What is Seasonal Affective Disorderolder woman sitting alone

  • “SAD, also referred to as winter or seasonal depression, is a syndrome with depression that starts and ends at the same time each year.” (®)
  • Also known as “cabin fever during the winter months” (Mayo Clinic), “winter depression or winter blues” (Wikipedia), and “winter blahs” (U.S. National Institute of Health).

When does it start?

  • sad or depressed girl“It usually happens during the winter. A less common type of SAD happens in the summer.” (U.S. National Institute of Health)
  • “During the fall and winter months, some people suffer from symptoms of depression that can appear gradually or come on all at once. These symptoms often dissipate as spring arrives and stay in remission through the summer months. For some people, this is a sign that they suffer from SAD.” (American Psychiatric Association)

Who is most likely to be affected?

  • “The disorder may have its onset in adolescence or early adulthood and, like other forms of depression, occurs more frequently in women than in men. Most people with the ‘winter blahs’ or ‘cabin fever’ do not have SAD.” (U.S. National Institute of Health)
  • “Because the lack of daylight during wintertime is related to SAD, it is seldom found in countries within 30 degrees of the equator, where the sun shines year round.” (®)

What causes SAD?sad teenage girl

  • “Winter depression is probably caused by your body’s reaction to a lack of sunlight.” (
  • “Just as sunlight affects the seasonal activities of animals, SAD may be an effect of this seasonal light variation in humans. As seasons change, people experience a shift in their biological internal clock or circadian rhythm that can cause them to be out of step with their daily schedule.” (American Psychiatric Association)
  • “There are two types of SAD: fall-onset SAD and summer-onset SAD. The fall-onset type, often called “winter depression,” is more recognized. With less sunlight during these two seasons, the brain does not produce enough serotonin, the soothing neurotransmitter in the brain. This results in feelings of depression.” (®)

How common is it?

  • “It is measurably present at latitudes in the Arctic region, such as Finland (64° 00′ N) where the rate of SAD is 9.5%. Cloud cover may contribute to the negative effects of SAD … Norman Rosenthal, a pioneer in SAD research, has estimated that the prevalence of SAD in the adult United States population is between about 1.5 percent (in Florida) and about 9 percent (in the northern US).” (Wikipedia)
  • “The National Institutes of Health estimates that more than 36 million Americans suffer seasonal depression that occurs in the fall.” (®)

What are the treatments?

What are the symptoms?

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