In some cases, hormones can offer relief. But now, new research describes an herbal remedy that appears to be as effective as medical treatment, with fewer side effects.
Whether this alternative approach deserves a green light, though, remains to be seen, other experts caution.
The herbal remedy - an extract of the fruit produced by the agnus castus plant, a delicate lilac-coloured herb also known as chaste tree - provides relief from irritability, bloating and breast tenderness, all common symptoms of PMS, say German scientists.
Many women experience a variety of such symptoms before their menstrual periods - everything from anxiety, depression and mood swings to food cravings. The symptoms, which can last from one to 14 days, affect from 30 percent to 50 percent of all women of childbearing age.
Little consistent evidence exists on the cause of PMS, however, and current medical approaches to the disorder concentrate largely on treating individual symptoms. Research has shown that exercise, a healthy diet and stress management can reduce symptoms. And because several studies have suggested that hormonal imbalance is to blame, the most widely tested medication is progesterone.
Synthetically manufactured progesterone is not always effective, however, and can have side effects that mimic or worsen PMS. Because of that, Dr Rüdiger Schellenberg, a senior consultant at the Institute for Health Care and Science in Huttenberg, Germany, has been searching for a natural alternative - and the doctor thinks he's found it in agnus castus extract.
"Agnus castus has been used in Germany and some other European countries for years, but there did not exist a large, placebo-controlled study to objectively study the clinical experience," Schellenberg says.
Along with several colleagues, he randomly assigned 86 women to take a 20-milligram tablet of agnus castus extract daily for three months, while another 84 women received a placebo. Neither group knew which pill they were taking. Each woman kept track of the severity of six PMS symptoms over that time.
At the end of the third cycle, Schellenberg found that women taking agnus castus extract had significantly reduced symptoms - except for bloating - compared with women who received the placebo. In fact, the women taking agnus castus extract reported a 50 percent improvement in their symptoms. Results of the study appear in this week's issue of the BMJ.
"The efficacy of agnus castus is comparable with that of hormonal pills [oral contraceptives], but with the [agnus castus] there are much fewer side effects," Schellenberg says. The extract creates no risk for blood clots in women who smoke, he says, while hormonal treatments do carry that risk.
"Now there is scientific evidence that the agnus castus efficacy is not a placebo effect," he says. "It is the action of this drug on several pathways which are still under research."
The reported side effects were mild, such as acne, spotting and hives. One woman in the placebo group withdrew from the trial after she became pregnant, he says, because the effects of the extract on a growing foetus are not fully understood.
That kind of caution is merited, says Judith Wurtman, a research scientist who studies PMS. While the effects of the herb are interesting and the study is promising, Wurtman says, much more information is needed about the active ingredient in this extract, how much is required and precisely how it works.
"What if you're taking other drugs, and whatever is in the [extract] preparation may interfere?" she says. In fact, some evidence exists that this extract should not be combined with the anti-psychotic drug haloperidol (Haldol), experts say, and the extract must not be taken along with oral contraceptives.
"You have to be very cautious," Wurtman says.