A prominent PMS researcher, Barbara Parry, MD, of the
University of California, San Diego, recently established
that PMS is related to light and that phototherapy (light
therapy) can alleviate PMS symptoms.  Dr. Parry identified a
woman in southern California who only has PMS during the
winter months.  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.  (Phototherapy is best known for
treating SAD, Seasonal Affective Disorder.)
     Why did the phototherapy work?  When people are exposed
to bright light, they produce serotonin, a neuropeptide (a
chemical that carries messages between nerves) that helps us
feel calm, alert and happy during the day.  At night, when
it is dark, the brain produces less serotonin and more
melatonin, a neuropeptide that helps us sleep deeply.
    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 PMS sufferers for symptoms to appear.
    Using phototherapy, women with PMS can keep their
serotonin/melatonin levels high enough to prevent their PMS
symptoms from appearing. (Parry, Berga et al, 1991; Parry,
Rosenthal et al, 1987)  Using these lights, 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 which measures the amount of light our bodies
receive.  It also acts as a biological clock which 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 we spend much of our time
indoors, where we are deprived of ultraviolet light.
(Ultraviolet light is blocked by glass and most plastics.)
     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.
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