Many individuals experience brief periods of sadness or feeling unlike themselves. Often, these mood shifts coincide with the changing seasons. It’s common to feel “down” or experience the “winter blues” as daylight hours shorten in the fall and winter, with moods improving in the spring as days lengthen. However, sometimes these mood changes are more significant and can affect how a person feels, thinks, and behaves. If you’ve noticed substantial shifts in your mood and behavior with the changing seasons, you might be experiencing seasonal affective disorder (SAD), also known as seasonal depression.
Alt: Woman experiencing seasonal depression near a window, showcasing winter blues.
In most instances, SAD symptoms begin in late fall or early winter and subside during spring and summer – this is known as winter-pattern SAD or winter depression. Conversely, some individuals experience depressive symptoms during the spring and summer months, a condition referred to as summer-pattern SAD or summer depression. Summer-pattern SAD is less prevalent. Understanding What Is Seasonal Depression is crucial for recognizing and addressing this condition effectively.
Signs and Symptoms of Seasonal Depression (SAD)
Seasonal Affective Disorder is characterized by a recurring seasonal pattern of depression, with symptoms typically lasting 4-5 months each year. SAD symptoms include those commonly associated with depression, along with disorder-specific symptoms that differ between winter-pattern and summer-pattern SAD. It’s important to remember that not everyone with seasonal depression will experience all of the symptoms listed below. You can also learn about general signs and symptoms of depression.
General symptoms of depression can include:
- Persistent feelings of sadness, anxiety, or emptiness for most of the day, nearly every day, for at least two weeks
- Feelings of hopelessness or pessimism
- Irritability, frustration, or restlessness
- Feelings of guilt, worthlessness, or helplessness
- Loss of interest or pleasure in hobbies and activities
- Decreased energy, fatigue, or feeling slowed down
- Difficulty concentrating, remembering, or making decisions
- Changes in sleep or appetite or unplanned weight changes
- Physical aches or pains, headaches, cramps, or digestive problems without a clear physical cause that don’t respond to treatment
- Thoughts of death or suicide
For those with winter-pattern SAD, additional symptoms may include:
- Oversleeping (hypersomnia)
- Overeating, especially craving carbohydrates, leading to weight gain
- Social withdrawal (feeling like “hibernating”)
Alt: Individual experiencing winter-pattern SAD, wrapped in a blanket on a couch, demonstrating symptoms like oversleeping and social withdrawal.
For those with summer-pattern SAD, additional symptoms may include:
- Trouble sleeping (insomnia)
- Poor appetite, leading to weight loss
- Restlessness and agitation
- Anxiety
- Violent or aggressive behavior
It’s essential not to confuse winter-pattern SAD with the “holiday blues”—feelings of sadness or anxiety triggered by stresses during specific times of the year. The depression associated with seasonal affective disorder is linked to changes in daylight hours, not the calendar. Stresses related to holidays or predictable seasonal changes in work or school schedules are different from SAD.
Learn about ways to get help and find a healthcare provider or access treatment.
If you or someone you know is struggling or having thoughts of suicide, call or text the 988 Suicide and Crisis Lifeline at 988 or chat at 988lifeline.org. In life-threatening situations, call 911.
The Substance Abuse and Mental Health Services Administration has an online treatment locator to help you find mental health services in your area.
How is Seasonal Affective Disorder Diagnosed?
If you suspect that you or someone you know might be experiencing seasonal depression, it’s crucial to consult with a healthcare provider or mental health specialist to discuss your concerns. They may administer a questionnaire to assess whether your symptoms meet the diagnostic criteria for SAD.
To receive a diagnosis of SAD, a person must meet the following criteria:
- They must exhibit symptoms of depression or the specific symptoms associated with winter- or summer-pattern SAD.
- Their depressive episodes must occur during specific seasons (winter or summer) for at least two consecutive years. Note that not all individuals with seasonal depression experience symptoms every year.
- Depressive episodes during the specific season must be more frequent than depressive episodes experienced at other times of the year.
Who is at Risk of Developing Seasonal Depression?
It’s estimated that millions of Americans experience seasonal depression, although many may not realize they have this common condition. SAD typically begins in young adulthood. What is seasonal depression’s common factor? Location and Sunlight.
SAD is significantly more prevalent in women than in men. Winter-pattern SAD is also more common than summer-pattern SAD. Consequently, seasonal affective disorder is more common in people residing farther north, where winter daylight hours are shorter. For example, individuals in Alaska or New England are more likely to develop SAD than those in Texas or Florida.
Alt: Map of the United States highlighting regions with higher seasonal affective disorder prevalence, particularly in northern states with limited sunlight.
SAD is also more common in individuals with pre-existing conditions such as depression or bipolar disorder, especially bipolar II disorder. Furthermore, people with SAD often have other mental disorders, such as attention-deficit/hyperactivity disorder, eating disorders, anxiety disorders, or panic disorder. Learn more about these disorders.
Seasonal depression can sometimes run in families and may be more common in individuals who have relatives with other mental illnesses, such as depression or schizophrenia.
What Causes Seasonal Affective Disorder?
The exact cause of SAD is still under investigation by researchers. Most research to date has focused on potential causes of winter-pattern SAD because it is more common and easier to study. As a result, less is known about summer-pattern SAD, and further research is needed.
Studies suggest that individuals with SAD, particularly winter-pattern SAD, have reduced levels of the brain chemical serotonin, which helps regulate mood. Research also indicates that sunlight affects levels of molecules that help maintain normal serotonin levels. Shorter daylight hours may prevent these molecules from functioning properly, contributing to decreased serotonin levels in the winter.
Vitamin D deficiency may exacerbate these problems in people with winter-pattern SAD because vitamin D is believed to promote serotonin activity. In addition to vitamin D consumed in food, the body produces vitamin D when exposed to sunlight on the skin. With less daylight in the winter, people with seasonal depression may have lower vitamin D levels, further reducing serotonin activity.
Other studies suggest that both forms of SAD relate to altered levels of melatonin—a hormone important for maintaining the normal sleep−wake cycle. People with winter-pattern SAD produce too much melatonin, which can increase sleepiness and lead to oversleeping.
In contrast, people with summer-pattern SAD may have reduced melatonin levels, consistent with long, hot days worsening sleep quality and leading to depression symptoms. Longer daylight hours, shorter nights, and high temperatures can also cause sleep disruptions. However, these theories have not been systematically tested.
Both serotonin and melatonin help maintain the body’s daily rhythm tied to the seasonal night−day cycle. In people with seasonal depression, changes in serotonin and melatonin disrupt normal daily rhythms. As a result, they can no longer adjust to seasonal changes in day length, leading to sleep, mood, and behavior changes.
Negative thoughts and feelings about the winter or summer and its associated limitations and stresses are also common among people with SAD (as well as others). It is unclear, however, whether these thoughts are causes or effects of the mood disorder, but they can be a useful focus of treatment.
Treatment Options for Seasonal Affective Disorder
Several treatments are available to help individuals cope with seasonal depression. These treatments can be used individually or in combination and fall into four main categories:
- Light therapy
- Psychotherapy
- Antidepressant medication
- Vitamin D
Light therapy and vitamin D are primarily used for winter-pattern SAD, while psychotherapy and antidepressants are used to treat depression in general, including both winter- and summer-pattern SAD. There are currently no treatments specifically tailored to summer-pattern SAD.
Consult with a healthcare provider to discuss the potential benefits and risks of different treatment options and determine which treatment is best suited for your needs. Find tips for talking with a health care provider to improve your care and get the most out of your visit.
Light Therapy
Since the 1980s, light therapy has been a cornerstone treatment for winter-pattern SAD. It involves exposing individuals with SAD to a bright light to compensate for the reduced natural sunlight during darker months.
During this treatment, individuals sit in front of a very bright light box (10,000 lux) every day for about 30-45 minutes, typically first thing in the morning, from fall to spring. The light box, which is approximately 20 times brighter than ordinary indoor light, filters out potentially harmful UV light, making it a safe treatment for most. However, individuals with certain eye diseases or those taking medications that increase sensitivity to sunlight may need alternative treatments or medical supervision during light therapy.
Psychotherapy
Psychotherapy, also known as talk therapy or counseling, can assist individuals with SAD by teaching them new ways of thinking and behaving and modifying habits that contribute to depression.
Cognitive behavioral therapy (CBT) is a type of psychotherapy that helps people challenge and change unhelpful thoughts and behaviors to alleviate depressive and anxious feelings. CBT has been adapted for people with seasonal depression (CBT-SAD). CBT-SAD typically involves two weekly group sessions for six weeks, focusing on replacing negative thoughts related to the season, such as thoughts about the darkness of winter or the heat of summer, with more positive thoughts. CBT-SAD also utilizes behavioral activation, which helps individuals identify and schedule pleasant, engaging indoor or outdoor activities to counter the loss of interest they typically experience in the winter or summer.
Alt: Woman participating in Cognitive Behavioral Therapy (CBT) session to address Seasonal Affective Disorder, focusing on positive thought replacement.
When researchers directly compared CBT-SAD with light therapy, both treatments were equally effective in improving SAD symptoms—although some symptoms improved slightly faster with light therapy than CBT. However, a long-term study that followed SAD patients for two winters found that the positive effects of CBT appeared to last longer.
Learn more about psychotherapy.
Antidepressant Medication
Medications used to treat depression (antidepressants) can be effective for SAD, whether used alone or in combination with talk therapy. Antidepressants work by altering how the brain produces or uses certain chemicals involved in mood or stress regulation.
Antidepressants typically take 4-8 weeks to take effect. Improvements in sleep, appetite, and concentration often occur before mood elevation. It is important to allow the medication sufficient time to work before determining its suitability. You may need to try several medications to find the most effective one.
Because SAD, like other types of depression, is associated with disturbances in serotonin activity, antidepressant medications known as selective serotonin reuptake inhibitors are sometimes used to treat symptoms. These medications can significantly improve a person’s mood.
The U.S. Food and Drug Administration (FDA) has approved an antidepressant called bupropion in an extended-release form designed to last longer in the body. For many people, bupropion can prevent the recurrence of seasonal depressive episodes when taken daily from the fall through early spring.
All medications can have side effects. Consult a healthcare provider before starting or stopping any medication. Learn more about antidepressants. Learn about specific medications like bupropion, including the latest approvals, side effects, warnings, and patient information, on the FDA website.
Vitamin D
Since many individuals with winter-pattern SAD have vitamin D deficiency, vitamin D supplements may help alleviate symptoms. However, studies testing vitamin D as a treatment for seasonal depression have produced mixed results, with some indicating it is as effective as light therapy and others finding no effect.
Discuss any dietary supplements and prescription or over-the-counter medications you are taking with a healthcare provider. Vitamin D can interact with certain medications.
Can Seasonal Affective Disorder Be Prevented?
Given the predictable onset of seasonal depression, individuals with a history of the disorder may benefit from starting the treatments mentioned above before the fall (for winter-pattern SAD) or spring (for summer-pattern SAD) to help prevent or reduce depression symptoms. However, to date, limited studies have investigated whether seasonal affective disorder can be prevented.
It is beneficial to discuss a personalized treatment plan with a healthcare provider. They can help you determine not only the most effective treatment option but also the optimal timing to help prevent SAD depressive episodes.
What are Clinical Trials and Why are They Important?
Clinical trials are research studies that explore new ways to prevent, detect, or treat diseases and conditions. These studies help researchers determine whether a new treatment is safe and effective in people. The primary goal of a clinical trial is to gain new scientific knowledge that can better assist others in the future.
People volunteer for clinical trials for various reasons. Some participate to help doctors and researchers learn more about a disease and improve healthcare. Others, such as those with health conditions, join to try new or advanced treatments that are not widely available.
NIMH supports clinical trials at the National Institutes of Health campus in Bethesda, Maryland, and across the United States. Discuss clinical trials, their benefits, risks, and suitability, with a healthcare provider. Learn more about participating in clinical trials.
For More Information
MedlinePlus (National Library of Medicine) (en español)
ClinicalTrials.gov (en español)
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICESNational Institutes of HealthNIH Publication No. 23-MH-8138Revised 2023
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