the possible adverse effects and cost of drugs vs. the benefit of medication that improves symptoms, functioning and quality of life," the study authors wrote.

"These findings suggest that the severity of symptoms at baseline and symptom remission with treatment should be considered in determining the duration of treatment," they concluded.

The study appears in the May issue of the Archives of General Psychiatry.

SOURCE: JAMA/Archives journals, news release, May 4, 2009