Seasonal Affective Disorder

Seasonal Affective Disorder is a topic covered in the 5-Minute Clinical Consult.

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  • Seasonal affective disorder (SAD) is a heterogeneous mood disorder with depressive episodes usually occurring in winter months, with full remissions in the spring and summer.
  • Ranges from a milder form (winter blues) to a seriously disabling illness
  • Must separate out patients with other mood disorders (such as major depressive disorder and bipolar affective disorder) whose symptoms persist during spring and summer months


  • Affects up to 500,000 people every winter
  • Up to 30% of patients visiting a primary care physician (PCP) during winter may report winter depressive symptoms.
  • Predominant age: occurs at any age; peaks in 20s and 30s
  • Predominant sex: female > male (3:1)

  • 1–9% of the general population
  • 10–20% of patients identified as having mood symptoms will have a seasonal component.

Etiology and Pathophysiology

The major theories currently involve the interplay of phase-shifted circadian rhythms, genetic vulnerability, and serotonin dysregulation.

  • Melatonin produced by the pineal gland at increased levels in the dark has been linked to depressive symptoms; light therapy on the retina acts to inhibit melatonin secretion.
  • Serotonin dysregulation, because it is secreted less during winter months, must be present for light therapy to work, and treatment with SSRIs appears to reverse SAD symptoms.
  • Decreased levels of vitamin D, often occurring during low-light winter months, may be associated with depressive episodes in some individuals experiencing SAD symptoms.
  • Some twin studies and a preliminary study on GPR50 melatonin receptor variants have suggested a genetic component.
  • Recent studies indicate an association with the melanopsin gene (OPN4).
  • Increased incidence of depression, ADHD, and alcoholism in close relatives

Risk Factors

  • Most common during months of January and February: Patients frequently visit PCP during winter months complaining of recurrent flu, chronic fatigue, and unexplained weight gain.
  • Working in a building without windows or other environment without exposure to sunlight

General Prevention

  • Consider use of light therapy at start of winter (if prior episodes begin in October), increase time outside during daylight, or move to a more southern location.
  • Bupropion (Wellbutrin) is an FDA-approved antidepressant for the prevention of SAD.

Commonly Associated Conditions

Some individuals with SAD have a weakened immune system and may be more vulnerable to infections.

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