Lack Of Light And Seasonal Depression - What's The Link? From The Harvard Health Letter

People troubled by
depression usually experience their dark moods in an on-again, off-again
fashion. In that respect, seasonal affective disorder (SAD) differs only in
that the oscillations follow a seasonal schedule, with the depression
usually starting in the fall and lasting through the spring. Lack of light
is often blamed for SAD, but just how darker days cause depression in SAD
sufferers is still in question, reports the January 2008 issue of the
Harvard Health Letter.


Experts debate whether it has been proved that lack of sunlight in
winter triggers SAD, but there's certainly circumstantial evidence to
support the connection. How might lack of light cause depression? The
Harvard Health Letter discusses three theories:


1. The root cause may be insensitivity to light. Most of us go
through winter on a relatively even keel because exposure to
indoor lighting helps offset the lack of natural light, but
indoor light may be too weak for SAD sufferers.


2. There are neural pathways from the eyes' retinas to parts of
the brain that help put many of our physiological processes
on a 24-hour cycle. Lack of light may put people with SAD out
of phase with their biological clocks: awake and active when
their internal timers want them snug in bed.


3. A lack of light, or insensitivity to it, may disrupt
brain processes influenced by serotonin and dopamine, brain
chemicals that play a role in mood.



Light therapy, which involves sitting in front of a bright light for a
short time each day, helps some people who suffer from SAD. But
antidepressant medications may work just as well, says the Harvard Health
Letter.


Harvard Health Letter

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