12/10/2013 10:36 am ET Updated Jan 25, 2014

QUIZ: How Much Do You Know About Seasonal Affective Disorder?

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Seasonal affective disorder, or SAD, is a form of depression related to the seasons, very often winter when sunlight is at a minimum. Though many of its symptoms -- sadness, fatigue and changes in weight or sleep patterns -- are similar to those of depression, SAD symptoms tend to appear as the seasons change. As many as 6 percent of people in the United States have this type of seasonal depression, with about 10 to 20 percent more experiencing a less severe form, known as the winter blues. But there's a ray of hope for people with SAD: steps to help prevent it and ways to treat SAD symptoms.

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