Seasonal Affective Disorder: Winter Depression

Seasonal Affective Disorder and Light Therapy


1.What is SAD?

2.Incidence of SAD and relation to latitude

3.Theories about how light

affects mood and sleep

4.How we use the light box

5.Other treatments for SAD

6.Side effects of light therapy

7.Sleep disorders

8.Jet lag and shift work

9.Other uses of bright light therapy

10.Other issues

What is SAD?

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)

Epidemiology of SAD

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.

Theories about how light

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.

How the Light Box is used

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

the treatment.

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.

Other treatments

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.

Sleep Disorders

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.

Jet Lag and Shift Work

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


Copyright 2002

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