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Biology 202
2003 Second Web Paper
On Serendip

Feeling SAD? Let There Be Light!

Rachel Singer

It's wintertime, and you are gathered for the holidays with all of your family and friends. Everything seems like it should be perfect, yet you are feeling very distressed, lethargic and disconnected from everything and everyone around you. "Perhaps it is just the winter blues," you tell yourself as you delve into the holiday feast, aiming straight for the sugary fruitcake before collapsing from exhaustion. However, the depression and other symptoms that you feel continue to persist from the beginning of winter until the springtime, for years upon end without ceasing. Although you may be tempted to believe that you, like many millions of other Americans, are afflicted with a case of the winter blues, you are most likely suffering from a more severe form of seasonal depression known as Seasonal Affective Disorder, or SAD. This form of depression has been described as a form of a unipolar or bipolar mood disorder which, unlike other forms of depression, follows a strictly seasonal pattern. (5).

During the winter, many of us suffer from "the winter blues", a less severe form of seasonal depression than SAD. Still others are sufferers have an already existent condition, such as pre-menstrual syndrome or depression, which is exacerbated by the coming of the winter. (2). In general, many people suffer from some form of sporadic depression during the wintertime. We may feel more tired and sad at times. We may even gain some weight or have trouble getting out of bed. Over 10 million people in America, however, may feel a more extreme form of these symptoms. They may constantly feel lethargic and depressed to an extent that social and work related activities are negatively affected. This more extreme form of the "winter blues" is SAD. Typical SAD symptoms include sugar cravings, lethargy, depression, an increase in body weight, and a greater need for sleep (1). Onset of these symptoms usually occurs in October or November, and the symptoms disappear in early spring. Frequently, people who suffer from SAD react strongly to variations in the amount of light in their surrounding environment. Most often, patients who suffer from SAD and live at more northern latitudes note that the more north they live, the more distinct and severe their SAD symptoms become. In addition, SAD patients note that their depressive symptoms increase in severity when the amount of light indoors decreases and the weather is cloudy. (4). Most commonly, symptoms of SAD appear in one's late twenties or thirties, yet the disorder has been less frequently diagnosed in children. Out of all of the patients who suffer from SAD, 70-80% are female. (1).

Multiple theories exist as to the origins of SAD. The exact cause is currently unknown, yet doctors believe that stress, heredity and the chemical makeup of the body all play a role in its initiation. A strongly-held belief is that the lack of presence of sufficient sunlight can lead to the disorder. Simply being in a room without windows for an extended period of time can trigger a depressive episode in SAD patients. The body's circadian rhythms, which regulate an individual's daily sleep-wake cycles, are disturbed when sunlight is not as prevalent. This is the reason why individuals with wintertime SAD often experience a difficulty in waking up in the morning during the longer nights of winter. (3). In addition, a disruption of the body's circadian rhythms is known to be a likely cause of depression. (6). Thus, during the wintertime months or time spent in a dark room, when the circadian rhythms can potentially be disrupted, a person who suffers from SAD may experience severe depressive episodes.

Scientists have also hypothesized that the disorder could be due to a decrease in serotonin, a key neurotransmitter in the brain. When the brain is deficient of serotonin, depression has been known to result. The production of serotonin has been thought to be caused by the presence of sunlight; people with SAD who suffer from depression have been found to have lower serotonin levels in their brain. In addition, research has found that SAD could also be due to an increase in the level of melatonin, a hormone which is connected to sleep. (3). The higher level of this hormone in SAD patients during the lengthier periods of darkness during winter have also been thought to be linked to their depressive symptoms. Although SAD is most commonly seen during the winter, the condition can also occur during the summer months. These patients plan trips to colder climates during the winter to relieve their depression. This rarer form of seasonal depression causes symptoms such as agitation, loss of weight, inability to sleep, anxiety and a loss of appetite.

Apparently, in patients who suffer from the more common winter form of SAD, an increase in the amount of time per day in which the sky is dark is thought to be one of the main causes of depressive symptoms. According to Dr. Daniel Kripke, a psychiatry professor at the University of California San Diego, the photoperiod of reduced light during the wintertime is a result of the reduced daylight, and that many mammals' seasonal responses are dominated by this photoperiod. Kripke explained that the mammals whose seasonal responses were dominated by the shorter photoperiod in winter experienced a change in appetite and lethargy during the winter. So naturally, it would seem reasonable that one of the main proposed treatments for SAD (aside from medication and psychotherapy, which have been proven to be effective) is an added source of light during the longer periods of darkness which occur during the wintertime. In fact, multiple tests conducted in Japan, the United States and Europe from 1986 through 1995 have shown that a strong light source proves highly effective in treating both nonseasonal and seasonal forms of depression. (6). In this form of SAD treatment, the light, which is between 10 and 20 times stronger than a regular room light, is placed several feet from the patient. The patient sits in front of this light in the morning (so as not to induce insomnia, which nighttime light therapy may cause) for at least a half a hour. (3). Side effects are minimal, and the treatment is very simple to undergo.

Although multiple light sources can be used in the treatment of SAD, one must be careful in choosing the proper kind of light therapy, which will not only be effective for use but safe for use as well. For example, in a 1992 study by Lam et al., tests were conducted in an effort to see which wavelengths of light were most efficacious in the treatment of SAD patients. It turned out that the UV wavelength of around 300 nm was not at all helpful in the treatment of seasonal depressive disorder. In addition, this low wavelength can cause harmful burns, as we all know from spending long days in the sun at the beach. Filters for certain wavelength —emitting light therapy devices should be used in order to prevent wavelengths which are below 400 nm from being emitted (5). In addition, full spectrum light used in rooms has not been efficacious in the treatment of SAD. The light used in treatment must be of higher intensity, at least ten to twenty times stronger than a typical light bulb used in a room. (2). Neither UV light nor full spectrum light should be used in the treatment of SAD; both have proven to be ineffective during light therapy trials.

Even though neither the full spectrum lights nor the 300 nm UV-emitting therapy device was effective in treating SAD patients, forms used with the special wavelength filter are safe and have proven to be very useful in the treatment of SAD. Most often, high-intensity light boxes which do not emit UV wavelengths have been used to treat the symptoms. Depending on the individual, smaller or larger lux (a measure of illumination) light boxes can be used. A normal light bulb emits somewhere between 200-500 lux. SAD patients may select a very high lux light box which emits10,000 lux, and requires a shorter amount of therapy time. Other patients prefer a weaker lux box (minimum of 2500 lux required), yet these boxes require a longer time spent in front of the light box. (1).

In addition, light visors (which also emit high-intensity luxes of light) are available, and are worn by the SAD patient. The visors are advantageous to patients who do not wish to sit idly in front of a light box for a half an hour or more; treatment can be administered while the patient is in motion. Also, a special dawn simulator can be used. This very strong light is placed beside the patient's bed, and its intensity is slowly augmented so as to reach its greatest strength when the patient is set to wake up. 1992-1993 studies conducted in Seattle by Avery et al. (where the sky is frequently overcast in the winter) have shown the dawn simulators to be highly effective. (6). In fact, the improvement was described by the Seattle study group as significant even when the final lux emission amount was as small as 250 lux!

The only rare side effects seen from the forms of light therapy used have been eye strain, nausea, irritability and headaches, and these often subside as the patient gets acclimated to the therapy. (4). Outdoor light, which provides just as much light as the light boxes (even when the sky is cloudy) has also been shown to improve SAD symptoms. SAD symptoms have been ameliorated in patients who took a daily 60-minute walk.

Many millions of Americans suffer from depression during the winter. However, a fascinating and often neglected fact is that those ten million who are afflicted with the more severe symptoms seen in SAD may suffer because of a simple deficiency in the amount of light present during the winter! Their brains may react in response, and a disruption of circadian rhythms, decrease in serotonin, and an increase in melatonin can result. As a consequence of these reactions in the brain due to the lack of light, the SAD patient can become severely depressed. So while trying to light up the lives of family members and friends with SAD through encouragement, please inform them about the many types of light therapy which are currently available — both you and the SAD patient will be glad that you did.


1)Seasonal Affective Disorder, From Northern County Psychiatric Associates of MD

2)Information and Frequently asked Questions about Seasonal Affective Disorder, From PhoThera Light Products

3)Seasonal Affective Disorder, From Mayo Clinic

4)Seasonal Affective Disorder, From Nation's Voice on Mental Illness

5)Seasonal Affective Disorder, from

6)Light Treatment for Nonseasonal Depression, from Psychiatric Times

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