By Cristina Mestre
It’s not just cold outside, but the days are also
short. So it’s not unusual to have a
case of the winter blues. But if you’re
really feeling down and depressed, you could be suffering from
seasonal
affective disorder (SAD).
SAD is directly related to a decrease in sunlight during the
winter which can disrupt our bodies’ internal clock and cause us to feel
depressed. Fewer men are diagnosed with SAD than women, who make up 60 to 90
percent of SAD patients. In some cases,
SAD sufferers exhibit hibernation-like behaviors such as avoiding the outside,
as well as eating and sleeping more.
While antidepressants and increased exercise may help in
some cases, there is an alternative treatment that is proving extremely
effective: light therapy. Research has shown that light therapy can be used not
just for SAD, but also for treating non-seasonal mood disorders (major depressive
disorder or depression in pregnancy), the effects of jet lag or shift work, and
bulimia nervosa.
UPMC psychiatrist Dorothy Sit, M.D., notes that while early evidence
is promising, we still don’t know enough about the effectiveness of light
therapy for patients with bipolar disorder. She and her colleagues are
conducting a study examining the antidepressant effects of
light therapy to improve mood symptoms and circadian rhythms in depressed women
and men (ages 18-75) with bipolar disorder.
According to Dr. Sit, light therapy can generally be used to
alleviate a range of mood symptoms, sleep problems, and circadian (daily) rhythm
disturbances. Recent research found depressed patients
in brightly lit wards left the hospital approximately three days earlier than
those in darker wards, and a coronary ICU patient group with sunny rooms was
associated with a lowered mortality rate, she said.
How it might work: light or darkness provides signals to the
brain which promote sleep or wakefulness through effects on the hormone melatonin
that helps regulate sleep. Darkness
(twilight) prompts the brain to produce melatonin which makes us feel
sleepy. In contrast, morning light
prompts the brain to stop producing melatonin which helps us to wake up. We
need a minimum of 1,000 “lux,” a measurement that represents the level of
illumination, to synchronize our daily rhythms, but home or office lighting provides
only 50-300 lux. For SAD, the
recommended light box is a broad spectrum unit that filters out harmful UV rays
that cause skin cancer. The usual dose
is ~7000-10,000 lux for 45 minutes every morning, soon after you wake up.
Yet the
time
of day we receive this light is key. For example, if we have too much light at
night (especially blue-screened light from computers and mobile devices!) it
can throw off our bodies’ internal clock. But light also can affect attention/alertness,
memory, and our sensory processes.
As Dr. Sit explains, scientists still do not fully understand
the connection between light and mood.
Light can improve mood from indirect effects that promote stable
circadian rhythms. Or, light might improve
serotonin signaling in brain pathways which can alleviate depression and
restore a healthy mood state.
For patients who think they might have SAD, a proper
evaluation should come first. This is
very important because doctors do not recommend light therapy for some
conditions. Plus, other conditions symptoms
that are similar to depression (such as hypothyroidism) will need to be ruled
out. Moreover, SAD symptoms can be very similar to symptoms of bipolar
disorder, also known as manic depression.
During the course of light therapy for SAD, Sit recommends a
physician or informed provider such as a therapist provides close and careful
monitoring for adverse effects during the first two months of treatment.
