What is Seasonal Affective Disorder (SAD)?

Posted Jan 5, 2012 | Posted in Diseases & Treatments

Seasonal affective disorder, also referred to as SAD, is a type of depression that occurs at a certain time of year. For most people who suffer from seasonal affective disorder, symptoms usually begin in the fall and continue through winter. Although less common, the condition can occur in the summer, and is often referred to as reverse seasonal affective disorder. Originally identified by Norman E. Rosenthal in 1984, SAD is now recognized as a common disorder, and, according to the Diagnostic and Statistical Manual of Mental Disorders,  can be found in up to 10 percent of the population in some regions of the U.S.

Causes & Risk Factors

Although SAD can affect anyone, there are certain risk factors that may increase the probability. Seasonal affective disorder is more common in women than in men and typically affects those between the ages of 15 and 55. People living in areas that experience dramatic changes in seasonal daylight — with shorter days and longer nights — are also at greater risk for SAD.  Lack of light may disrupt your body’s circadian rhythms (your body’s inner clock), and has the potential to interfere with serotonin levels, which play a large role in a person’s mood. It’s also thought that genetics play a role in this disorder, as people that have close-relatives afflicted with seasonal affective disorder are more likely to be affected themselves.


For most people, SAD symptoms start around September and end between April and May. Symptoms of SAD are usually very similar to those associated with depression, and may include:

  • Increased appetite, carbohydrate cravings and weight gain
  • Increased sleep
  • Decreased energy and feelings of lethargy
  • Decreased ability to concentrate later in the day
  • Decreased interest in socialization and day-to-day activities
  • A general sense of unhappiness and enhanced irritability


Diagnosing seasonal affective disorder can be difficult because of the similarity to nonseasonal depression. To determine if someone is suffering from SAD, a doctor will usually ask the following questions:

  • Have you experienced depression during a certain time of the year for at least two years in a row?
  • Do your symptoms recede as the season ends?
  • Do you have symptoms associated with SAD, such as carbohydrate cravings, weight gain and general lack of energy?
  • Do you have a close relative who has has had SAD?


Light therapy has proven to be an effective form of treatment for SAD, with some patients experiencing relief within the first week of treatment. To ensure continual improvement, light therapy needs to take place every day until the season ends. There are two specific types of light treatment: bright light treatment and dawn simulation. With bright light treatmenta patient sits in front of a light box, typically in the morning, for at least an hour. Dawn simulation treatment uses a dim light of slowly increasing intensity to simulate a sunrise while a person sleeps. Additional treatments may include antidepressants and counseling, which can help a person learn more about seasonal affective disorder and how best the manage their symptoms.


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