Seasonal Affective Disorder and Light Therapy
2.Incidence of SAD and relation to latitude
affects mood and sleep
6.Side effects of light therapy
9.Other uses of bright light therapy
Throughout the centuries, poets have described a sense of
sadness, loss and lethargy which can accompany the shortening days of fall and winter.
Many cultures and religions have winter festivals associated with candles or fire. Many of
us notice tiredness, a bit of weight gain, difficulty getting out of bed and bouts of
“the blues” as fall turns to winter.
However some people experience an exaggerated form of these
symptoms. Their depression and lack of energy become debilitating. Work and relationships
suffer. This condition, known as Seasonal Affective Disorder (SAD) may affect over 10
million Americans while the milder, “Winter Blues” may affect a larger number of
The typical symptoms of SAD include depression, lack of energy,
increased need for sleep, a craving for sweets and weight gain. Symptoms begin in the
fall, peak in the winter and usually resolve in the spring. Some individuals experience
great bursts of energy and creativity in the spring or early summer. Susceptible
individuals who work in buildings without windows may experience SAD-type symptoms at any
time of year. Some people with SAD have mild or occasionally severe periods of mania
during the spring or summer. If the symptoms are mild, no treatment may be necessary. If
they are problematic, then a mood stabilizer such as Lithium might be considered. There is
a smaller group of individuals who suffer from summer depression.
SAD is recognized in the DSM-IV (The American Psychiatric
Association’s diagnostic manual) as a subtype of major depressive episode. The classic
major depression involves decreased appetite, decreased sleep, and often, poor appetite
and weight loss. It has long been recognized that some depressed individuals had a
“atypical depression” with increased sleep and appetite along with decreased
energy. Some, but not all of these atypical individuals also had a seasonal pattern. Some
people with winter depression also have mild or occasionally severe manic mood swings in
the spring and summer. If these episodes are severe, the individual might be diagnosed
with Bipolar Disorder. (formerly called manic depressive illness)
About 70-80% of those with SAD are women. The most common age of
onset is in one’s thirties, but cases of childhood SAD have been reported and successfully
treated. For every individual with full blown SAD, there are many more with milder
“Winter Blues.” The incidence of SAD increases with increasing latitude up to a
point, but does not continue increasing all the way to the poles. There seems to be
interplay between an individual’s innate vulnerability and her degree of light exposure.
For instance, one person might feel fine all year in Maryland but develop SAD when she
moves to Toronto. Another individual may be symptomatic in Baltimore, but have few
symptoms in Miami. Some individuals who work long hours inside office buildings with few
windows may experience symptoms all year round. Some very sensitive individuals may note
changes in mood during long stretches of cloudy weather.
affects mood and sleep
In 1984, a psychiatrist at NIMH, Norman Rosenthal, published a
paper on the use of bright light therapy in patients with this disorder. Since then, a
large number of well-designed studies have confirmed and refined these findings.
Researchers are still investigating mode by which bright light can lift depression or
reset a sleep cycle. One theory is that an area of the brain, near the visual pathway, the
suprachiasmatic nucleus responds to light by sending out a signal to suppress the
secretion of a hormone called melatonin. Brain studies suggest that there is impairment
serotonin function in neurons leading to the suprachiasmatic nucleus.
Initial theories suggested a pathway from the retina to the suprachiasmatic nucleus. However some recent research indicated that bright light applied
to the back of an individual’s knee could shift human circadian rhythms. (Daily sleep-wake
cycle) This suggests that the bloodstream, not just the neurons of the visual pathways,
might mediate the biological clock.
Before embarking on a course of light treatment, it is best to
have a complete psychiatric evaluation. Sometimes a medical illness or another psychiatric
condition can masquerade as depression. Discuss various treatment alternatives with your
doctor. Light therapy does take time, and regular use. Like exercise, not everyone who
would benefit from it will actually do it on a regular basis. Your doctor will discuss the
various types of light boxes or visors available. The time spent in front of the light is
related to the intensity of the light source and the distance one sits from the light. The
light devices cost about $250 to $500 and often are not covered by insurance. I will often
lend out a box for a month so that the individual can see whether it helps before
purchasing a box.
Some individuals who use a 10,000-lux box may only need 30
minutes of daily light treatment. However, the amount of light needed varies widely from
individual to individual. The light treatment is most often done in the morning, but
studies have suggested that either morning or evening light can help SAD. Some people may
get insomnia when they use the light in the evening. Initially, researchers felt that one
needed full spectrum light. Now, studies suggest that regular fluorescent lights will work
as well. UV (ultraviolet) light can damage eyes and skin, so it must be filtered out. It
is best to buy a commercially built light box to be sure of the exact amount of light and
to be sure that there are no isolated “hot spots” which could damage eyes. Many
people still prefer full spectrum (minus UV) light because it is closest to natural
The individual measures the distance from her face to the light
source. This measurement is important, and should be repeated daily for several days and
occasionally after that. The light needs to strike one’s eyes, but one does not need to
look directly into the light source. It is fine to occasionally glance directly into the
light. Many people read a book or eat breakfast while using the lights. Sitting still for
30 minutes to several hours is not an option for some people. For these people, the light
visor is an option. Others are able to take one of the compact light boxes to work and use
it for several hours. It is best to use the light source in an uninterrupted time block,
but it can be helpful even with some interruptions.
Long term treatment compliance is often more difficult than one
might initially anticipate. This is an important reason to have a professional monitoring.
Having to account for your regular use (or the lack thereof) is a powerful motivator. It
is also helpful to have an outside objective individual to help monitor your response to
Since one of the symptoms of SAD can be difficulty awakening in
the morning, some find it helpful to have the light turn on just before they are supposed
to wake up. Some individuals like to use a Dawn Simulator. This is a bright light that is
programmed to gradually increase its intensity such that it reaches its full intensity a
set period before the individual is scheduled to awaken. Although it is less gentle, some
people will put their light box beside their bed and hook it up to a timer set to turn on
shortly before awakening.
Some people like to use full spectrum light bulbs for everyday
household use. There is no evidence that these low intensity bulbs affect mood or sleep
phase. Your plant light will not cure your SAD. Your 10,000-lux light however, may be nice
for some of your plants.
Outdoor light, even when the sky is overcast, provides as much or
more light than a light box. There has been a study showing improvement in SAD symptoms
when individuals took a one-hour daily walk outside. Outside light is often brighter than
the light boxes. Spending an hour outside each day can often produce beneficial results in
some individuals. However, one cannot get early morning outside light in the winter. Not
everyone’s job will allow for an hour-long outside walk. Only highly motivated people will
continue their daily walk when it the rains or snows.
SSRI (Selective Serotonin Reuptake Inhibitors–Paxil, Zoloft
etc.) have been shown to be effective in SAD and in some cases of PMS. Some people prefer
to take a pill because it is less time consuming than sitting in front of a light box.
Some individuals need a combination of light therapy, medication, and psychotherapy. For
those with winter depression and spring-summer mania, a mood stabilizer such as Lithium
may be useful.
Daily exercise has been shown to be helpful, particularly when
done outdoors. For those who tend to crave sweets during the winter, eating a balanced
diet may help one’s mood. Conversely, as the mood improves, craving for sweets may abate.
Psychotherapy can help the depressed individual look at her
depressive assumptions and negative expectations. It can also help one identify
relationship difficulties so that interpersonal mistakes might not be repeated. Research
has shown that cognitive psychotherapy does help relieve depression faster and more
completely than no therapy.
Some individuals continue to have a certain amount of energy
fluctuation with the seasons. If one is aware of this, one can plan for it and work the
expected fluctuations into one’s life plans.
Side Effects of Light therapy
Potential side effects of light therapy are rare and most often
include jitteriness, a feeling of eyestrain and headache. Light therapy, like
antidepressant medications, occasionally will cause someone to switch into a manic state.
There has been debate on whether there might be long term retinal effects, but none have
been documented when lights with proper screening of UV wavelengths are used. Individuals
taking certain medications such as Lithium, tricyclic antidepressants, and neuroleptics
and individuals with conditions such as diabetes or retinal degeneration should be
monitored by an ophthalmologist. Because this form of treatment is fairly new, many
doctors recommend a baseline eye exam and annual monitoring.
Humans and animals generally have innate sleep-wake cycles close
to but not exactly 24 hours. They depend on the daily light-dark cycle to keep their
circadian rhythms to a regular 24 hours. If a human is left in a room with no light-dark
cues, he or she will gradually shift into a sleep-wake cycle that is not exactly 24 hours
long. Body temperature and the secretion of the hormone melatonin follow the daily cycle.
Other factors, such as work schedule can modify the sleep-wake cycle in humans. The
autonomous cycle length varies at different periods in the life span. Adolescents often
have an innate cycle longer than 24 hours so that they have the desire to stay up late and
sleep in when it is time to get up. The innate cycle then shifts closer to 24 hours for
adults, but for the elderly, the autonomous sleep-wake cycle may be shorter than 24 hours
resulting in evening tiredness, sleep difficulty and waking too early.
Individuals who have more severe difficulty with the timing of their sleep-wake cycle may
have either Delayed Sleep Phase Disorder (difficulty falling sleep and the urge to sleep
late) or Advanced Sleep Phase Disorder (tiring too early and waking too early) Both
conditions can be treated with bright light. However, the proper timing of the exposure to
light and darkness is more critical than it is for SAD. In these conditions, improperly
timed light and dark exposure can make the problem worse, not better.
In the cases of jet lag or shift work, the individual does not
have a disorder, but is reacting to externally induced changes in the sleep-wake cycle.
Traveling west to east over three or more time zones is the most difficult shift. Large
forced changes in the timing of sleep periods can lead to irritability and decreased
alertness. Many people can deal with this by getting extra rest while traveling or by
switching to a job with a more regular schedule. However, for those who must deal with
frequent sleep timing changes, one may use a special calculator to help determine the
timing for exposure to light and darkness just before and during travel or shift change.
If one calculates the timing wrong, one may actually make the time phase shift worse
instead of better. A travel kit can consist of a calculator, a light visor and
wrap-around dark glasses. Some use small timed doses of Melatonin to achieve the same purpose.
Other uses of bright light therapy
There has been research using light therapy for PMS, obesity and
non-seasonal depression. The results have not been as striking as the results for SAD.
More research needs to be done. However, it may make sense to use light therapy as an
augmentation of other depression treatments or in cases in which the individual is unable
to use other forms of treatment. The study on obesity was small and needs to be repeated
with a larger, more carefully selected group. The obese individuals may have lost weight
because their depression was better. Individuals whose PMS was worse in the winter
responded better to light therapy than individuals with PMS without a seasonal variation.
Winter Blues by Norman Rosenthal 1993, Guilford Press
Seasonal Affective Disorder and Phototherapy edited by Rosenthal and Blehar 1989 Guilford
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