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.
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.
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
- Oversleeping or insomnia
- Social withdrawal
- Difficulty concentrating
- Decreased sexual desire
- 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
Light therapy provides a special type of lighting to your body. Therapy includes sitting a few feet away from an ultra-bright light for a certain amount of time each day, usually in the morning. You will be able to read or work during the therapy, as your eyes will remain open. Treatment usually lasts about 30 minutes each day.
There is some evidence that light therapy may be as effective as antidepressant therapy, but with fewer side effects.
Tanning beds are not recommended as a source of light therapy. They give off ultraviolet light, which can increase the risk of cancer. They also have not been proven effective for treating SAD.
Many people find that getting outdoors for a walk each day is also helpful.
Your doctor may prescribe antidepressant medicine or supplements.
Therapists can help you learn ways of managing stress and the symptoms of SAD.
Cognitive-behavior therapy may be used to change your patterns of thinking. This will allow you to notice how you react to symptoms. You will then learn how to change your thinking so that you can react differently. This can decrease the symptoms of SAD.
If you have SAD each year, your doctor may make suggestions to help prevent symptoms. For example, an extended release version of bupropion or light therapy may be used to prevent SAD symptoms from coming if started before depressive symptoms start.
Depression and Bipolar Support Alliance
Mental Health America
Canadian Mental Health Association
Canadian Psychiatric Association
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Seasonal affective disorder. EBSCO DynaMed website. Available at:https://www.dynamed.com/condition/seasonal-affective-disorder. Updated January 17, 2017. Accessed October 4, 2017.
Seasonal affective disorder. Family Doctor—American Academy of Family Physicians website. Available at: https://familydoctor.org/condition/seasonal-affective-disorder. Updated June 2017. Accessed October 4, 2017.
7/20/06 DynaMed Systematic Literature Surveillance.https://www.dynamed.com/condition/seasonal-affective-disorder: Lam RW, Levitt AJ, et al. The Can-SAD study: a randomized controlled trial of the effectiveness of light therapy and fluoxetine in patients with winter seasonal affective disorder. Am J Psychiatry. 2006;163(5):805-812.
2/16/2016 DynaMed Systematic Literature Surveillance.https://www.dynamed.com/condition/seasonal-affective-disorder: Rohan KJ, Mahon JN, et al. Randomized trial of cognitive-behavioral therapy versus light therapy for seasonal affective disorder: acute outcomes. Am J Psychiatry. 2015 Sep 1;172(9):862-869.
Last reviewed September 2018 by EBSCO Medical Review Board Adrian Preda, MD Last Updated: 9/8/2020