Light Regulation of the Menstrual Cycle

The night light effect on long cycles in oligomenorrheic women seems to be a genuine and rather powerful biological effect and not a result of suggestion.

Abstract

Abstract The 1967 report of Edmund Dewan that a bedside 100 watt bulb could stabilize irregular menstrual cycles was initially greeted with skepticism. Recent studies of light treatments of humans have indicated that both bright and dim light have real biological effects. To examine the validity of Dewan's report, our group has treated two samples of women with irregular menstruation with randomly-assigned 100 watt bedside night lights or dim red light placebos. In both groups, the 100 watt treatments significantly decreased the duration of menstrual cycles and reduced their variability. Effective were treatments both from days 10–14 and from days 13–17 of the menstrual cycle (counting the first bleeding as day 1). The night light effect on long cycles in oligomenorrheic women seems to be a genuine and rather powerful biological effect and not a result of suggestion. Use of light to regulate menstrual cyclicity may have clinical value both for rhythm contraceptive methods and for treatments of infertility. Further study of night light effects on the menstrual cycle may expand our understanding of reproductive endocrinology. Extensive clinical testing is needed to determine the optimal intensities, timing, and durations of night light treatments for producing endocrine benefits.