Seasonal affective disorder

Seasonal affective disorder (SAD) is a depressive disorder most often associated with the lack of daylight in extreme northern and southern latitudes fromthe late fall to the early spring. Although researchers are not certain whatcauses seasonal affective disorder, they suspect that it has something to dowith the hormone melatonin. Melatonin is thought to play an active role in regulating the body's circadian rhythm, or "internal 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.

The body produces more melatonin at night than during the day, and scientistsbelieve 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 illnesslisted 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. Peoplewith SAD may feel sad, irritable, or tired, and may find themselves sleepingtoo 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 They may also lose interest in normal or pleasurable activities (including sex), become withdrawn, crave carbohydrates, and gain weight.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-linetreatment for seasonal affective disorder is phototherapy, 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, characterizedby hyperactivity and inflated self esteem) may occasionally occur.

Recently, researchers have begun testing whether people who do not completelyrespond 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 usedfor mood disorders are:

  • Heterocyclic antidepressants (HCAs), such asamitriptyline (Elavil).
  • Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft).
  • Monoamine oxidase inhibitors (MAO inhibitors), such as phenelzinesulfate (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.

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