Seasonal affective disorder (SAD) is a form of depression most often associated with the lack of daylight in extreme northern and southern latitudes from the late fall to the early spring.
Although researchers are not certain what causes seasonal affective disorder, they suspect that it has something to do with the hormone melatonin. Melatonin is thought to play an active role in regulating the "internal body clock," which dictates when humans feel like going to bed at night and getting up in the morning. Although seasonal affective disorder is most common when light is low, it may occur in the spring, and it is then often called reverse SAD.
Causes & symptoms
The body produces more melatonin at night than during the day, and scientists believe it helps people feel sleepy at nighttime. There is also more melatonin in the body during winter, when the days are shorter. Some researchers believe that excessive melatonin release during winter in people with SAD may account for their feelings of drowsiness or depression. One variation on this idea is that, during winter, people's internal clocks may become out of sync with the light-dark cycle, leading to a long-term disruption in melatonin release.
Seasonal affective disorder, while not an official category of mental illness listed by the American Psychiatric Association, is estimated to affect 10 million Americans, most of whom are women. Another 25 million Americans may have a mild form of SAD, sometimes called the "winter blues" or "winter blahs." The risk of SAD increases the further from the equator a person lives.
The symptoms of SAD are similar to those of other forms of depression. People with SAD may feel sad, irritable, or tired, and may find themselves sleeping too much. They may also lose interest in normal or pleasurable activities (including sex), become withdrawn, crave carbohydrates, and gain weight.
Doctors usually diagnose seasonal affective disorder based on the patient's description of symptoms, including the time of year they occur.
The first-line treatment for seasonal affective disorder is light therapy, exposing the patient to bright artificial light to compensate for the gloominess of winter. Light therapy uses a device called a light box, which contains a set of fluorescent or incandescent lights in front of a reflector. Typically, the patient sits for 30 minutes next to a 10,000-lux box (which is about 50 times as bright as ordinary indoor light). Light therapy appears to be safe for most people. However, it may be harmful for those with eye diseases. The most common side effects are vision problems such as eye strain, headaches, irritability, and insomnia. In addition, hypomania (elevated or expansive mood, characterized by hyperactivity and inflated self esteem) may occasionally occur.
Recently, researchers have begun testing whether people who do not completely respond to light therapy can benefit from tiny doses of the hormone melatonin to reset the body's internal clock. Early results look promising, but the potential benefits must be confirmed in larger studies before this type of treatment becomes widely accepted.
Like other types of mood disorders, seasonal affective disorder may also respond to medication and psychotherapy. The four different classes of drugs used for mood disorders are:
- Heterocyclic antidepressants (HCAs), such as amitriptyline (Elavil).
- Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft).
- Monoamine oxidase inhibitors (MAO inhibitors), such as phenelzine sulfate (Nardil) and tranylcypromine sulfate (Parnate).
- Lithium salts, such as lithium carbonate (Eskalith), often used in people with bipolar mood disorders, are often useful with SAD patients. Many SAD patients also suffer from bipolar disorder (excessive mood swings; formerly known as manic depression).
A number of psychotherapy approaches are useful as well. Interpersonal psychotherapy helps patients recognize how their mood disorder and their interpersonal relationships interact. Cognitive-behavioral therapy explores how the patient's view of the world may be affecting mood and outlook.
Most patients with seasonal affective disorder respond to light therapy and/or antidepressant drugs.
- Cognitive behavioral therapy
- Psychotherapy aimed at helping people change their attitudes, perceptions, and patterns of thinking.
- A naturally occurring hormone involved in regulating the body's "internal clock."
- A chemical messenger in the brain thought to play a role in regulating mood.
For Your Information
- Peters, Celeste A. Don't Be SAD: Your Guide to Conquering Seasonal Affective Disorder. Calgary, Alberta: Good Health Books, 1994.
- Anderson, Janis L., and Gabrielle I. Warner. "Seasonal Depression." Harvard Health Letter (February 1996): 7-8.
- "Winter Depression: Seeing the Light." The University of California Berkeley Wellness Letter (November 1996): 4.
- American Psychiatric Association. 1400 K Street NW, Washington, DC 20005. (202) 682-6000. http://www.psych.org.
- National Depressive and Manic Depressive Association. 730 N. Franklin Street, Ste. 501, Chicago, IL 60610. (312) 642-0049.
- National Institute of Mental Health. Mental Health Public Inquiries, 5600 Fishers Lane, Room 15C-05, Rockville, MD 20857. (301) 443-4513. (888) 826-9438. http://www.nimh.nih.gov.
Gale Encyclopedia of Medicine. Gale Research, 1999.