What Is Seasonal Affective Disorder (SAD)?

  • Medical Author:
    Roxanne Dryden-Edwards, MD

    Dr. Roxanne Dryden-Edwards is an adult, child, and adolescent psychiatrist. She is a former Chair of the Committee on Developmental Disabilities for the American Psychiatric Association, Assistant Professor of Psychiatry at Johns Hopkins Hospital in Baltimore, Maryland, and Medical Director of the National Center for Children and Families in Bethesda, Maryland.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What causes seasonal affective disorder?

Seasonal affective disorder seems to develop from inadequate bright light during the winter months. Researchers have found that bright light changes the chemicals in the brain. Exactly how this occurs and the details of its effects are being studied. While those specific mechanisms remain undetermined, factors like low vitamin D levels in the blood are found to be associated with a higher occurrence of seasonal affective disorder and some other depressive disorders.

What is the treatment for seasonal affective disorder?

In addition to being key in the prevention of seasonal affective disorder, regular exposure to light that is bright, particularly fluorescent lights, significantly improves depression in people with this disorder when it presents during the fall and winter. The light treatment is used daily in the morning and evening for best results. Temporarily changing locations to a climate that is characterized by bright light (such as the Caribbean) can achieve similar results. Light treatment has also been called phototherapy. Individuals who suffer from seasonal affective disorder will also likely benefit from increased social support during vulnerable times of the year.

Phototherapy is commercially available in the form of light boxes, which are used for approximately 30 minutes daily. The light required must be of sufficient brightness, approximately 25 times as bright as a normal living room light. Contrary to prior theories, the light does not need to be actual daylight from the sun. It seems that it is quantity, not necessarily quality of light that matters in the light therapy of seasonal affective disorder. The most common possible side effects associated with phototherapy include irritability, insomnia, headaches, and eyestrain.

Antidepressant medications, particularly those from the serotonin selective reuptake inhibitor family (SSRI) family, have been found effective treatment for seasonal affective disorder that presents during summer as well as that which tends to occur during the fall or winter. Examples of SSRIs include fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), and citalopram (Celexa). Common side effects for this class of medications include insomnia, nausea, diarrhea, and decreased sex drive or performance. As with any other mood disorder, psychotherapy tends to accentuate the effectiveness of medical treatment and therefore should be included in the approach to addressing this disorder. In individuals who are perhaps vulnerable to the development of bipolar disorder, either light therapy or antidepressant medication can cause a manic episode as a side effect.

Since stimulant medications like modafinil (Provigil) may be a helpful addition to other treatments for seasonal affective disorder, other stimulants like methylphenidate (Ritalin) may play a future role in addressing this disorder. Acupuncture may be a viable alternative intervention to antidepressant medications, particularly in pregnant women, for whom medications should be used with particular caution.

Medically reviewed by Ashraf Ali, MD; American Board of Psychiatry & Neurology with subspecialty in Child & Adolescent Psychiatry


Golden, R.N., B.N. Gaynes, R.D. Ekstrom, et al. "The Efficacy of Light Therapy in the Treatment of Mood Disorders: A Review and Meta-analysis of the Evidence." Am J Psychiatry 162 (2005): 656-662.

Hulisz, Darrell. "Seasonal Affective Disorder." Netwellness. Case Western Reserve University. Feb. 22, 2006.

Kraft, Ulrich. Lighten Up: Seasonal affective disorder-the winter blues-can be lifted with bright light, as long as treatment if timed properly. Scientific American Mind. October 2005.

Lundt, L. "Modafinil Improves Wakefulness and Reduces Fatigue in Patients With Seasonal Affective Disorder/Winter Depression: An Open-Label Study." Sleep 26 (2003): A382.

Manber, R., R.N. Schnyer, J.J. Allen, A.J. Rush, and C.M. Blasey. "Acupuncture: A Promising Treatment for Depression During Pregnancy." J Affect Disord 83.1 Nov. 15, 2004: 89-95.

Murphy, P.K., and C.L. Wagner. "Vitamin D and Mood Disorders Among Women: An Integrative Review." J Midwifery Women's Health 53.5 Sept./Oct. 2008: 440.

Saeed, S.A. and T.J. Bruce. "Seasonal Affective Disorders." American Family Physician 57.6 (1998): 1340-1346.

McMullen, L. (2012). Seasonal affective disorder: don't let it get you down.

McPhee, S. J., & Papadakis, M. A. (2010). Current medical diagnosis & treatment (49th ed.). New York: McGraw Hill

Mental Health America (MHA)
(2013). Seasonal affective disorder (SAD). http://www.nmha.org/go/sad

Medically Reviewed by a Doctor on 6/18/2015

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