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Seasonal Affective Disorder

What Is Seasonal Affective Disorder?

Seasonal affective disorder (SAD) is depression that happens to a person only at a specific time of year. With SAD, a person becomes depressed in fall or winter, when days are shorter and it gets dark earlier. SAD is brought on by the brain’s response to the seasonal changes in daylight. When the daylight hours grow longer again, the depression lifts.

SAD is also called seasonal depression. 

What Are the Signs & Symptoms of SAD?

As with other kinds of depression, a person with SAD may notice any or all of these:

  • Changes in mood. SAD can cause a mood that’s sad, depressed, or irritable. SAD can make people feel hopeless, discouraged, or worthless. They may cry or get upset more easily.
  • Negative thinking. A person can become more self-critical, or more sensitive to criticism. They may complain, blame, find fault, or see problems more often than usual.
  • Lack of enjoyment. People with SAD may lose interest in things they normally like to do. They may lose interest in friends and stop participating in social activities.
  • Low energy. People may feel tired, low on energy, or lack motivation to do things. To them, everything can seem like it takes too much effort.
  • Changes in sleep. A person may sleep much more than usual. They may find it especially hard to get up and ready for school or work in early morning hours.
  • Changes in eating. SAD may bring on cravings for simple carbohydrates (think comfort foods and sugary foods) and the tendency to overeat. Because of this change in eating, SAD can result in weight gain during the winter months.
  • Trouble concentrating. Like any depression, SAD can make it hard to focus. This can affect schoolwork and grades.

With SAD, a person notices these changes only during the time of year when there are fewer hours of daylight. As the season changes and days become longer again, their depression gets better and their usual energy returns.

What Causes SAD?

Seasonal depression is brought on by the brain’s response to shorter daylight hours. Daylight affects two chemicals in the brain, melatonin and serotonin. These chemicals help regulate a person's sleep–wake cycles, energy, and mood.

Melatonin is linked to sleep. The brain makes more melatonin when it's dark. Higher melatonin levels cause a person to feel sleepy and less energetic. Serotonin is linked to mood and energy. The brain makes more serotonin when a person is exposed to sunlight. Higher levels of serotonin boost feelings of happiness and well-being. Low levels of serotonin lead to depression.

Shorter days and longer hours of darkness in fall and winter may cause higher levels of melatonin and lower levels of serotonin. This creates the biological conditions for depression.

How Is SAD Diagnosed?

Health care providers are trained to diagnose SAD after a careful evaluation. This includes asking questions and listening. A health checkup can make sure that symptoms aren't due to another condition.

How Is SAD Treated?

If a person is diagnosed with SAD, the doctor may recommend one or more of these treatments:

More Light Exposure

For many people with SAD, simply spending more time outside during daylight hours is enough to relieve seasonal depression. Exercising outdoors or taking a daily walk are ways to do this. People can also bring more daylight into their homes during winter months by using special daylight light bulbs that fit in regular lamps.

Light Therapy

Light therapy (also called phototherapy) uses a special light box that is placed on a tabletop or desk. The person sits in front of the light for a short period of time every day (45 minutes a day or so, usually in the morning).

With daily light therapy, seasonal depression improves within a few days for many people. It can take up to a few weeks for others. Even after they feel better, people who use a light therapy box for SAD continue to use it until enough sunlight is available outdoors.

Like any medical treatment, light therapy should be used only after talking about it with a doctor. The person should carefully follow the instructions that come with the light box.

Talk Therapy

Talking with a therapist helps relieve the negative thoughts and feelings associated with depression. It can ease the isolation or loneliness that people with depression often feel. It can help people understand their condition, and learn what to do to prevent future bouts of seasonal depression.


Doctors may prescribe medicine for some people with SAD. Antidepressant medicines help balance serotonin and other neurotransmitters that affect mood and energy.

How Can I Feel Better?

If you think you might have SAD, talk to your parent or doctor about what you’ve been feeling.

If you're diagnosed with SAD, there are things you can do to help yourself:

  • Follow your doctor's advice for treatment.
  • Get plenty of exercise, especially outdoors. Both daylight and exercise are mood lifters.
  • Spend time with friends and loved ones who understand what you're going through — they can help you feel connected and cared about.
  • Be patient. Don't expect your symptoms to go away right away.
  • Ask for help with homework and other assignments if you need it. Talk to your teachers to work out a plan to get your assignments done. If you feel you can't concentrate on things, remember that it's part of SAD. Remind yourself that things will get better again.
  • Eat right. It may be hard, but avoid simple carbohydrates and sugary snacks. Eat plenty of whole grains, vegetables, and fruits to help you feel better.
  • Develop a sleep routine. Regular bedtimes and wake times can help you gain the mental health benefits of sleep and daytime light.

Depression in any form can be serious. If you think you have symptoms of any type of depression, talk to someone who can help you get treatment.

Reviewed by: D'Arcy Lyness, PhD
Date Reviewed: Jan 10, 2020

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