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Seasonal Affective Disorder

 Reviewed by Psychology Today Staff


Seasonal Affective Disorder, or SAD, is a type of recurrent major depressive disorder in which episodes of depression occur during the same season each year. This condition is sometimes called the "winter blues," because the most common seasonal pattern is for depressive episodes to appear in the fall or winter and remit in the spring. Less commonly, SAD occurs as a summer depression, typically beginning in the late spring or early summer and remitting in the fall. SAD may be related to changes in the amount of daylight a person receives.

To be diagnosed with SAD, an individual must meet criteria for major depression coinciding with specific seasons for at least two years. The individual must experience seasonal depressions much more frequently than any non-seasonal depressions.

Seasonal affective disorder is estimated to affect 10 million Americans. Another 10 percent to 20 percent may have mild SAD. SAD is four times more common in women than in men. The age of onset is estimated to be between the age of 18 and 30. Some people experience symptoms severe enough to affect quality of life, and 6 percent require hospitalization. Many people with SAD report at least one close relative with a psychiatric disorder, most frequently a severe depressive disorder (55 percent) or alcohol abuse (34 percent).


Not everyone with SAD has the same symptoms, but, according to the DSM-5, symptoms commonly associated with the winter blues include the following:

  • Feelings of hopelessness and sadness

  • Thoughts of suicide

  • Hypersomnia or a tendency to oversleep

  • A change in appetite, especially a craving for sweet or starchy foods

  • Weight gain

  • A heavy feeling in the arms or legs

  • A drop in energy level

  • Decreased physical activity

  • Fatigue

  • Difficulty concentrating

  • Irritability

  • Increased sensitivity to social rejection

  • Avoidance of social situations

Symptoms of summer SAD are:

Either type of SAD may also include some of the symptoms that occur in major depression, such as feelings of guilt, a loss of interest or pleasure in activities previously enjoyed, ongoing feelings of hopelessness or helplessness, or physical problems such as headaches and stomach aches.

Symptoms of SAD tend to recur at about the same time every year. To be diagnosed with SAD, the changes in mood should not be a direct result of obvious seasonal stressors (like being regularly unemployed during the winter). Usually, this form of depression is mild or moderate. However, some people experience severe symptoms that leave them unable to function in their daily lives.

Seasonal affective disorder can be misdiagnosed as hypothyroidism, hypoglycemia, or a viral infection such as mononucleosis.


The cause for SAD is unknown. There is some evidence that it is related to the body's level of melatonin, a hormone secreted by the pineal gland that regulates the sleep-wake cycle. Darkness stimulates the production of melatonin, preparing the body for sleep. As the winter days get shorter and darker, melatonin production in the body increases and people tend to feel sleepier and more lethargic.

Alternatively, people with SAD may have trouble regulating their levels of serotonin, a neurotransmitter that influences mood. Finally, research has suggested that people with SAD also may produce less Vitamin D in response to sunlight; vitamin D is believed to play a role in serotonin activity. Insufficiency of vitamin D is associated with clinically significant depression symptoms.

There are several factors known to increase an individuals chance of developing SAD. For example, SAD is more frequent in people who live far north or south of the equator. Additionally, people with a family history of other types of depression are more likely to develop SAD than people who do not have such a family history.


Treatment to alleviate the symptoms of SAD typically includes some combination of light therapy, vitamin D supplementation, antidepressant medication, and counseling.

Because winter depression may be a reaction to lack of sunlight, broad-band light therapy is frequently used as a treatment option. This therapy involves exposure to bright artificial light that mimics outdoor light for a period of time in the morning.It requires use of a light box or a light visor worn on the head like a cap. The individual either sits in front of the light box or wears light visor for a certain length of time each day. Generally, light therapy takes between 30 and 60 minutes each day throughout the fall and winter. The exact amount of time varies with each individual. When light therapy is sufficient to reduce symptoms and to increase energy level, the individual continues to use it until enough daylight is available, typically in the springtime. Stopping light therapy too soon can result in a return of symptoms.

When used properly, light therapy has few side effects. The side effects that do arise include eyestrain, headache, fatigue, and irritability. Inability to sleep can occur if light therapy is administered too late in the day. People with a bipolar disorder, skin that is sensitive to light, or medical conditions that make their eyes vulnerable to light damage may not be good candidates for light therapy.

When light therapy does not improve symptoms within a few days, then medication and behavioral therapies such as CBT may be introduced. In some cases, light therapy can be used in combination with one or all of these therapies.

Self-care is an important part of treatment. For those with SAD, it is important to

  • Monitor mood and energy level

  • Take advantage of available sunlight

  • Plan pleasurable activities for the winter season

  • Plan physical activities

  • Approach the winter season with a positive attitude

  • When symptoms develop seek help sooner rather than later

Click here for more information and helpful tips. 

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