Drinking liquids that contain caffeine -- regardless of the amount consumed -- appears to be related to premenstrual syndrome, according to researchers at Oregon State University.

In the Oregon study, published in the September's American Journal of Public Health, researchers Annette Mackay Rossignol and Heinke Bonnlander enlisted 841 female students in what they were told was a "study of women's health." The subjects were asked to complete a detailed questionnaire listing symptoms of PMS and their severity and to keep a diary of liquids consumed, including water, as well as coffee, tea and diet sodas, many of which contain caffeine.

The study, conducted between October 1988 and January 1989, found that 616 women -- 73 percent of those who participated -- reported at least one premenstrual symptom and 603 women reported consuming at least one cup of a caffeine-containing beverage daily, mostly in the form of soda.

Researchers discovered that the more severe the symptoms of PMS -- typically anxiety, depression, mood swings and bloating -- the more caffeine had been consumed.

The researchers suggest that the elimination of caffeine could ease the severity of PMS symptoms within a few months. "Because there are few, if any, known beneficial effects associated with caffeine-containing beverage consumption," they wrote, women with PMS "may want to consider elminating {them} from their diets."