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Seasonal Affective Disorder (SAD)

Reviewed by: HU Medical Review Board | Last reviewed: October 2023

As the seasons change, many people experience changes in their mood and energy levels. But for some, this natural ebb and flow can take a more severe form called seasonal affective disorder (SAD).1-3

SAD is a type of depression that occurs only during specific seasons, most often in the fall and winter. When the days become shorter and there are fewer daylight hours, some people feel down and depressed. Once the spring arrives and the days are longer, symptoms go away. This is called winter-pattern SAD, or winter depression.1-3

Summer-pattern SAD is when depressive symptoms occur during the spring and summer. This type of SAD is more rare than winter depression.1-3

No matter what kind of SAD you have, this type of depression can affect your daily life. It may make it difficult to function at the level you are used to.1-3

Who gets SAD?

SAD can affect anyone of any age. But it is more common among adults over age 20. Where you live can make a difference as well. SAD is more common in people who live farther north – for example, in Alaska – where the days are much shorter during the winter.1-3

There are several risk factors that may make someone more likely to develop SAD, including:1-3

  • Gender – SAD is more common in women than in men
  • Personal history of mood disorders
  • Family history of mental health issues

What causes SAD?

Experts believe that a primary cause of SAD is a lack of sunlight during the shorter days of fall and winter. This reduced exposure to natural light can affect the production of certain chemicals in the brain, like serotonin and melatonin.1-3

Another possible cause relates to the body’s circadian rhythm, or internal clock. This clock regulates sleep-wake cycles. A change in the seasons can disrupt this cycle, which can affect sleep patterns and mood.1-3

What are the symptoms of SAD?

The symptoms of seasonal affective disorder can vary in severity. Some people have mild symptoms. Others have symptoms that make it hard to complete daily tasks.1-3

Symptoms of SAD include:1-3

  • Depressed mood that lasts for most or all of the day, nearly every day
  • Decreased interest or pleasure in activities once enjoyed
  • Overeating and weight gain or poor appetite
  • Difficulty concentrating and making decisions
  • Social withdrawal
  • Irritability
  • Fatigue and low energy
  • Oversleeping and trouble waking up in the morning
  • A heavy feeling in the arms or legs

How is SAD diagnosed?

For a diagnosis of SAD, symptoms must occur seasonally for at least 2 years in a row, and they must greatly interfere with daily life. Other medical conditions and mood disorders must also be ruled out. A doctor or mental health specialist will typically perform a physical exam, detailed medical history, and mental health assessment to make a diagnosis.1,2

How is SAD treated?

Seasonal affective disorder is very treatable. While everyone is different, there are several approaches that may be effective.

Light therapy (phototherapy)

Light therapy, also known as phototherapy, uses a special lightbox that provides daily exposure to bright light. This type of light mimics natural sunlight. It helps regulate circadian rhythms and improve mood. It is a common and effective option for those with SAD.1-4
There are many lightboxes on the market. Ask your doctor which one they recommend.


Cognitive behavioral therapy (CBT) and other forms of psychotherapy can help people learn how to manage their symptoms, change negative thought patterns, and develop coping strategies for SAD.1-4

Prescription drugs

In some cases, doctors may prescribe antidepressant medicine to help manage SAD symptoms. Selective serotonin reuptake inhibitors (SSRIs) are commonly used.1-4

Vitamin D

Many people with SAD also have low levels of vitamin D. In these cases, doctors may prescribe a vitamin D supplement. But research to understand the link between vitamin D deficiency and SAD is ongoing. It is possible to take too much vitamin D. Talk to your healthcare provider about whether a vitamin D supplement is right for you and how much they recommend.1-4

Lifestyle changes

Simple lifestyle changes also may help reduce SAD symptoms. These changes include keeping a regular sleep schedule, exercising regularly, and managing stress. Relaxation techniques like meditation and yoga can be effective ways to manage stress.1-4


Self-care practices can make a significant difference in managing SAD. Good methods of self-care include eating a healthy diet, staying socially connected, mindfulness, and spending time outdoors when possible.1-4

SAD is temporary

Seasonal affective disorder affects many people during the fall and winter months. But with proper treatment, you can manage your symptoms and enjoy a better quality of life, even when the sun is less visible.

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