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Seasonal Affective Disorder (SAD)

About 11 million Americans have Seasonal Affective Disorder (SAD), a severe form of winter depression that is related to variations of light. SAD was first noted before 1854 but not officially named until the early 1980's.


As seasons change, there is a shift in your circadian rhythm (internal clock) due partly to alterations in sunlight patterns; in the winter months, the days are shorter and darker. The lack of sunlight causes the brain to work overtime producing melatonin, a hormone found in the pineal gland. Melatonin regulates your body clock and sleep patterns. It has also been linked to depression.


  • SAD is typically diagnosed after at least two consecutive years of intense symptoms with a full remission from depression in the spring and summer months.
  • Younger persons are at higher risk but it appears predominantly in women and generally starts in early adulthood.
  • The mood disorder can be felt from October to April. The most difficult months are January and February.
  • Symptoms include: excessive sleeping, overeating/weight gain, a lack of interest in social interactions, a craving for sugary and/or starchy foods, and depressive feelings combined with irritability. Those severely impacted by SAD may also develop suicidal feelings.


  • Get as much sunlight as possible. Light enters the eye, activating the body clock system that is connected to the brain's appetite hardwiring, which explains why you have more food cravings.
  • Spend time outdoors during the day or arrange your home/workplace to receive more sunlight.
  • Phototherapy or bright light therapy has been shown to suppress the brain's secretion of melatonin. The therapy is comprised of an artificial sun box made with special fluorescent tubes that mimic the sun's beneficial rays. 30 minutes of exposure done in the morning keeps the body clock on its springtime cycle, lifting depressive symptoms.
  • One study found that an hour's walk in sunlight was as effective as two and a half hours under bright, artificial light.
  • It is important to note that the gloom caused by winter is biologically felt to some degree by an estimated one in four people. For most, it manifests as winter doldrums that produce mild but manageable sluggishness, food cravings, and a 5-6 pound weight gain. But if your symptoms become severe (as with SAD) and begin to impair daily functioning, consult a physician.

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NIH, National Mental Health Association, Biological Psychology 2nd Edition, Winter Depression Program at New York Psychiatric Institute/Columbia University Medical Center, and Washington and Shady Grove Adventist Hospitals. The Health Tip of the Week is for educational purposes only. For additional information, consult your physician. Please feel free to copy and distribute this health resource.