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Seasonal Affective Disorder (SAD)

Seasonal affective disorder (SAD) is a type of depression that occurs at a certain time of the year, usually in the winter.

Causes, incidence, and risk factors

SAD may begin during the teen years or in adulthood. Like other forms of depression, it occurs more often in women than in men. People who live in places with long winter nights are at greater risk of SAD. A less common form of the disorder involves depression during the summer months.


Symptoms usually build up slowly in the late autumn and winter months. Symptoms are usually the same as with other forms of depression:

  •     Hopelessness
  •     Increased appetite with weight gain (weight loss is more common with other forms of depression)
  •     Increased sleep (too little sleep is more common with other forms of depression)
  •     Less energy and ability to concentrate
  •     Loss of interest in work or other activities
  •     Sluggish movements
  •     Social withdrawal
  •     Unhappiness and irritability

SAD can sometimes become long-term depression. Bipolar disorder or thoughts of suicide are also possible.

Signs and tests

There is no test for SAD. Your health care provider can make a diagnosis by asking about your history of symptoms.

The health care provider may also perform a physical exam and blood tests to rule out other disorders that are similar to SAD.


As with other types of depression, antidepressant medicines and talk therapy can be effective.

Managing Your Depression from Home

To manage your symptoms at home:

  •     Get enough sleep.
  •     Eat a healthy foods.
  •     Take medicines the right way. Ask your health care provider how to manage side effects.
  •     Learn to watch for early signs that your depression is getting worse. Have a plan if it does get worse.
  •     Try to exercise more often. Do activities that make you happy.

Do not use alcohol and illegal drugs. These can make depression worse. They can also affect your judgment about suicide.

When you are struggling with depression, talk about how you are feeling with someone you trust. Try to be around people who are caring and positive. Volunteer or get involved in group activities.

Light Therapy

Your health care provider may prescribe light therapy. Light therapy uses a special lamp with a very bright light that mimics light from the sun.

  • Treatment is started in the fall or early winter, before the symptoms of SAD begin.
  • Follow your health care provider's instructions about how to use light therapy. One way that may be recommended is to sit a couple of feet away from the light box for about 30 minutes each day. This is usually done in the early morning, to mimic sunrise.
  • Keep your eyes open, but do not look straight into the light source. Symptoms of depression should improve within 3 to 4 weeks if light therapy is going to help.

Side effects of light therapy include:

  • Eye strain
  • Headache
  • Mania (rare)

People who take medicines that make them more sensitive to light, such as certain psoriasis drugs, antibiotics, or antipsychotics, should not use light therapy.

A checkup with your eye doctor is recommended before starting treatment.

With no treatment, symptoms usually get better on their own with the change of seasons. Symptoms can improve more quickly with treatment.

Expectations (prognosis)

The outcome is usually good with treatment. Some people, though, have SAD throughout their lives.

Calling your health care provider

Get medical help right away if you have thoughts of hurting yourself or anyone else.


Byrne B, Brainard GC. Seasonal affective disorder and light therapy. Sleep Med Clin. 2008;3:307-315.

Fava M, Cassano P. Mood disorders: major depressive disorder and dysthymic disorder. In: Stern TA, Rosenbaum JF, Fava M, et al., eds.

Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia, PA: Elsevier Mosby; 2008:chap 29

Reviewed by: Fred K. Berger, MD, Addiction and Forensic Psychiatrist, Scripps Memorial Hospital, La Jolla, California. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Black, Stephanie Slon, and Nissi Wang.

PubMed Health:

Reviewed by athealth on February 7, 2014.