Seasonal affective disorder (SAD) is a type of depression that occurs around the same time each year, usually beginning and ending during a specific season. SAD affects millions of people. For some individuals, it's a mild case of the "winter blues," but for many, SAD is severe and needs treatment to improve.1-7 If you suffer from SAD, there's no need to tough it out until the season changes. Instead, learn how SAD might affect you and try the following tactics to feel better.

SAD Is Related to Changes in Seasons

Seasonal affective disorder most commonly hits as the seasons shift to colder months, but it can also affect people in summer. In most cases, SAD symptoms appear during late fall or early winter and go away during the sunnier days of spring and summer. Less commonly, people with the opposite pattern have symptoms that begin in spring or summer. Longer days and increasing heat and humidity might play a role in summer SAD. In either case, symptoms might start out mild but become more severe as the season progresses.1-7

The most common symptoms of SAD are similar to depression and include:1-3,5,6

  • Feeling listless, sad, or down most of the day, nearly every day
  • Losing interest in activities you once enjoyed
  • Having low energy and feeling sluggish
  • Having difficulty concentrating
  • Feeling hopeless, worthless, or guilty
  • Having thoughts of not wanting to live

Additional symptoms typical of winter-onset SAD include:2,3,6,7

  • Oversleeping
  • Overeating, especially with a craving for high-carbohydrate foods
  • Weight gain
  • Tiredness or low energy

Additional symptoms typical of summer-onset SAD include:2,3,7

  • Trouble sleeping (insomnia)
  • Poor appetite
  • Weight loss
  • Being irritable, anxious, or agitated

What Causes SAD?

Although the specific cause of seasonal affective disorder is unknown, some factors that might come into play include:2

  • Circadian rhythm (your “biological clock”). The reduced level of sunlight in fall and winter might cause winter-onset SAD. This decrease in sunlight might disrupt your body's internal clock, leading to feelings of depression.2,3,7
  • Serotonin level. A decrease in serotonin might play a role in SAD. Reduced sunlight can cause a drop in serotonin that might trigger depression.2,6,7
  • Melatonin level. The change in season can disrupt the balance of the body's level of melatonin, which plays a role in sleep patterns and mood.2,7,8

Who Is Affected by SAD?

Seasonal affective disorder occurs more often in women than in men and more frequently in younger adults than in older adults. Factors that can increase your risk of SAD include:1-3,6-8

  1. Living further from the equator. SAD is more common among people who live further north or south of the equator. This might be due to decreased sunlight during the winter months and longer days during the summer months.1-3,7,8
  2. History of mood disorders. Symptoms of depression might worsen seasonally if you have major depression or bipolar disorder. SAD might occur more often if you currently experience anxiety or panic disorder. And having blood relatives with SAD or another form of depression can also increase your risk of SAD.1,2,7
  3. Low vitamin D. Some vitamin D is produced in the skin when it's exposed to sunlight. Vitamin D helps boost serotonin activity  ̶  a brain chemical that affects mood. Less sunlight and not getting enough vitamin D from foods and other sources might result in low levels of vitamin D in the body.2,7,9

How to Find Out if You Have SAD

It's not unusual to feel gloomy or down on occasion. But if these feelings last for days at a time and you can't get motivated to participate in activities that you usually enjoy, then see your health care professional. This is especially important if your sleep patterns and appetite have changed, you turn to alcohol or drugs for comfort or relaxation, or you feel hopeless or think about suicide.2-6

To determine if you have seasonal affective disorder, your doctor will do a physical exam and take a thorough health history. Your practitioner will ask about your symptoms, thoughts, feelings, and behavior patterns.3,6

How to Improve Symptoms of SAD

Some individuals find it helpful to begin treatment before symptoms of seasonal affective disorder typically start and continue treatment past the time that symptoms normally go away. Others need continuous treatment to prevent symptoms from returning.2,3,6,7

Light Therapy

Light therapy is a primary treatment for fall-onset SAD. In light therapy, also called phototherapy, you sit a few feet from a special light box so that you're exposed to bright light within the first hour of waking up each day. Light therapy mimics natural outdoor light and appears to cause a change in brain chemicals linked to mood.2,3,5-7,9

  • A randomized controlled trial of 57 participants with SAD found that symptoms decreased by more than 40 percent after exposure to four weeks of bright white or dim red light.9
  • Another study with 98 participants examined the effect of light therapy and exercise on depressive symptoms. Researchers found that both treatments, even in combination, were well tolerated and effective for reducing symptoms.9

Although it's not clear why, not every person with SAD responds to light therapy. In addition, you might not be a candidate for light therapy if you take certain medications or have specific eye or other health conditions. For example, light therapy might induce mania in patients with unrecognized or undertreated bipolar disorder.

There are important safety and health factors to consider before purchasing a light box. Talk to an expert about the best light box for you that is effective and safe.2,7,9 To learn more about light therapy for SAD, read: Choosing a Light Therapy Box.  


Psychotherapy, also called talk therapy, is another option for treating SAD. A type of psychotherapy called cognitive behavioral therapy (CBT) is often used to help individuals manage their symptoms.2-8 CBT is an effective tool that helps you become aware of inaccurate or negative thinking so you can view challenging or stressful situations more clearly and respond to them in a more effective way. 

Traditional cognitive behavioral therapy has been adapted to use with SAD (CBT-SAD). In addition to incorporating CBT tactics of replacing negative thoughts with more positive ones, CBT-SAD uses a process called behavioral activation. This process helps you identify and schedule pleasant, engaging indoor or outdoor activities to combat the loss of interest you might experience when suffering from SAD. 


Some people with SAD benefit from antidepressant treatment. Keep in mind that it might take several weeks to notice the full benefits of an antidepressant. In addition, you might have to try different medications before you find one that works well for you and has the fewest side effects.2,3,5-7

Complementary or Alternative Medicine

Certain herbal remedies and supplements, such as melatonin, vitamin D, and St. John’s Wort, are sometimes used to relieve depression symptoms, although results of clinical studies are mixed.2,7-9

How to Keep Mood and Motivation Steady Throughout the Year

If seasonal change gets you down, in addition to following a treatment plan from your health professional, there are things you can do to manage SAD and feel better.

  • Make your environment sunnier and brighter. Open blinds, trim tree branches that block sunlight or add skylights to your home. Sit closer to bright windows while at home or in the office.3,4,7
  • Get outside. Take a long walk, eat lunch at a nearby park, or simply sit on a bench and soak up the sun. Even on cold or cloudy days, outdoor light can help – especially if you spend some time outside within two hours of getting up in the morning.3,4,7
  • Exercise regularly. Exercise and other types of physical activity help relieve stress and anxiety, both of which can increase SAD symptoms. Being more fit can make you feel better about yourself, too, which can lift your mood.3,4,6,7,11
  • Adopt regular sleep habits. Schedule reliable times to wake up and go to bed each day. Get enough sleep to feel rested. Reduce or eliminate napping and oversleeping if you experience SAD in the fall or winter.3,7,11
  • Make healthy choices. Choose healthy foods for meals and snacks. Don't turn to alcohol or recreational drugs for relief.3,4
  • Practice stress management. Learn techniques to manage your stress. You might try relaxation techniques such as yoga, tai chi, and meditation. Unmanaged stress can lead to depression, overeating, or other unhealthy thoughts and behaviors.8,10
  • Socialize. When a person feels down, it can be hard to socialize, so make an effort to connect with individuals who you enjoy being around. They can offer support, be a shoulder to cry on, or share a laugh to give you a boost.3,4,11
  • Take a trip.        If it’s possible, then take winter vacations in sunny, warm locations if you have winter SAD or to cooler locations if you have summer SAD.

Don't brush off those yearly feelings as simply a seasonal funk that you have to tough out on your own. Seek medical care if your symptoms are severe or get in the way of enjoying life.2-4,8

A Word from Thorne

Wintertime is an especially important time to consider your vitamin D levels, particularly if you live in a northern latitude. Find out what your vitamin D levels are with this simple, at-home Thorne Vitamin D Test. If you are looking for a vitamin D supplement, Thorne has several to choose from.


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  7. Galima S, Vogel S, Kowalski A. Seasonal affective disorder: Common questions and answers. Am Fam Physician 2020;102(11):668-672.
  8. Haller H, Anheyer D, Cramer H, Dobos G. Complementary therapies for clinical depression: An overview of systematic reviews. BMJ Open 2019;9(8):e028527.
  1. Seasonal affective disorder and complementary health approaches: What the science says. National Center for Complementary and Integrative Health. [Accessed Jan. 2, 2022]
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