New Clues for Cause of PMS Symptoms

Dec. 20, 2007 -- New research may help explain why some women experience terrible symptoms with their monthly periods while others do not.

Findings from a small, but intriguing, new study from Japan show significant differences in heart rate variability among women, suggestive of a critical role for the nervous system in premenstrual syndrome (PMS) and its more severe form, premenstrual dysphoric disorder (PMDD).

The study focused on the part of the nervous system that controls involuntary processes like heart beat, respiration, and digestion, known as the autonomic nervous system (ANS).

The findings suggest that this area may be permanently depressed in women with the most serious menstrual-cycle-related symptoms, researcher Tamaki Matsumoto, PhD, tells WebMD.

"We have found that an imbalance in ANS may be a cause of PMS, but not the only cause," she says. "However, the findings must be confirmed in larger studies."

Causes of PMS

Most women who menstruate experience some degree of distress and discomfort immediately before or during their monthly periods, and 3% to 8% have symptoms severe enough to disrupt their lives and/or relationships, studies suggest.

There are many theories about the causes of PMS, but no definite physiological trigger has been identified.

In the newly published study, Matsumoto and colleagues examined whether the activity of the autonomic nervous system was altered during the menstrual cycle.

Researchers measured heart rate and hormone level variability for the 62 women in their 20s to 40s with regular menstrual cycles. The women also filled out questionnaires designed to evaluate physical, emotional, and behavioral symptoms associated with menstrual cycles.

Heart rate variability throughout the month was measured as an indicator of ANS activity.

The researchers found little differences in ANS activity during the month in women with few or no symptoms of PMS, but significant decreased activity in women with PMDD.

PMS and Heart Rate Variability

Women with PMS showed differences in heart rate variability around the start of their monthly periods.

Women with PMDD also showed significantly decreased heart rate variability throughout the month, suggesting that a permanently depressed nervous system is linked to severe cycle-related symptoms.

"Does this imply that women with lower autonomic function regardless of the menstrual cycle are vulnerable to more severe premenstrual disorders?" Matsumoto and colleagues write. "Clinical research on the menstrual cycle has been conducted from various perspectives. ... However, at the moment, the underlying biomechanisms of PMS remain enigmatic."

If the findings are confirmed, heart rate analysis may prove to be of value in the medical management of women with PMS and PMDD, Matsumoto says.

The study appears in the latest online version of the journal BioPsychoSocial Medicine.