Tuesday, 18 September 2007


Seasonal Affective Disorder and Light Therapy

What is seasonal affective disorder?
Seasonal affective disorder is a major (serious) form of depression that occurs at the same time each year. Researchers have identified two types of SAD. The most common type, known as "winter depression," usually begins in the late fall to early winter months and ends in spring. Seasonal affective disorder can also occur in the summer (known as "summer depression").

Surveys estimate that 4 to 6 percent of the general population experience SAD. Women with SAD outnumber men four to one. The disorder usually begins in person's early twenties and the risk for developing SAD decreases with age (Saeed and Bruce).

What are the symptoms of seasonal affective disorder?
People who suffer from SAD can have the common symptoms of depression such as sadness, anxiety, lost of interest in usual activities, withdrawal from social activities, and an inability to concentrate. Symptoms most common to winter depression include:
• Increased sleep
• Increased appetite
• Weight gain
• Irritability
• Interpersonal difficulties (especially feelings of rejection)
• A heavy leaden feeling in the arms and legs

How is seasonal affective disorder diagnosed?
Physicians can diagnose SAD based on criteria (a set of standards) developed by the American Psychiatric Association. Your physician can determine if you are suffering from depression and if this depression is a seasonal affective disorder. Tables 1 and 2 below list the criteria used for diagnosing a depressive episode and SAD.

What causes SAD?
The exact cause of SAD is unknown, but researchers suspect changes in the availability of sunlight plays an important role. Statistics show that winter depression becomes increasingly more common the farther people live north or south of the equator. Episodes of winter depression also tend to be longer and more severe at higher latitudes (Saeed and Bruce).

How is seasonal affective disorder different from the "holiday blues?"
Many people use the expression "holiday blues" to refer to a sadness or depression occurring during winter or the holiday season. This term should be differentiated from SAD. The holiday blues are related to psychosocial factors such as increased family obligations, isolation, decreased exercise, expectations that one "should" feel good, or association of the holidays with early memories and possible unresolved childhood conflicts.

In contrast, SAD is a subtype of a major depressive disorder (or bipolar disorder) with seasonal patterns and appears to be more biological in origin. (Rosenthal).

How is winter depression treated?
Research now shows that light therapy, or exposure to light, is an effective treatment for winter depression. Light therapy is administered by a 10,000-lux light box, which contains white fluorescent light tubes covered with a plastic screen that blocks ultraviolet rays. Full-spectrum light is not necessary (Saeed and Bruce).

The patient sits in front of the box with his or her eyes open, but should not look directly into the light. The therapy begins with daily sessions of 10 to 15 minutes, which are gradually increased to 30 to 45 minute sessions. Ninety minutes of exposure per day is often prescribed. The therapy typically continues until spring.


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