What to Know About Seasonal Depression

Medically Reviewed by Jabeen Begum, MD on April 30, 2024
Written by Debra Fulghum Bruce, PhD
8 min read

Seasonal depression, also known as seasonal affective disorder (SAD), is a mood disorder that happens every year at about the same time. It usually starts in fall or winter and ends in spring or early summer. These mood changes may affect how you feel, think, and act.

SAD may affect 11 million people in the U.S. each year, and 25 million more may have a milder form called the winter blues.

Seasonal depression in summer

A rare form of seasonal depression, known as "summer depression," begins in late spring or early summer and ends in fall.

While we don't know the exact causes of SAD, some scientists think that certain hormones made deep in your brain trigger attitude-related changes at certain times of the year.

One theory is that less sunlight during fall and winter leads your brain to make less serotonin, a chemical linked to brain pathways that help control mood. When these nerve cell pathways don't work the way they should, it can result in feelings of depression, along with fatigue and weight gain.

SAD usually starts in young adulthood and is more common in women (and those identified as female at birth). Some people with SAD have mild symptoms, feeling out of sorts or cranky. Others have symptoms serious enough to interfere with relationships and work.

Because SAD that starts in winter is related to the reduced levels of daylight, it's less often found in countries where there's plenty of sunshine year-round.

It's not clear what causes SAD that starts in spring or summer. Some believe it's linked to higher levels of light that may disrupt sleep patterns. It also may be linked to increased social pressures, as more events are scheduled during warm weather.

People with SAD typically sleep much more than usual and crave carbohydrates. They also have many of the normal warning signs of depression, including:

  • Feeling sad or down most of the time
  • Less energy
  • Trouble concentrating
  • Fatigue
  • Increased appetite
  • More desire to be alone
  • Thoughts of suicide
  • Loss of interest in things you used to enjoy
  • Sleeping too much
  • Overeating and weight gain 
  • Feelings of guilt or worthlessness

Winter seasonal depression

If you have SAD in fall and winter, you may:

  • Experience fatigue or lack of energy
  • Oversleep
  • Notice changes in appetite
  • Crave for starchy foods
  • Stay home more and avoid socializing

Summer seasonal depression

If you have SAD in spring and summer, you might have:

The main feature of SAD is that your mood and behavior shift along with the calendar. It's not a separate mood disorder but a type of major depression or bipolar disorder, sometimes called manic depression.

You may have SAD if, for the past 2 years:

  • You had depression or mania that started as well as ended during a specific season
  • You didn't feel these symptoms during your "normal" seasons
  • Over your lifetime, you've had more seasons with depression or mania than without 

Sometimes, it might take a while to diagnose SAD because it can mimic other conditions, such as chronic fatigue syndrome, underactive thyroid, low blood sugar, viral illnesses, or other mood disorders.

If your doctor thinks you may have SAD, they may:

  • Give you a physical exam to see if you have health problems that may be causing your symptoms
  • Do blood tests to help rule out physical illnesses
  • Ask you about your thoughts, feelings, and behavior
  • Ask you to fill out a questionnaire about your symptoms

Treatments differ, depending on how serious your seasonal affective disorder symptoms are. The type of treatment you get also depends on whether you have another type of depression or bipolar disorder.

Seasonal depression medication

Traditional antidepressants are often used to treat SAD. Bupropion XL is FDA-approved specifically to prevent major depressive episodes in people with SAD. But your doctor may suggest other medications.

You may start taking an antidepressant each year before the time your seasonal depression usually sets in. That's because these medications take some time to start working.

Seasonal affective disorder therapy

Cognitive behavior therapy can help teach you ways to better manage your symptoms and deal with negative thoughts and behaviors. It can also help you learn self-care strategies.

Vitamin D for seasonal depression

Low levels of vitamin D have been found in people with SAD. It may be caused either by getting too little of the vitamin in your diet or not getting enough sunshine. But it's unclear whether vitamin D supplements can help ease SAD symptoms. Very little research has been done on dietary supplements other than vitamin D for SAD.

One of the most effective ways to treat SAD that starts in fall or winter is with light. Some researchers link seasonal depression to the natural hormone melatonin, which causes drowsiness. Light affects our brain's biological clock, which regulates the circadian rhythm — a physiological process that can lead to mood changes in winter when there’s less sunlight. Natural or "full-spectrum" light can have an antidepressant effect.

Light therapy

In this therapy, a full-spectrum bright light shines indirectly into your eyes. You sit about 2 feet away from a bright light — about 20 times brighter than normal room lighting. The therapy usually starts with one 10- to 15-minute session per day. Then, the times increase to 30-45 minutes a day, depending on your response.

Some people with SAD recover within days of using light therapy. Others take much longer. If the SAD symptoms don't go away, your doctor may increase the light therapy sessions to twice daily. People who respond to light therapy are encouraged to continue it until the springtime when they can be out in the sunshine again.

Seasonal depression lamp

You can buy light therapy lamps over the counter, but talk to your doctor first about whether this treatment is right for you and the best way to use it. Look for a lamp that emits at least 10,000 lux of light with as few damaging UV rays as possible.

Side effects of light therapy

While the side effects of light therapy are minimal, be cautious if you have sensitive skin, eye problems, or a history of bipolar disorder. Overusing light therapy could bring on symptoms of mania for those with bipolar, so let your doctor know if you have this condition.

Also, tell your doctor if you have a history of eye disorders such as cataracts, glaucoma, or damage resulting from diabetes. Never look directly at the light source for a long time, to avoid any damage to your eyes.

Outdoor activity

Many doctors recommend that people with SAD get outside early in the morning to get more natural light. If this is impossible because of the dark winter months, antidepressant medications or light therapy (phototherapy) may help.

There's been little research on how to prevent SAD. But these tactics may help:

  • Spend some time outside every day, even when it's cloudy. The effects of daylight still help. If it’s too cold out, open your blinds and sit by a sunny window.
  • Begin using a 10,000-lux light box when fall starts, even before you feel the effects of winter SAD.
  • If your doctor has prescribed antidepressant medication, ask them about the best time to start taking it.
  • Eat a well-balanced diet that includes plenty of fruits and veggies, whole grains, and lean proteins. This will help you have more energy, even if you're craving starchy and sweet foods.
  • Exercise regularly. Aim for at least 30 minutes a day, five times a week.
  • Stay involved with your social circle and regular activities. Social support is very important.

Exposing yourself to light, eating right and exercising, and staying socially involved will help you feel better. Other steps you can take include:

  • Don't wait to get professional help. If you have symptoms that go beyond "winter blues," see your doctor or a mental health professional.
  • Keep an eye on your sleep patterns. Try to go to bed and wake up at about the same time each day. If you take naps, make them short.
  • Think about light in your environment. Open the blinds at your workplace, and trim foliage that blocks sunlight to your windows at home.
  • Schedule time to do things you enjoy, whether that's seeing the latest hit movie or doing volunteer work.
  • Avoid alcohol and recreational drugs. They'll only make you feel worse in the long run.
  • Don't put too much pressure on yourself while you're feeling depressed. Set priorities for what's most important, and tackle your to-do list one item at a time.
  • It may be best to avoid major life decisions during your "down" season.
  • Have a friend or family member to confide in. Don't be afraid to reach out to them for help when you need it.
  • Understand that it may take some time for your symptoms to lift.

If you start feeling depressed, fatigued, and cranky around the same time each year, you may have a form of SAD. Talk openly with your doctor about your feelings. Follow their recommendations for lifestyle changes and treatment.

If your doctor recommends light therapy, ask if the practice provides light boxes for patients with SAD. You can also rent or purchase a light box or lamp, but health insurance doesn't usually cover them.

Seasonal depression is a mood disorder that you get each year at about the same time. It most often occurs in fall or winter, but can also start in spring or summer. Tell your doctor if you notice seasonal mood changes. SAD can be treated with light therapy, talk therapy, medication, and lifestyle changes.

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What are the seasonal features of depression?

Seasonal features of depression are the patterns of symptoms that affect people with SAD at specific times of the year. Those with SAD that starts in winter tend to have tiredness, sadness, and lack of motivation. SAD that starts in spring or summer may bring insomnia and irritability.

What is the difference between seasonal depression and depression?

The main difference is that seasonal affective disorder symptoms predictably flare up at certain times of the year — usually fall and winter — and ease when the season changes. Depression can happen anytime, and it's hard to predict how long its symptoms will last.

Is seasonal depression a form of bipolar?

Seasonal affective disorder is considered a type of major depressive disorder and a form of bipolar disorder. Those with SAD have symptoms of either major depression or bipolar only during certain times of the year. People with SAD are more likely to have major depressive disorder than bipolar disorder. Those with bipolar and SAD often have depressive episodes in fall and winter and mania during spring and summer.

How do different seasons affect your mood?

It's common to feel less energetic, positive, and social from time to time when it's cold outside and there's less daylight. But with seasonal affective disorder, these feelings are more intense and last all season long.

What is the best way to deal with SAD?

The best treatment depends on how serious your symptoms are and whether you have another type of depression or bipolar disorder. One of the best-known and most effective ways to treat wintertime SAD is light therapy. In this therapy, you spend time each day in front of a box or lamp that emits very bright light. Medication, psychotherapy, and lifestyle changes can also help treat seasonal depression.

When does SAD start?

Most people with SAD start having symptoms in late fall or early winter. They usually ease as warmer weather arrives in late spring and summer. Some people, though, have SAD symptoms in spring and summer.