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Seasonal Affective Disorder

Not Just Another Winter Mood Change


Updated December 17, 2009

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

As the days shorten, the weather gets brisk and winter settles in, you may hear some people complain of seasonal affective disorder (SAD). You may even wonder if it is affecting you.

Seasonal affective disorder has become a bit of a household name, and some people may use it to describe what is simply winter doldrums. Many people feel less than themselves this time of year, the degree of which certainly varies. But it's when that depression is severe enough that it interferes with daily life that it truly is seasonal affective disorder.

What may surprise you is that according to the diagnostic guidelines, seasonal affective disorder is either a type of major depressive disorder or a type of depressive episode of bipolar disorder (either bipolar I or bipolar II disorder).

What Exactly Is Seasonal Affective Disorder?

Seasonal affective disorder is a type of depression that starts and stops in a pattern that's linked to changes of season. The most common pattern is that of winter depression, where symptoms begin in the fall and let up in the spring. However, some individuals experience a start of symptoms in the spring.

Here's what goes into a diagnosis of SAD:

For the last two years:

  • There has been a pattern of depression occurring with a change of season.

  • These depressive episodes either lifted with the next change of season, or switched to mania or hypomania.

  • There were no other major depressive episodes during the period -- only the seasonal ones.
Also, during the person's lifetime, there must have been many more season-related depressive episodes than episodes not related to seasonal changes.

Finally, the seasonal depression can't be related to another psychological or social stress that always occurs during the season in question. Examples of this might include being a landscaper who's out of work each December, or coping with the memories of a loved one who died in the winter.

An individual who experiences mania, and who also regularly has major depressive episodes during the winter (but rarely other times of the year), would have bipolar I disorder and seasonal affective disorder.

Someone who has never had mania or hypomania but who does experience severe depression during the winter would have a clinical diagnosis of major depressive disorder classified as seasonal affective disorder.

Seasonal Affective Disorder Symptoms

For someone with bipolar disorder, the symptoms of SAD can include any of the symptoms of a major depressive episode. Some of these are:
  • Low energy
  • Difficulty getting up in the morning
  • Sleeping more than usual
  • Loss of productivity
  • Weight gain
  • Craving for carbohydrates and sugar
  • Depression
  • Irritability
For a complete list, see Major Depressive Episode.

Causes of Seasonal Affective Disorder

There is still a great deal of research that needs to be done in this area. However, the bulk of literature on this topic agrees that for winter SAD, there is a distinct link to daylight. The symptoms of SAD increase as the days shorten and the number of hours of daylight decrease.

The amount of light we are exposed to influences the regulation of the brain chemicals serotonin and melatonin. Disruption in these systems has been associated with mood symptoms.

Treatment of SAD

Whether the seasonal affective disorder is associated with bipolar disorder or major depression, the first line of treatment is the same: light therapy (phototherapy).

Light therapy involves exposure to bright light one or two times a day for sessions ranging from 10 to 45 minutes. This therapy is most effective if the first session is done in the morning. Many people begin to have some relief within as little as a week.

Antidepressant medications may be prescribed along with or in place of light therapy. Exercise is also encouraged as well as limiting carbohydrates, sugar and caffeine.


Seasonal Affective Disorders. Priory.com. Jan 2001. 9 Dec 2009.

Q&A: Light Therapy. Columbia University. 9 Dec 2009.

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