Skip to main content
Avg ER Wait
Checking ER Wait Time
The feed could not be reached
TriStar Centennial Medical Center

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.
Copyright © Nucleus Medical Media, Inc.


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


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

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.

Antidepressant Medications

Your doctor may prescribe antidepressant medications or supplements.


Therapists can help you learn ways of managing stress and 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.

Revision Information

  • Depression and Bipolar Support Alliance (DBSA)

  • Mental Health America

  • Canadian Mental Health Association

  • Canadian Psychological Association

  • Johansson C, Smedh C, Partonen T, et al. Seasonal affective disorder and serotonin-related polymorphisms. Neurobiol Dis. 2001;8(2):351–357.

  • Mead MN. Benefits of sunlight: a bright spot for human health. Environ Health Perspect. 2008;116(4):A160-A167.

  • Seasonal affective disorder. American Academy of Family Physicians Family Doctor website. Available at: Updated September 2012. Accessed October 12, 2015.

  • Seasonal affective disorder. EBSCO DynaMed website. Available at: Updated December 19, 2012. Accessed October 12, 2015.

  • 7/20/06 DynaMed's Systematic Literature Surveillance. Lam RW, Levitt AJ, Levitan RD, 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.

The health information in this Health Library is provided by a third party. TriStar Health does not in any way create the content of this information. It is provided solely for informational purposes. It does not constitute medical advice and is not intended to be a substitute for proper medical care provided by a physician. Always consult with your doctor for appropriate examinations, treatment, testing, and care recommendations. Do not rely on information on this site as a tool for self-diagnosis. If you have a medical emergency, call 911.