Seasonal Affective Disorder

What is seasonal affective disorder?

Seasonal affective disorder (also called SAD) is a type of depression that is triggered by the seasons. The most common type of SAD is called winter-onset depression. Symptoms usually begin in late fall or early winter and go away by summer. A much less common type of SAD, known as summer-onset depression, usually begins in the late spring or early summer and goes away by winter. SAD may be related to changes in the amount of daylight during different times of the year.

How common is SAD?

As many as half a million people in the United States may have winter-onset depression. Another 10% to 20% may experience mild SAD. SAD is more common in women than in men. Although some children and teenagers get SAD, it usually doesn't start in people younger than 20 years of age. For adults, the risk of SAD decreases as they get older. Winter-onset SAD is more common in northern regions, where the winter season is typically longer and more harsh.

What are the symptoms of SAD?

Although your symptoms are clues to the diagnosis, not everyone who has SAD experiences the same symptoms. Common symptoms of winter-onset SAD include the following:
  • A change in appetite, especially a craving for sweet or starchy foods
  • Weight gain
  • A drop in energy level
  • Fatigue
  • A tendency to oversleep
  • Difficulty concentrating
  • Irritability and anxiety
  • Increased sensitivity to social rejection
  • Avoidance of social situations and a loss of interest in the activities you used to enjoy
Symptoms of summer-onset SAD include:
  • A loss of appetite
  • Weight loss
  • Insomnia
  • Irritability and anxiety
  • Agitation
  • Increased sex drive
Either type of SAD may also include some of the symptoms that are present in other forms of depression. These symptoms include feelings of guilt, ongoing feelings of hopelessness and physical problems (such as headaches).

Symptoms of SAD keep coming back year after year. They also tend to come and go at about the same time every year. The changes in mood are not necessarily related to obvious things that would make a certain season stressful (like regularly being unemployed during the winter).

Is there a treatment for SAD?

Yes, treatment is available for SAD. Winter-onset SAD is most likely caused by your body's reaction to the lack of sunlight. Light therapy is one option for treating this type of SAD because increased sunlight can improve symptoms.

If your doctor suggests you try light therapy, you may use a specially made light box, or a light visor that you wear on your head like a cap. You will sit in front of the light box or wear the light visor for a certain length of time each day. Generally, light therapy takes about 30 minutes each day throughout the fall and winter, when you're most likely to be depressed. If light therapy helps, you'll continue it until enough sunlight is available, typically in the springtime. Stopping light therapy too soon can allow the symptoms to come back.

When used properly, light therapy seems to have very few side effects. However, some side effects may include eyestrain, headache, fatigue, irritability and inability to sleep (if light therapy is used too late in the day). Light therapy should be used carefully in people who have manic depressive disorders, skin that is sensitive to sunlight and/or medical conditions that make their eyes vulnerable to sunlight damage.

Tanning beds should not be used to treat SAD. The light sources in tanning beds are high in ultraviolet (UV) rays, which harm both your eyes and your skin.

Your doctor may also want you to try medicine or behavior therapy to treat your SAD. If light therapy or medicine alone doesn't work, your doctor may want you to use them together.

More Information

For more information talk to your doctor.


Written by editorial staff.

American Academy of Family Physicians

Reviewed/Updated: 07/08
Created: 09/00