Seasonal Affective Disorder



Seasonal affective disorder (SAD) is a type of depression. It is associated with the seasonal changes in light. SAD most commonly occurs in late fall and lasts through the winter and into spring. SAD is more than feeling down, it interferes with normal daily functions during these times.
Brain—Psychological Organ
Brain face skull
SAD may be caused by fluctuations in hormones and brain chemicals.
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The causes of SAD are not completely clear. Some factors that may play a role include:
  • Reduced sunlight—This affects internal clocks, readjusting hormones and brain chemicals.
  • Increase in melatonin production—Melatonin may cause symptoms of depression. This hormone is produced in higher amounts in the dark.
  • Low serotonin—Serotonin is a brain chemical that is associated with well-being. In people with SAD, there may be a lack of serotonin in the brain.

Risk Factors

SAD is more common in women than in men, often appearing in young adulthood. People who live in northern latitudes also have an increased risk of developing SAD.


Symptoms appear and peak during the winter months. As spring and summer approach, symptoms disappear. SAD may cause:
  • Depressed mood, feelings of sadness
  • Fatigue/lack of energy
  • Irritability
  • Oversleeping or insomnia
  • Social withdrawal
  • Difficulty concentrating
  • Decreased sexual desire
  • Overeating
  • Weight gain
  • Cravings for sweet or starchy foods


The doctor will ask about your symptoms and medical history. A physical and psychological exam will be done.A diagnosis of SAD will only be made if you have some of the symptoms above and:
  • Your symptoms have occurred annually for at least 2 years
  • No nonseasonal major depressive episodes have occurred during same period
  • You have complete relief from symptoms during the summer months

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