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Copyright Dr. R.W. Lam, 2001 - Last revised June/2001
Note that this information does not substitute for medical consultation. You should always check out information with your own physician.
We are unable to answer clinical questions, and we recommend that you contact your family physician or the nearest university medical centre for the name of a mood disorders specialist.
What is SAD? How is it different from the winter blues?
Many people feel mildly “depressed” during the winter, but some people have more severe bouts of feeling down all the time, low energy, problems with sleep and appetite, loss of interest, and reduced concentration to the point where they have difficulty functioning at work or in the home. We say that these people have a clinical depression, to distinguish it from everyday ups and downs. Seasonal affective disorder (“affective” is a psychiatric term for mood), or SAD, describes people who have these clinical depressions only during the autumn and winter seasons. During the spring and summer, they feel well and “normal”.
Other common symptoms of SAD include oversleeping, extreme fatigue, increased appetite with carbohydrate craving, overeating, and weight gain. With more severe episodes, people may have suicidal thoughts.
How common is SAD?
Researchers believe that SAD results from the shorter daylength in winter. Recent studies estimate that SAD is more common in northern countries because the winter day gets shorter as you go farther north. Studies in Ontario suggest that 2% to 3% of the general population have SAD. This means that up to 100,000 people in B.C. may have difficulties in the winter due to significant clinical depression. Another 15% of people have the “winter blahs” – winter symptoms similar to SAD, but not to the point of having a clinical depression.
What treatments are available for SAD?
Research has shown that many patients with SAD improve with exposure to bright, artificial light, called light therapy, or phototherapy. As little as 30 minutes per day of sitting under a special fluorescent light box results in significant improvement in 60% to 70% of SAD patients.
How do you use light therapy?
A fluorescent light box is the best-studied light therapy treatment. Patients usually purchase a lightbox and use it in their own homes. The usual “dose” of light is 10,000 lux, where lux is a measurement of light intensity. Indoor light is usually less than 400 lux; a cloudy day about 3,000 lux; and a sunny day is 50,000 lux or more. Using the light box for about 30 minutes a day is usually enough for a beneficial response.
See our instructions for using a light box.
How do I get a lightbox?
Safe and portable lightboxes are now commercially available. Ask your doctor, or contact our clinic for more information. The cost of a lightbox is usually between $200 and $400 (Cdn). We do not recommend building your own lightbox, because of the safety hazards, and the difficulty in getting the correct dose of light.
Are there side effects to light therapy?
Side effects of light therapy are usually mild. Some people may experience nausea, headaches, eye strain, or feeling “edgy” when they first start using the lightbox. These effects usually get better with time.
There are no known long-term harmful effects of light therapy. However, people with certain medical conditions (such as retinal disease or diabetes) or taking certain medications should have special eye examinations before considering light therapy.
Are there other treatments for SAD?
Other treatments for depression, including the newer antidepressant medications (e.g., selective serotonin reuptake inhibitors, or SSRI’s) are also effective for patients with SAD. Counselling may also help. People with milder symptoms of the “winter blahs” may be helped by simply spending more time outdoors and exercising regularly in the winter (e.g., a daily noon hour walk).
How does light therapy work?
We don’t know, exactly, but research shows that light has a biological effect on brain chemical (neurotransmitters) and function. One theory is that people with SAD have a disturbance in the “biological clock” in the brain that regulates hormones, sleep and mood, so that this clock “runs slow” in the winter. The bright light may help to “reset the clock” and restore normal function. Other theories are that neurotransmitter functions, particularly serotonin and dopamine, are disturbed in SAD, and that these neurotransmitter imbalances are corrected by light therapy and/or antidepressant med-ications. Still other scientists believe that patients with SAD have reduced retinal light sensitivity in the winter that is corrected by light therapy. There is also evidence for a genetic basis for SAD.
What should I do if I think I have SAD?
Everyone who is significantly depressed should be assessed by their family doctor because some physical problems (e.g., thyroid disease) can show up as depression. People with SAD can be treated by their family doctor, referred to a psychiatrist who is aware of SAD. People should not treat themselves with light exposure until after assessment by a qualified health professional.
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Understanding Mental Illness
