Seasonal Affective Disorder

Seasonal Affective Disorder (SAD), condition in which people experience episodes of depression that typically begin each fall or winter and lift in the spring.

In some cases, people rebounding from winter depression veer to the opposite mood extreme and experience mania.

Bipolar disorder, characterized by mood swings between depression and mania, may also follow a seasonal pattern.

The prevalence of seasonal affective disorder varies by latitude, with occurrences increasing at higher latitudes.

Thus in North America, the disorder is much more common in Canada, where it affects nearly 10 percent of people, than in Florida, where it affects 1 to 2 percent of people.

Many other people experience milder seasonal changes in their mood, sleep habits, weight, energy level, and social activity.

Seasonal affective disorder accounts for 5 to 10 percent of cases of major depression (severe depression).

Young people have a higher risk of developing the disorder than older people, and women have a higher risk than men.

Symptoms
People with seasonal affective disorder usually experience their first episode of depression in their 20s or 30s.

Like all depressed people, they feel either intensely unhappy or profoundly indifferent to people, work, and activities that once brought them pleasure.

They think slowly and have poor concentration.

Those with severe depression may complain of feeling incompetent or immoral and may behave in irrational and bizarre ways.

People with the winter form of seasonal affective disorder usually have an increased appetite, weight gain, and a craving for foods high in carbohydrates, including chocolate or other sweets.

They sleep many more hours than normal and become sluggish and socially withdrawn.

People with the summer form of seasonal affective disorder often have a decreased appetite with weight loss, sleep fewer hours than normal, wake up depressed, and feel restless and fidgety.

Causes
Seasonal affective disorder appears to result from lack of sufficient light.

Research shows that depression more frequently affects people living in low-light conditions. For example, people living at higher latitudes, where winter days are dark and short, have higher rates of the disorder than those living at lower latitudes.

In addition, increased exposure to light often helps people with seasonal affective disorder, but not those with other forms of depression.

Along with light, genetic factors seem to play an important role in explaining why only some people develop the disorder. For example, 60 percent of seasonal affective disorder sufferers have close relatives who suffer from a form of depression, either seasonal or nonseasonal.

Another theory is that people with SAD have an abnormal circadian (daily) rhythm, which produces fatigue and sluggishness during the day ( Biological Clocks).

In addition, some studies have linked the disorder with abnormally low concentrations of serotonin, a neurotransmitter in the brain.

Treatment
Light therapy, repeated exposure to bright light, helps about 75 percent of people with seasonal affective disorder, especially those who oversleep, crave carbohydrates, and feel worse in the evening.

Light therapy involves sitting in front of a high-intensity light box or wearing a light visor for at least 30 minutes a day.

The treatment usually produces benefits within the first week.

Some studies have shown that exposing sleeping SAD patients to low levels of light in the early morning—creating an “artificial dawn”—can help lift depression.

Standard antidepressant medications, such as fluoxetine (Prozac) and sertraline (Zoloft), appear to be as effective as light therapy for treating seasonal affective disorder.

Doctors also recommend exercise, stress management, and exposure to outdoor light.