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Seasonal Affective Disorder (SAD)

Seasonal affective disorder is a form of depression also known as SAD, seasonal depression or winter depression. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-5-TR), this disorder is identified as a type of depression – major depressive disorder with seasonal pattern.

People with SAD experience mood changes and symptoms similar to depression. The symptoms usually occur during the fall and winter months when there is less sunlight and usually improve with the arrival of spring. The most difficult months for people with SAD in the United States tend to be January and February. While it is much less common, some people may experience SAD in the summer.

SAD is more than just “winter blues.” The symptoms can be distressing and overwhelming and can interfere with daily functioning. However, it can be treated. About 5% of adults in the U.S. experience SAD and it typically lasts about 40% of the year. The prevalence of SAD varies with geographical latitude, age and sex. The prevalence increases at higher latitudes with SAD being more common in people living far from the equator where there are fewer daylight hours in the winter. Younger people and women are also at higher risk. 

SAD has been linked to changes in the brain prompted by shorter daylight hours and less sunlight in winter. As seasons change, people experience a shift in their biological internal clock or circadian rhythm that can cause them to be out of step with their daily schedule.

Symptoms and Treatment

Common symptoms of SAD include fatigue, even with too much sleep, and weight gain associated with overeating and carbohydrate cravings. SAD symptoms can vary from mild to severe and can include many symptoms similar to major depression, such as:

  • Feeling sad or having a depressed mood.
  • Loss of interest or pleasure in activities previously enjoyed.
  • Changes in appetite; usually eating more and craving carbohydrates.
  • Change in sleep; usually sleeping too much.
  • Loss of energy or increased fatigue despite increased sleep hours.
  • Increase in purposeless physical activity (e.g., inability to sit still, pacing, handwringing) or slowed movements or speech (these actions must be severe enough to be observable to others).
  • Feeling worthless or guilty.
  • Difficulty thinking, concentrating, or making decisions.
  • Thoughts of death or suicide.

SAD may begin at any age, but it typically starts when a person is between ages 18 and 30.


SAD can be effectively treated in several ways, including light therapy, antidepressant medications, talk therapy or some combination of these. While symptoms will generally improve on their own with the change of season, symptoms can improve more quickly with treatment, especially if they have become severe.

Light therapy involves sitting in front of a light therapy box that emits a very bright light (and filters out harmful ultraviolet (UV) rays). It usually requires 20 minutes or more per day, typically first thing in the morning, during the winter months. Most people see some improvements from light therapy within one or two weeks of beginning treatment. To maintain the benefits and prevent relapse, treatment is usually continued through the winter. Because of the anticipated return of symptoms in late fall, some people may begin light therapy in early fall to prevent symptoms.

Talk therapy, particularly cognitive behavior therapy (CBT), can effectively treat SAD. Selective serotonin reuptake inhibitors (SSRIs) are the antidepressants most commonly used to treat SAD.

For some people, increased exposure to sunlight can help improve symptoms of SAD. For example, spending time outside or arranging your home or office so that you are exposed to a window during the day. (However, exposure to UV light from the sun can increase your risk of skin cancer.and you should talk with your physician about risks and benefits of direct sunlight exposure int he prevention and treatment of SAD.) Taking care of your general health and wellness can also help—regular exercise, healthy eating, getting enough sleep, and staying active and connected (such as volunteering, participating in group activities and getting together with friends and family) can help.

If you feel you have symptoms of SAD, seek the help of a trained medical professional. Just as with other forms of depression, it is important to make sure there is no other medical condition causing your symptoms. SAD can be misdiagnosed in the presence of hypothyroidism, hypoglycemia, infectious mononucleosis, and other viral infections, so proper evaluation is key. A mental health professional can diagnose the condition and discuss therapy options. With the right treatment, SAD can be a manageable condition.

If you feel your depression is severe or if you are experiencing suicidal thoughts, consult a physician immediately or seek help at the closest emergency room. The 988 Suicide & Crisis Lifeline provides 24/7, free and confidential support for people in distress as well as prevention and crisis resources for you or your loved ones. Call or text 988, or chat

Physician Review

Felix Torres, M.D., MBA, FACHE, DFAPA, CCHP-MH

March 2024

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