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.
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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.
Last reviewedSeptember 2013by Michael Woods, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.