| Light
therapy, in one form or another, has been used as a treatment
for a number of conditions since ancient times. Nearly 2,000
years ago, Greco-Roman physicians were treating depression
and lethargy with sunlight directed toward the eyes.
During his Arctic expeditions in the 1890s,
Frederick Cook, M.D., noticing the profound influences of
light on the voyagers and Alaskan natives, described a syndrome
characterized by depressed mood, fatigue, and loss of energy
and sexual desire. In 1946, H. Marx reported the use of bright
artificial light to treat four men who had become depressed
during an Arctic winter.
Since the first study of light therapy in
winter seasonal affective disorder (SAD) (Rosenthal et al.,
1984), a syndrome in which depression developed during fall
or winter and remitted the following spring or summer for
at least two successive years, numerous studies have concluded
that bright light therapy is an effective treatment for SAD.
Light therapy is commonly administered by
means of a light box--a metal structure containing fluorescent
tubes behind a plastic diffusing screen. The dose of light
exposure can be measured with the intensity and duration of
the exposure. Efficacy is dose dependent to some extent, with
both duration and intensity being important. Before starting
light therapy, an ophthalmologic consultation is recommended
for patients with a pre-existing retinal or eye disease or
a systemic illness that affects the retina.
Side effects of light therapy include headaches,
eyestrain, fatigue and insomnia. Most of these side effects
respond to dose reduction. Hypomania and mania are uncommon,
but serious, side effects. Light treatment is best prescribed
by psychiatrists who have experience in its use and can appropriately
evaluate the indication for light therapy and monitor the
response to treatment.
Some individuals buy light boxes using the
Internet or from stores and carry out the treatment without
prior consultation and adequate supervision. Patients should
be discouraged from treating themselves without medical supervision.
However, patients can be encouraged to participate in establishing
an optimal light protocol.
For patients with SAD, light therapy should
be regarded as the first-line treatment, but other treatments
including antidepressants, stress management, exercise and
psychotherapy may also be useful.
The biological mechanisms of SAD and light
therapy are not clear. Various studies suggested the involvement
of serotonergic, dopaminergic and noradrenergic pathways;
the hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid
axes; and changes in circadian rhythm and melatonin secretion
in the neurobiology of seasonal changes in mood and behavior
and effects of light therapy.
Use of light treatment for nonseasonal depressive
disorders is growing. There may be a role for light therapy
in treating nonseasonal depression, especially in cases where
antidepressants are not tolerated or where the patient preference
is for nonpharmacological treatment. A recent study found
that there were seasonal influences on morning cortisol levels
in patients with major depression.
It is interesting to speculate that the hypothalamic-pituitary-adrenal
system is involved in the biological mechanisms of light therapy
in nonseasonal depression.
Exposure to bright light is important for
psychological well-being of healthy people. In the modern
industrial world, many people spend a lot of time indoors.
They are light-deprived and have a sedentary lifestyle. Combined
exposure to bright light and physical exercise can be especially
effective for improving mood- and health-related quality of
life. Various outdoor activities may provide opportunities
to improve psychological and physical health. |
