Not everyone dreads the winter (hello ice skaters and ski bums!). But life naturally slows down during the colder months. The days get shorter, the light becomes scarce, and many of us respond by avoiding the elements. We park ourselves in front of the TV or snuggle under the covers to stay warm—the human version of hibernating. Some people embrace the season’s quiet, coziness, and snow days. But if you avoid being out in the elements and feel yourself becoming more grumpy or irritable when it’s sunnier on the other side of the planet, you may wonder if it’s more than just a passing seasonal slump. More pointedly, you may be wondering: Do I have Seasonal Affective Disorder?

What Exactly is Seasonal Affective Disorder (SAD)?

Seasonal affective disorder (SAD) is a category of depression that emerges during particular seasons of the year. Most people notice SAD symptoms starting in November and increasing during the winter months through March (the cold weather months in the northern hemisphere). Though a spring/summer version of the disorder exists as well (known as reverse SAD).

If you notice changes in your sleep patterns, energy level/productivity, and a persistent sour mood,  you may have seasonal affective disorder. To be officially diagnosed with SAD, you must experience at least two years of depression with a seasonal pattern or bouts of depression that begin during a specific time of year and fully improve during other times of the year.1

What Are the Most Common Symptoms of SAD?

Because SAD is a subset of major or clinical depression rather than a unique mental health disorder, any symptom of depression is also a symptom of SAD.2

However, certain symptoms are particularly common in people with wintertime SAD, including:

  • Fatigue
  • Low energy
  • Oversleeping
  • Increased appetite
  • Craving carbohydrates
  • Weight gain2

The less common form of SAD that occurs in the summer(reverse SAD) may be more likely to cause symptoms such as:

  • Low appetite
  • Weight loss
  • Insomnia
  • Agitation
  • Restlessness
  • Anxiety
  • Episodes of violent behavior2

Each subtype of SAD (the more common “wintertime” and the rarer “summertime” reverse type) often comes with somewhat unusual depressive symptoms, according to Raymond Lam, MD, professor and chair of depression research at the University of British Columbia.

“We know from many studies that some of the more atypical symptoms of depression are overrepresented in people with winter depression,” Dr. Lam says. “Instead of insomnia, those with winter depression may be sleeping too much. Instead of low appetite, they have a bigger appetite and experience carbohydrate cravings. Instead of weight loss, they gain weight. They also have more prominent features of energy fatigue than people with other types of depression.”

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Dean MacKinnon, MD, associate professor of psychiatry and behavioral sciences at Johns Hopkins University, likened the common symptoms of wintertime SAD—such as sleepiness and high appetite—to a kind of hibernation. “People in northern climates with shorter days tend to want to shut down. It might have been adaptive at one time to gorge during the wintertime and find food,” Dr. MacKinnon explains.

Other common symptoms with both standard major depression and SAD include:

  • Depressed mood
  • Feelings of hopelessness
  • Depleted energy levels
  • Difficulty concentrating
  • Changes in sleep and appetite
  • A loss of pleasure in activities
  • Thoughts of death or suicide

Does SAD Differ From Other Forms of Depression?

Simply put, it is a type of recurring major depression with a seasonal pattern. People with SAD experience depressive episodes during a particular season, most often in the winter months.

If you have SAD, your symptoms will likely subside when the seasons change, and the sun makes a comeback. If you notice this switch occurring annually, you may qualify for a SAD diagnosis.2  Symptoms can differ in severity, of course. The winter blues is a less severe form of SAD (see explanation “Is It SAD or The Winter Blues?” below).

If you have SAD, it may be because your body has trouble regulating the neurotransmitter serotonin, a neurotransmitter believed to responsible for balancing mood (lower serotonin levels have been linked to depression in some studies). Vitamin D, which is produced by the sun (and found in some foods), helps activate serotonin.  Less exposure to sunlight in the winter months, the thinking goes, means less vitamin D production.

Another possible issue may be an overproduction issue. Darkness (both indoors and out) signals the body to produce melatonin, the hormone that makes us sleepy. The more melatonin the body makes the more sleep and low-energy you become.

Bipolar disorder, formerly known as manic depression, is another form of depression that comes with a mix of highs (mania) and lows. Symptoms in both  major depressive disorder and bipolar disorder can have seasonal triggers which may explain why up to 20% of people who are clinically depressed and around 20% of people with bipolar disorder also have SAD.3

SAD frequently co-occurs with other disorders including attention-deficit hyperactivity disorder (ADHD), alcoholism/addiction, and eating disorders, and may be significantly underdiagnosed as a result. Treatments for each condition can be different, so it’s important to get accurately diagnosed.

SAD Risk Factors: Most At-Risk Groups 

  • Women. SAD is diagnosed four times more often in women than in men.
  • Those who live farthest from the equator. SAD is more common in areas far north or south of the equator.
  • People with a family history of SAD or other types of depression. 
  • People with depression and bipolar disorder. 
  • Younger adults.2

SAD most typically occurs in younger adult women (though some children and teens develop it, too). Women who do shift work, like nurses or other healthcare workers, are at increased risk of SAD since they make up for lost hours of sleep in the daytime when the sun is shining. Craving carbs, oversleeping frequently, and becoming severely fatigued in the winter months are common complaints.4

SAD Risk Factors: Most At-Risk Groups

SAD Risk Factors: Most At-Risk Groups

What Causes Seasonal Affective Disorder?

Like other types of depression, SAD is a complex condition that is likely caused by numerous factors—like your environment and genetics. What exactly occurs in the body to trigger SAD is not completely spelled out yet, but the general theory is that seasonal changes can disrupt the body’s biological clock, affecting its regulation of sleep, mood, and hormones.2, 7

Proximity to the equator plays a major role in SAD because people who live farther from the equator experience a greater change in the amount of daylight between the summer and the winter (summer days are long, while winter days are short). The difference in daylight hours from the summer to the winter can throw your biological clock out of whack.2, 7

The body’s biological clock tells us when to wake up and when to go to sleep. It also plays a role in regulating various chemicals and hormones that affect sleep, mood, and much more.8

The normal functioning of our biological clocks relies, in part, on light—when it is light outside, the body is supposed to be awake, and when it gets dark, it’s time to sleep. The reduction of daylight hours in the winter can confuse this pattern.8

The disruption of the body’s biological clock can trigger a chain of adverse reactions in the body that may play a role in causing SAD, including:

  • An imbalance of key brain chemicals such as serotonin. All types of depression are thought to be related to shifts in how the brain produces and uses serotonin, a neurotransmitter that helps control your mood. That’s why many common antidepressant medications work by increasing the amount of serotonin available for the brain to use. Seasonal changes may trigger serotonin imbalances in people with SAD.2
  • A change in the body’s melatonin production. The body produces melatonin, a hormone that regulates sleep, in response to darkness. The secretion of melatonin from the pineal gland usually gets suppressed by light exposure. Reduced daylight hours in the winter may lead to symptoms like fatigue and oversleeping associated with the change in melatonin.2
  • Not getting enough vitamin D. Direct exposure to sunlight prompts our body to manufacture vitamin D. Humans receive most of the necessary vitamin D via the sun. In the winter, when the days are shorter, vitamin D levels may decrease. Those with SAD may be more likely to have insufficient levels of vitamin D. Some research has also associated lower levels of vitamin D with possible depressed mood and energy but larger trials are needed to confirm that vitamin D can be used as an antidepressant.2

People who are averse to the winter’s chilly air and cloudy, windy days should know that research shows that SAD does not seem to be linked to temperature, snowfall, or cloud cover.9

Seasonal Depression Or The Winter Blues? When Should I Call The Doctor?

When it is freezing outside, and the daylight hours are fleeting, many of us head to the couch. Why not stay inside, curl up under a blanket, and watch Netflix all day?

After the 10th episode, laziness and lethargy may set in. What’s worse maybe you’ve been oversleeping and eating a little more than usual. All of this inactivity contributes to feeling low. So, how do you know if it is SAD or something milder?

That’s why seasonal affective disorder lies on a continuum, from mild to severe. There are many more people who experience the “winter blues” than those with an official SAD diagnosis.7

Mild cases, which don’t fit the clinical criteria for a SAD diagnosis, are still likely to benefit from treatment since untreated depression, in all of its many forms, puts you at greater risk of developing full-blown depression.10

One other wintertime-related cause of anxiety and stress that can trigger depression, but is not the same thing as SAD, is the holiday season and/or the post-holiday funk that follows it.

Whether your symptoms are mild or more severe, schedule an appointment with your primary care physician or mental health professional. Check to see if your workplace has an Employee Assistance Program that offers free counseling or referrals to providers in your community.

To get the best level of care, sit down, and engage your brain before your appointment. Play detective, and take some notes about the frequency and nature of your symptoms, other mental and physical health concerns you have, and observations about what helps your depression or makes it worse. Do you feel better when you spend the day outside or when you take a vacation to a more Southern location in the winter?

Jot down specific questions for your doctor and add these to your list:

  • What might also be causing my symptoms instead of SAD?
  • What treatments have your patients found helpful in the past?
  • Would you recommend a mental health provider in the community?
  • Are there any behavioral changes I can make today to help my mood?
  • Are there any written resources you’d recommend?

When you’re at the doctor’s office, he or she may conduct a physical exam or lab tests to rule out other physical causes for your depression. The doctor may also recommend that you visit a mental health professional for a more thorough assessment.

SAD Treatment Options

As with any mental health problem, there is no one-size-fits-all treatment.

People often jump to self-diagnose SAD, according to Dr. MacKinnon, but this is not recommended. SAD is a serious condition, and seeking medical advice may help prevent future episodes.9

Your doctor may recommend one of the following therapies or a combination:

Light Therapy 

Light therapy involves daily exposure to a bright, artificial light via a special box or lamp.

For a specified duration of time—usually, in the morning—someone undergoing light therapy for winter SAD will sit in front of the device every day from the early fall until symptoms subside in the spring.2, 7, 10

While you can’t have your eyes closed during this treatment, light therapy does not require you to look directly into the light, so you can sit, read, drink your morning beverage, or eat your breakfast while benefiting from the treatment.7

The process mimics the effects of sunlight, helping to reset the body’s biological clock and stabilize the imbalance of neurotransmitters and hormones such as serotonin and melatonin. 2, 7, 10

Because decreased exposure to light in the winter is thought to be the primary cause of SAD, light therapy is often the first line of treatment for winter SAD. Research indicates that it is can be an effective treatment for SAD on its own or in combination with other therapies, according to a large review of multiple studies.2, 7, 10

You don’t need a prescription to get a light therapy device, but you definitely shouldn’t go online and purchase one without consulting a doctor. While lightboxes are generally safe for most people, they are not regulated like prescription drugs are.10

Make sure that the lightbox you use filters out all or most harmful UV rays and is specifically designed to treat SAD.11

Lightboxes need to emit more light than the average lamp you have inside your home to have an effect. Brighter devices will require you to spend less time in front of them.10, 11

Your doctor will tell you the duration and intensity of light that is right for you.

In general, lightboxes should:

  • Emit between 2,000 and 10,000 lux of light
  • Give off minimal UV light 10, 11

Your doctor may recommend that you use a lightbox:

  • Early in the morning
  • For a duration of 30 minutes to two hours (depending on the intensity of the light)
  • At a distance of around two to three feet from the face
  • With eyes open but not looking directly at the light 10, 11

While light therapy is generally safe and well-tolerated, it’s not totally benign or without risks.2, 7, 10, 11

Light therapy may not be safe for use on people with past or current eye problems, such as glaucoma, cataracts, or diabetes-related eye damage, as it can potentially cause further damage to the eyes.7, 11

It can also trigger manic symptoms, so people with bipolar disorder should not undergo light therapy without a doctor’s approval and close monitoring.7, 11

Light therapy can also cause side effects, including headache, eyestrain, nausea, and agitation. Changing the intensity or duration of light exposure or the distance between you and the device may relieve these side effects.7, 11

Medication for SAD

When light therapy fails or is not sufficient on its own at alleviating your symptoms, your doctor may recommend medication.

Like other types of depression, SAD can be treated with a class of prescription medications called antidepressants.

Antidepressants are primarily effective at preventing SAD in people who have predictable, annual bouts of depression. Those with recurring winter depression, for example, may begin taking antidepressants in the early fall, before symptoms arise.12

When the fall becomes winter and people with SAD are apt to fall into depression, antidepressants are thought to work by maintaining adequate levels of various neurotransmitters in the brain, like serotonin.12

To date, only one antidepressant is specifically approved for the prevention of SAD—bupropion (extended-release)—but many other antidepressants may work, too.2, 11

A type of antidepressant drug called a selective serotonin reuptake inhibitor (SSRI) is also commonly prescribed for SAD. As the name suggests, these drugs work by affecting the brain’s production of serotonin.2, 12

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Medication requires patience, though, and it can take several weeks before you begin to feel the effects. It’s also important not to stop taking the drug if you feel better. Consult with your doctor before you change your dosage, and let him or her know if you experience any side effects.

Vitamin D Supplements

In the winter, when the days are shorter and people aren’t getting outside as much, it makes sense that people might become deficient in vitamin D, a vitamin that the body produces in response to sunlight.2, 13

Research has shown that all people are vulnerable to vitamin D deficiency in the winter, especially those with SAD.2

Vitamin D supplements may help SAD, but not enough research has been done to support this theory. The research that does exist is mixed.2

Although vitamin D supplements are not proven to treat or prevent SAD, talk to your doctor to see if they may be helpful for you.2


Psychotherapy (aka talk therapy) can be an invaluable option for treating, managing and reducing SAD symptoms and reoccurrence.

Many different therapy types may be helpful, but one in particular, called cognitive-behavioral therapy (CBT), has been highlighted as a particularly useful treatment option for SAD.2, 6

Regardless of what type of therapy you choose, the idea is that working with a psychotherapist can help you identify the negative thoughts and patterns that contribute to your depression and learn ways of breaking the cycle.2, 7

What Can I Do Today to Ease Seasonal Affective Disorder?

The condition that has become known as SAD was first described by a physician who experienced it himself. When Norman Rosenthal, MD, moved to the United States from his native South Africa to work at the National Institutes of Health (NIH) 40 years ago, he was struck by the difference he felt during the winter months. South Africa is warm and sunny year-round—a climate comparable to southern California—so the difference was easy for him to see. He made note of the most noticeable changes in his mood and energy level and how they both improved in the springtime.1

Later he collaborated with researchers who were studying the relationship between light, melatonin, and circadian rhythms. That work led, in 1984, to the development of the Seasonal Pattern Assessment Questionnaire (SPAQ), a free, self-assessment tool that continues to be used today.

Use it to gauge your own experience but be sure to seek help from your doctor who can advise you about treatment options including lifestyle changes that can improve symptoms and lift your mood.

In the meantime, try going outside more often, getting plenty of sunlight during daytime hours, exercising, avoiding drugs and alcohol, getting plenty of sleep, and practicing relaxation exercises.6

An integrative psychiatrist—someone who emphasizes combining established treatments like medication with complementary measures like lifestyle changes, meditation, and exercise—can provide more advice on how to manage SAD beyond the conventional treatments. You could also do what the Danes do. In Scandinavian countries, where the sun only shines for 4 or 5 hours a day during the darkest time of the year, hygge helps people get through it. Pronounced hyoo-guh, hygge is a Danish word that loosely translates to “coziness” or “comfort” and is a practice of being content at home with simple pleasures like spending time with the family playing board games in front of a crackling fire. It’s described as the happy feeling you’d get snuggling indoors on a cold day.

“With something like seasonal depression, there are so many things one can do in addition to, or beside, medications,” says Gregory Scott Brown, MD, a board-certified psychiatrist and affiliate faculty member at the University of Texas Dell Medical School in Austin, Texas. “There’s a growing body of evidence supporting the benefit of vitamin D. We know that spending more time outside—getting more sunlight—is a totally appropriate treatment option to consider.”

Planning a healthier lifestyle is never a bad idea, but don’t beat yourself up if your symptoms don’t improve right away. Don’t brush them off as the January blues and simply hunker down until spring. Asking for help is a sign of strength and movement toward a better version of yourself. Consider how you can start managing seasonal affective disorder today and live a healthier life in every season.


How is SAD treated?

The four main treatments for SAD are light therapy, antidepressants, psychotherapy, and vitamin D supplementation. These may be used alone or in combination. A psychologist can help direct you to the right treatment plan for you.

What causes SAD?

The exact cause of SAD has yet to be defined, and it is likely due to a combination of genetic, biological, environmental, and psychological factors. Research indicates that seasonal changes, specifically the reduction of sunlight in the winter, may offset the body's biological clock, triggering changes in mood, sleep, and hormone production in people with SAD. Other factors that may play a role in causing SAD include an imbalance of crucial brain chemicals such as serotonin, an overproduction of melatonin, and a vitamin D deficiency.

Where is SAD most common?

SAD is more common in places that are far north or south of the equator. For example, only an estimated 1% of Floridians experience SAD, compared with 9% of those who live in Alaska.

How can I help someone with SAD?

If you know someone is suffering from SAD, you can help by gently encouraging them to seek medical advice for their treatment. If they're already being treated, help them adhere to their prescriptions or appointments. Be patient, supportive, and encouraging, and focus on listening rather than dispelling advice. If you're worried they're at risk for suicide, you can dial the National Suicide Prevention Lifeline at 1-800-273-TALK (8255). You can also text their Crisis Text Line by texting “HELLO” to 741741.

By the Numbers: 

The prevalence of SAD among the general population ranges from around 1.5% to up to 9%. The higher end of that estimate is concentrated in places far from the equator, where the seasons change more dramatically. For example, only an estimated 1% of Floridians experience SAD, compared with 9% of those who live in Alaska, according to one study.6

Winter SAD is much more common than its summer variation. Half a million Americans are estimated to experience winter SAD, and millions more experience milder forms of the winter blues.6

Helpful Resources

National Institute of Mental Health (NIMH)

NIMH is the lead federal agency for research on mental disorders. You’ll find the latest research, news, and statistics on SAD here.

National Alliance on Mental Illness (NAMI)

NAMI is the nation’s largest grassroots mental health organization. It is made up of more than 600 local affiliates and 48 state organizations to help provide information and support for different mental health conditions. For free information and support, you can call the NAMI HelpLine at 1-800-950-NAMI (6264) or email In a crisis, you can text “NAMI” to 741741.

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Last Updated: May 18, 2021