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A. Definition

  1. Depression developing during autumn or winter
  2. Depression remitting in spring or summer
  3. This cycle occurs for at least 2 successive years
  4. "Summer" SAD also described, but very uncommon
  5. ICD-10 Research Diagnostic Criteria
    1. Three or more episodes of affective disorder for 3 or more consecutive years
    2. Onsets and remissions within a particular 90-day period of the year
    3. Seasonal episodes substantially outnumber non-seasonal episodes
  6. SAD is a form of bipolar affective or recurrent depressive disorder
    1. SAD with minor depression is more common amongst women
    2. SAD with major depression is more common amongst men
    3. Uncommon in children and elderly
  7. Lifetime prevalance of SAD is probably ~1%

B. Pathogenesis

  1. Unclear etiology
  2. Reduced daylight period likely contributes
  3. Bright light treatment may improve symptoms
  4. However, unclear that reduced light itself is the problem
  5. Decreased availability of dopamine in ocular neurons has been found
  6. Impaired transmission of neuropeptide Y and serotonin to circadian pacemaker implicated
  7. Disturbed serotonergic activity implicated in winter SAD
  8. Unclear if specific serotonin receptor subsystems are responsible
  9. Some data suggest increased risk of SAD with specific serotonin transporter mutations
  10. Reduced norepinephrine, cortisol, and growth hormone responses to serotonin agents
  11. Melatonin production and function appears to be normal in SAD

C. Symptoms and Signs

  1. Social withdrawal, decreased activity, sadness, anxiety
  2. Decreased libido, poor sleep quality, irritability, carbohydrate craving, weight increase
  3. Suicidal thoughts are uncommon
  4. Decreased weight is infrequent

D. Treatment

  1. Similar to other forms of depressive and affective disorder
  2. However, bright-light treatment is recommended first line treatment for winter SAD
    1. Best treatments use 2500 lux artificial light for 2 hours in morning
    2. Higher intensities for shorter exposures (10,000 lux for 30 minutes) equally effective
    3. Light response ~80%
  3. Antidepressants are effective in SAD
    1. Sertraline (Zoloft®)
    2. Fluoxetine (Prozac®)
    3. Moclobemide, an MAO inhibitor, was not effective
  4. Bright light treatment may be combined with antidepressants

References

  1. Partonen T and Lonnqvist J. 1998. Lancet. 352(9317):1369