SAD (Seasonal Affective Disorder)

Seasonal affective disorder (SAD) is episodes of depression that occur at a certain time of the year, usually during winter.

Causes, incidence, and risk factors

The disorder may begin during the teen years or in early 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 for SAD. A less common form of the disorder involves depression during the summer months.

Other factors that may make SAD more likely include:

  • Amount of light
  • Body temperature
  • Genes
  • Hormones


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

  • Increased appetite with weight gain (weight loss is more common with other forms of depression)
  • Increased sleep and daytime sleepiness (too little sleep is more common with other forms of depression)
  • Less energy and ability to concentrate in the afternoon
  • Loss of interest in work or other activities
  • Slow, sluggish, lethargic movement
  • Social withdrawal
  • Unhappiness and irritability

Signs and tests

There is no real 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 medications and talk therapy can be effective. Taking long walks during the daylight hours and getting exercise can make the symptoms better. Keep active socially, even if it involves some effort.

Light therapy using a special lamp with a very bright fluorescent light (10,000 lux) that mimics light from the sun may also be helpful.

  • Follow your doctor’s instructions about how to use light therapy. A common practice is to sit a couple of feet away from the light box for about 30 minutes every 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 – 4 weeks if light therapy is going to help.

Side effects of light therapy include:

  • Eye strain and headache
  • Mania

People who take drugs that make them more sensitive to light, such as certain psoriasis drugs, antibiotics, or antipsychotics, should avoid light therapy. A check-up with your eye doctor is recommended before starting treatment.

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

Expectations (prognosis)

The outcome is good with treatment. However, some people have the disorder throughout their lives.


Seasonal affective disorder can sometimes become long-term depression. Bipolar disorder or ideas of suicide are also possible.

Calling your health care provider

Call for an appointment with your health care provider if you have symptoms of seasonal affective disorder. Get help right away if you have thoughts of hurting yourself or anyone else.


People who have had repeated seasonal depression should talk to a mental health care professional about prevention methods. Starting treatment during the fall or early winter, before the symptoms of SAD begin, may be helpful.

Article taken in part from


All content on this website is provided for general information only, and should not be treated as a substitute for the medical advice of your own doctor or any other health care professional. Always consult your own GP if you’re in any way concerned about your health.

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