Seasonal affective disorder

Seasonal affective disorder (SAD) is a form of Depression that occurs in relation to the seasons, most commonly beginning in winter.

Causes, incidence, and risk factors

Seasonal affective disorder (SAD) is marked by symptoms of Depression profound enough to seriously affect work and relationship functioning. The disorder may have its onset in adolescence or early adulthood and, like other forms of depression, occurs more frequently in women than in men. Most people with the “winter blahs” or “cabin fever” do not have SAD.

The cause of SAD is not known but is thought to be related to numerous factors such as body temperature, hormone regulation, and ambient light. There is a rare form that occurs in the summer.


  • Depression with a fall or winter onset  
  • Lack of energy  
  • Decreased interest in work or significant activities  
  • Increased appetite with weight gain  
  • Carbohydrate cravings  
  • Increased sleep, excessive daytime sleepiness  
  • Social withdrawal  
  • Afternoon slumps with decreased energy and concentration  
  • Slow, sluggish, lethargic movement

Signs and tests
A psychological evaluation rules out other causes for the symptoms and confirms the diagnosis.


As with other types of depression, antidepressant medications and talk therapy can be effective. Light therapy using a special lamp to mimick the spectrum of light from the sun may also be helpful.

Symptoms commonly resolve on their own with the change of seasons.

Expectations (prognosis)
The outcome is good with continuous treatment, though some people may have the disorder throughout their lives.


Seasonal affective disorder can sometimes progress to a major depressive syndrome.

Calling your health care provider

Call for an appointment with your health care provider if you experience symptoms of seasonal affective disorder.


Individuals who have suffered from recurrent seasonal depression should speak with a mental health care professional to explore preventative treatments.

Provided by ArmMed Media
Revision date: July 7, 2011
Last revised: by Jorge P. Ribeiro, MD