What is seasonal affective disorder (SAD)?

Seasonal affective disorder (SAD) is a depression that occurs during a particular season of the year. Most people with SAD are depressed during the fall and winter, when the days are shortest. Their depression disappears in the spring and summer. A less common type begins in late spring or early summer. Changes in the amount of daylight may be the cause of SAD.

Although many people say they get the "blues" in the winter, a person with SAD has much more difficulty coping during this season. Like other forms of depression, SAD interferes with daily life. Overcast days can make a person with SAD feel worse. People with SAD have mild to moderate depression.

SAD can affect anyone, but women and adolescents seem to be more susceptible; older adults are less likely to develop it. It is more common in northern latitudes. SAD sufferers also tend to have a family member with mental illness, such as depression or alcohol abuse.

Varying levels of the neurotransmitter serotonin are believed to play a role in SAD. The sleep hormone melatonin, which has been linked to depression, also may play a role. The body makes more melatonin in the dark. So, the shorter, grayer days of winter boost levels of melatonin.

The symptoms of SAD can be confused with symptoms of other illnesses, including hypothyroidism and viral infections such as mononucleosis.

Someone with a mild case of SAD can ease symptoms by adding more daylight to daily activities. Spending time outdoors each day and getting regular outdoor exercise are two effective methods to combat SAD. For more severe cases, doctors may prescribe light therapy and possibly antidepressants. Light therapy involves using a full-spectrum fluorescent light for a certain amount of time each morning.