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Seasonal Affective Disorder

Seasonal affective disorder (SAD) is a form of depression. It affects people from fall through spring, peaking in January and February. The exact cause is not known, but it appears to be related to hormonal changes that occur with reduced sunlight. Depressive symptoms range from mild to severe. They include increased sleepiness, fatigue, loss of interest in activities, and weight gain.

The main treatment for SAD is light exposure. It is important to get outside during the daylight hours. Some people find using an artificial light box to be helpful. Antidepressants and counseling may be needed if this does not work.

Natural Therapies

There are not many natural therapies used to treat SAD symptoms. A well-balanced diet may be helpful. It should have a healthy mix of fish, dairy, eggs, fruit, and vegetables. These treatments are most effective when used with other treatments.

Possibly Effective

  • Vitamin D is made naturally when skin is exposed to sunlight. Winter season has less sun exposure. This may lead to a drop in vitamin D. Light therapy, regular daylight exercise, and a diet rich in vitamin D can increase the levels. However, there is as yet no conclusive evidence that taking vitamin D supplements effectively treats SAD.A1-A5
  • Negative air ionization therapy (high density) to mimic summer-like conditions B1-B4

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Herbs and Supplements to Be Used With Caution

Talk to your doctor about all herbs or supplements you are taking. Some may interact with your treatment plan or health conditions.



Vitamin D

A1. Gloth FM 3rd, Alam W, Hollis B. Vitamin D vs broad spectrum phototherapy in the treatment of seasonal affective disorder. J Nutr Health Aging. 1999;3(1):5-7.

A2. Penckofer S, Kouba J, Byrn M, Estwing Ferrans C. Vitamin D and depression: where is all the sunshine? Issues Ment Health Nurs. 2010;31(6):385-393.

A3. Kjærgaard M1, Waterloo K, Wang CE, et al. Effect of vitamin D supplement on depression scores in people with low levels of serum 25-hydroxyvitamin D: nested case-control study and randomised clinical trial. Br J Psychiatry. 2012;201(5):360-368.

A4. D. C. Kerr, D. T. Zava, W. T. Piper, S. R. Saturn, B. Frei, and A. F. Gombart, “Associations between vitamin D levels and depressive symptoms in healthy young adult women,” Psychiatry Research, vol. 227, no. 1, pp. 46–51, 2015.

A5. Melrose S. Seasonal affective disorder: an overview of assessment and treatment approaches. Depress Res Treat. 2015;2015:178564.

Negative air ionization therapy

B1. Terman M, Terman JS. Treatment of seasonal affective disorder with a high-output negative ionizer. J Altern Complement Med. 1995;1(1):87-92.

B2. Terman M, Terman JS, Ross DC. A controlled trial of timed bright light and negative air ionization for treatment of winter depression. Arch Gen Psychiatry. 1998;55(10):875-882.

B3. Terman M, Terman JS. Controlled trial of naturalistic dawn simulation and negative air ionization for seasonal affective disorder. Am J Psychiatry. 2006;163(12):2126-2133.

B4. Harmer CJ, Charles M, McTavish S, Favaron E, Cowen PJ. Negative ion treatment increases positive emotional processing in seasonal affective disorder. Psychol Med. 2012;42(8):1605-1612.

Vitamin B12

C1. Oren DA1, Teicher MH, Schwartz PJ, et al. A controlled trial of cyanocobalamin (vitamin B12) in the treatment of winter seasonal affective disorder. J Affect Disord. 1994;32(3):197-200.

C2. Almeida OP1, Ford AH1, Hirani V1, et al. B vitamins to enhance treatment response to antidepressants in middle-aged and older adults: results from the B-VITAGE randomised, double-blind, placebo-controlled trial. Br J Psychiatry. 2014;205(6):450-457.

C3. Almeida OP1, Ford AH1, Flicker L1. Systematic review and meta-analysis of randomized placebo-controlled trials of folate and vitamin B12 for depression. Int Psychogeriatr. 2015;27(5):727-737.


D1. Rosenthal NE, Sack DA, Jacobsen FM, et al. Melatonin in seasonal affective disorder and phototherapy. J Neural Transm Suppl. 1986;21:257-267.

D2. Wirz-Justice A, Graw P, Krauchi K, et al. Morning or night-time melatonin is ineffective in seasonal affective disorder. J Psychiatr Res. 1990;24:129–137.

D3. Lewy AJ, Bauer VK, Cutler NL, Sack RL. Melatonin treatment of winter depression: a pilot study. Psychiatry Res. 1998;77:57–61.

D4. Leppämäki S, Partonen T, Vakkuri O, Lönnqvist J, Partinen M, Laudon M. Effect of controlled-release melatonin on sleep quality, mood, and quality of life in subjects with seasonal or weather-associated changes in mood and behaviour. Eur Neuropsychopharmacol. 2003;13(3):137-145.

D5. Hansen MV, Danielsen AK, Hageman I, Rosenberg J, Gögenur I. The therapeutic or prophylactic effect of exogenous melatonin against depression and depressive symptoms: a systematic review and meta-analysis. Eur Neuropsychopharmacol. 2014;24(11):1719-1728.

Last reviewed February 2019 by EBSCO NAT Review Board Richard Glickman-Simon, MD