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.
  • Changes in melatonin levels—Melatonin plays a role in sleep and mood regulation The levels of melatonin in the brain may be affected by the decreased amount of daylight resulting from the change in seasons.
  • Changes in serotonin levels—Serotonin is a melatonin precursor that is also affected by light. It is also known for its role in mood regulation.

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. People with a history of depression or bipolar disorder may experience a seasonal worsening in their depression.


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

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