Seasonal Affective Disorder (SAD)

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Seasonal affective disorder (SAD) is a mood condition affected by changes in season. It is a type of depression usually linked to fall and winter months, although for a small number of people it can occur in spring and summer. Available treatment options for this condition include light therapy (phototherapy), nutritional changes, and psychotherapy with or without medication.

What Is Seasonal Affective Disorder?

Seasonal affective disorder is usually experienced with the onset of a major depressive episode that is triggered at a specific time of the year. Generally, those affected by SAD report good mental health throughout the rest of the year. Depressive episodes associated with SAD often occur in the fall or winter, but also less commonly in the spring and summer. Other names for SAD are seasonal depression and winter or summer depression (depending on the season in which it occurs).

Seasonal affective disorder was first formally recognized as an adverse state of mental health by the National Institute of Mental Health in 1984. The Diagnostic and Statistical Manual of Mental Disorders (DSM-5) lists it under recurrent major depressive states, but adds a “seasonal pattern” specifier, pointing out that it occurs at a particular time of the year.

Symptoms of Seasonal Affective Disorder

Many people experience a change in mood during the winter as a result of fewer daylight hours, low vitamin D production, and less physical activity. Other people may experience a change in mood in the summer. These temporary states of feeling down in the dumps, however, are not associated with SAD because the symptoms are significantly milder.

The most common symptoms of SAD are similar to the symptoms of major depression. They include:

  • Loss of pleasure or interest in everyday activities
  • Feelings of sadness, despair, worthlessness, or guilt
  • Feeling anxious and overly worried

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  • Increased irritability
  • Tearfulness
  • Increased appetite and weight gain
  • Reduced appetite and weight loss
  • Fatigue
  • Low self-esteem
  • Reduced libido
  • Sleep issues

At the behavioral level, a person experiencing seasonal affective disorder may be less active than usual, avoiding social interactions and activities. He or she may feel excessively sleepy and tired (hypersomnia) for the most of the day. Difficulty with concentration is also very common. A change in appetite may occur, which causes a person to gain or lose weight in an unhealthy way. SAD can affect a person’s social, family, and work life, causing him or her to withdraw from some or all aspects of that part of life.

How Common Is Seasonal Affective Disorder?

According to an article published in the journal Psychiatry, about 10% to 20% of recurrent depressive episodes follow a seasonal pattern. In the United States, the prevalence of seasonal affective disorder varies, often by region. It ranges from 9.7% in New Hampshire to 1.4% in Florida, demonstrating that people living in areas where daylight hours are shorter during winter are more likely to experience this condition. Overall, SAD affects about 6% of Americans, with more women than men experiencing symptoms.

Treatment for Seasonal Affective Disorder

Light therapy, or phototherapy, is a common treatment for SAD. The person in light therapy treatment sits near a light box that mimics natural outdoor light. Light therapy sessions generally last about 10 to 15 minutes at the outset, and gradually increase depending on the severity of a person’s experience with SAD. Although the exact etiology of SAD is still unknown, most researchers believe light therapy reduces a person’s symptoms by balancing the body’s circadian rhythm and increasing the amount of serotonin in the brain, a neurotransmitter that has a direct impact on mood and tends to be reduced in the winter for many people.

Antidepressants are also frequently prescribed to help alleviate severe symptoms of depression and SAD. Many people find lasting results are achieved through participation in psychotherapy, perhaps in combination with medication or light therapy. Cognitive behavioral therapy (CBT), for example, has been shown in some studies to be just as effective as antidepressant medication for treating depression. Therapies like CBT often help people understand and reorganize their thought patterns when living with a condition like SAD or depression, leading to healthier methods of coping than relying on medication alone to treat symptoms.

Tips for Preventing Seasonal Affective Disorder

There are many preventative measures that can help people transition into the winter months without experiencing negative changes in mood. These can include:

  1. Try to spend some time outdoors each day, even on a cloudy day.
  2. Consider investing in a light box to use before the fall and winter months set in, particularly if you have experienced SAD in the past.
  3. Engage in some form of physical activity at least 30 minutes a day, five days a week. Regular exercise helps balance hormones and neurotransmitters that affect your mood.
  4. Maintain an active social life.
  5. Ensure you are getting the foods you need to stay healthy and keep your mood in check. Consider talking to your doctor about checking your nutrition levels to spot any deficiencies that may lead to or exacerbate the symptoms of SAD.
  6. Consider getting involved in a winter sport such as skiing, ice skating, or snowshoeing.
  7. Maintain a regular sleep schedule.
  8. Find a qualified therapist or counselor with whom you can discuss your symptoms and develop a good self-care routine.

SAD in the Summer Months

Although the majority of people who experience SAD find their symptoms worsen in the winter months, a small number of people experience SAD symptoms in the summer. Research on this topic is rather inconclusive, but some studies indicate that longer daylight hours can be disruptive to a person’s circadian rhythm and may cause insomnia, and other studies suggest that seasonal allergies may be the culprit. In addition, the heat of summer can be associated with increased irritability and depressive symptoms for some.

Summer SAD symptoms tend to manifest as agitation, anxiety, irritability, decreased appetite, sleep problems, and feelings of mania. People who experience these symptoms in the summer may benefit from normalizing their sleep schedules, limiting use of stimulants like caffeine and sugar, getting exercise, maintaining social contact, and participating in therapy.

Case Example

  • Winter and depression: Emilia, 41, lives Boston, MA and finds that during the winter her mood tends to plummet and she has difficulty maintaining her energy level. This state usually begins to set in at the end of November and lasts until the end of February. During this period, Emilia constantly feels tired and depressed and wants to curl up and hibernate until winter is over. This fall, however, she decided to seek help when her mood started to change and she learned from a coworker about his experiences with seasonal affective disorder. She found a therapist who spoke with her about the condition and recommended a special light treatment. After three short sessions of light therapy, her physical symptoms started to decrease in severity. From her therapist, she learned how to minimize the effects of SAD on her life and recognize when she has entered a negative thought pattern. Consequently, learning more about the feelings that accompany SAD, as well as how to constructively deal with stress, Emilia is no longer anxious about the forthcoming winter season.


  1. DeAngelis, S. (2006). Promising new treatments for SAD. American Psychological Association. Vol 37, No. 2. Retrieved from
  2. Khazan, Olga. (2014, July 31). When Summer Is Depressing. The Atlantic. Retrieved from
  3. Mayo Clinic. (n.d.). Seasonal affective disorder (SAD). Retrieved from
  4. National Health Service. (2013). Symptoms of seasonal affective disorder. Retrieved from
  5. Roecklein, K.A., and Rohan, K.J. (2005). Seasonal Affective Disorder. Psychiatry (Edgmont). 2(1): 20–26. Retrieved from


Last updated: 07-03-2015

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