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Symptoms and Signs of Seasonal Depression (SAD)

Doctor's Notes on Seasonal Depression (SAD)

Seasonal Affective Disorder (SAD, Seasonal Depression) is a type of depression that is linked to the seasons of the year. The majority of people that have SAD have symptoms mainly in the late fall and winter seasons (a few have summer SAD) and is most common in young adult women. Signs and symptoms may include depressed mood, fatigue, loss of interest in activities, feelings of worthlessness or hopelessness, poor concentration, indecisive and thoughts of death or suicide. These occur at about the same time each year for the individual; some experience anxiety anticipating the seasonal changes and their returning symptoms. People with winter SAD may also exhibit excess sleeping, craving for sugar, starchy foods or alcohol, weight gain, heaviness in arms and legs, have social conflicts and behavioral changes. Other signs and symptoms of summer SAD include insomnia, poor appetite, weight loss, agitation and anxiety.

The exact causes of SAD are unknown. However, SAD may run in families and may be related to alcohol abuse, and low levels of vitamin D. Some researchers believe chemical changes occur in the brain when sunlight is reduced or increased as seasons change.

Medical Author:
Medically Reviewed on 3/11/2019

Seasonal Depression (SAD) Symptoms

Seasonal affective disorder (SAD) may have some of the same signs and symptoms as other types of depression. The stress of anticipating the onset of SAD often results in the sufferer having anxiety months before SAD symptoms begin each year.

  • Most people have only some of these symptoms, not all.
    • Depressed mood
    • Loss of interest in usually enjoyable activities
    • Fatigue or loss of energy
    • Feelings of worthlessness or hopelessness
    • Poor concentration, indecisiveness
    • Recurrent thoughts of death or suicide
  • The symptoms of SAD come back every year, and for any specific person, they tend to come and go at about the same time each year.
  • Winter SAD is typically characterized by
    • sleeping more than usual;
    • craving for sugar, starchy foods, or alcohol;
    • weight gain;
    • irritability;
    • conflicts with other people;
    • heaviness of arms and legs;
    • behavior disturbances (in children).
  • People with winter SAD may seek out light places or sunlight, or like to have lots of artificial lights on.
  • Summer SAD is generally accompanied by some of the following signs and symptoms:

Seasonal Depression (SAD) Causes

The exact causes of seasonal affective disorder (SAD) are unknown.

  • Chemical changes in the brain caused by changes in the amount of sunlight are probably involved. Risk factors for SAD include living in geographical locations that are dark or cloudy during the winter.
  • A tendency to have SAD may run in some families.
  • Given how often alcohol abuse and dependence occur in individuals with SAD, there is thought to be a possible genetic link between having either illness.
  • Low levels of vitamin D seem to be a risk factor for developing a number of mood disorders, including SAD.

Learn to Spot Depression Symptoms, Warning Signs, Medication Slideshow

Learn to Spot Depression Symptoms, Warning Signs, Medication Slideshow

While everyone feels sad from time to time, if that occurs most days for more than two weeks, it could mean that clinical depression is occurring. Major depression is a period of sadness, irritability, or low motivation that occurs with other symptoms, lasts at least two weeks in a row, and is severe enough to negatively affect one's life. Depression is not a sign of weakness or a character flaw. It is a real and treatable medical illness.

These PET scans of the brain indicate low activity in a person suffering from depression compared to someone who is not depressed.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.