PMS (Premenstrual Syndrome) Linked to Lack of Light

Prominent PMS researcher, Barbara Parry, MD, of the University of California, San Diego, recently established that premenstrual syndrome is related to light and that phototherapy can alleviate PMS symptoms. Dr. Parry identified a woman in southern California who has PMS only during the winter. Parry used specially designed lights to regulate the woman’s serotonin levels during the day and sleep cycles at night. The woman’s PMS symptoms were substantially reduced.

Researchers at UCLA (Rapkin et al., 1987) have shown that serotonin levels drop just before ovulation in all women. Rapkin shows that this drop correlates with the onset of PMS symptoms, and that serotonin levels rebound with the onset of menstruation when PMS symptoms decrease. This and other recent research suggests that PMS occurs in women with low base levels of serotonin; when serotonin levels drop further at ovulation, these levels fall low enough in women with premenstrual syndrome for symptoms to appear.

Using phototherapy women with PMS can keep their serotonin/melatonin levels high enough to prevent PMS symptoms from appearing. (Parry, Berga et al, 1991; Parry, Rosenthal et al, 1987) Using light, PMS women frequently report less depression, less moodiness, better sleep, better concentration, etc.

Researchers used to believe that PMS, which is obviously linked to the menstrual cycle, must be caused by a hormonal imbalance. We are now learning that PMS seems to be caused by cyclical irregularities in brain neurotransmitters, particularly serotonin, rather than by hormones.  A study reported in the New England Journal of Medicine (Schmidt et al., 1991) suggests that although PMS is usually synchronized with a woman’s menstrual cycle, it does not seem to be caused by the hormonal fluctuations that trigger that cycle.

The lack of quality light and resulting low serotonin affects many people, both female and male. This is especially true in January, February and March even though the days are getting longer. Our brains function like solar-powered batteries which run down when there is not enough light. When the sunlight increases, it takes a while to recharge our batteries. Scientists have discovered that our brains have a built-in “light meter” in the brain’s pineal body that measures the amount of light our bodies receive. It also acts as a biological clock that times the length of exposure. The type of light (visible color balance and presence or absence of the beneficial ultraviolet A and ultraviolet B) is also registered by the body. Surprisingly, many people remain deprived of the benefits of full spectrum light in the summer because so much time is spent indoors where glass blocks UV wavelengths.

Light deprivation is particularly common in the northern tier of the country, where light is less intense year-round and where it is frequently colder, keeping people indoors, and in areas such as the Pacific Northwest that have frequent cloud cover.

Hahn, L. PMS: Solving the Puzzle – Sixteen Causes of Premenstrual Syndrome and What to Do About It, Chicago Spectrum Press 1995.

Parry, B L et al. “Altered Waveform of Plasma Nocturnal Melatonin Secretion in Premenstrual Depression,” Archives of General Psychiatry 47 (1991): pp. 1139-46.

Parry, B L, Rosenthal N, Tamarkin, L & Wehr, T. “Treatment of a Patient with Seasonal Premenstrual Syndrome,” American Journal of Psychiatry 144, no. 6 (June 1987): pp. 762-66.


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