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Seasonal Affective Disorder

Seasonal Affective Disorder

Seasonal affective disorder (SAD) is a type of depression with a recurring seasonal pattern, with symptoms most often starting in the late fall and early winter and going away in the spring and summer. The risk of SAD is higher in people who live far from the equator and those with a personal or family history of depression. Women are more likely than men to develop SAD, and younger people have a higher risk than older ones.

Types of treatment that have been studied for SAD include medication (antidepressants), psychotherapy (such as cognitive behavioral therapy, CBT), light therapy, and dietary supplements (such as vitamin D).

Bottom Line

  • Antidepressant medications, including selective serotonin reuptake inhibitors (SSRIs) or bupropion, may be used for SAD.
  • A type of CBT adapted for use with SAD patients helps to relieve symptoms, and its effects may continue into subsequent winters, even without additional sessions with a therapist.
  • Light therapy involves daily exposure to bright artificial light, usually from early fall until spring. It typically requires sitting for 20 to 60 minutes each morning in front of a light box that produces much more light than ordinary indoor lighting. The idea behind light therapy is to replace the diminished sunlight of the fall and winter months. In several studies, light therapy has had beneficial effects on SAD symptoms similar to those of medication or CBT.
  • Low levels of vitamin D, caused by low dietary intake of the vitamin or not enough exposure to sunshine, have been found in people with SAD. However, it’s unclear whether vitamin D supplementation can help to relieve SAD symptoms.
  • Very little research has been done on dietary supplements other than vitamin D for SAD. A few studies involving very small numbers of people have looked at melatonin and St. John’s wort for treatment of SAD, with unclear or inconsistent results. Single small studies of vitamin B12 for treatment of SAD and Ginkgo biloba for prevention of SAD did not find that the supplements were beneficial.


  • Like other medications, those used for SAD may have side effects. Sometimes, it’s necessary to try several medications to identify one that works well without too many undesired effects.
  • CBT is generally considered safe.
  • Light therapy sometimes has side effects such as dizziness, nausea, headaches, or tired eyes. This form of treatment may not be appropriate for people with diseases of the retina, recent eye surgery, or bipolar disorder or those who are taking medicines that increase sensitivity to light.
  • Some dietary supplements may have side effects or interact with medicines. St. John’s wort is known to interact in harmful ways with a large number of medicines. Some vitamins, including vitamin D, may be toxic if taken in excessive doses. It’s a good idea to talk with your health care provider about any dietary supplement you’re considering or taking, especially if you take medicine.

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Last Updated: June 2019