Women suffering from premenstrual syndrome should react cautiously to a new report suggesting that a common antibiotic may help ease symptoms in some, says a National Institute of Mental Health researcher.

Dr. David Rubinow, a psychiatrist and clinical director at the institute, said many treatments have been proposed for premenstrual syndrome (PMS) but none have been proven to work."I think the whole area of premenstrual syndrome has been characterized by a new story and a new treatment every year for the last 50 years," he said.

He made the comment following an announcement Tuesday that the antibiotic doxycycline could ease symptoms in women who had an unrecognized underlying infection. The report by Dr. Atilla Toth, a gynecologist at the New York Hospital-Cornell Medical Center in New York, was published in The Journal of International Medical Research.

At a press conference, Toth said that 15 women who were given the antibiotic and asked to rate their symptoms showed a "highly significant improvement."