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Seasonal Affective Disorder (SAD)

Also called: SAD, Seasonal Depression

What Is Seasonal Affective Disorder?

Seasonal affective disorder (SAD) is depression that happens 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.

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?

The exact cause of SAD isn't clear, but some teens' brains react differently to fewer hours of daylight.

Daylight affects two chemicals in the brain:  serotonin and melatonin . When it’s sunny, the brain makes more serotonin. High levels boost feelings of happiness and well-being. Low levels lead to depression. When it’s dark, the brain also makes more melatonin. High levels cause you to feel sleepy and have less energy.

Shorter days and more hours of darkness in fall and winter may decrease serotonin and increase melatonin. This makes depression more likely to happen.

How Is SAD Diagnosed?

If you think you might have SAD, talk with your parents or doctor. To diagnose it, your doctor will ask you questions and listen. You’ll likely need a health checkup to see if the symptoms are due to SAD or something else.

How Is SAD Treated?

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

More Light Exposure

Spending more time outside during daylight hours may be enough to ease SAD. Take a daily walk or do another exercise outdoors. You can also bring more daylight into your home 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 45 minutes a day.

SAD may improve within a few days or weeks. Like any medical treatment, only use light therapy after checking with your doctor.

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. The treatment can also help you understand SAD and learn how to prevent it.


Doctors may prescribe medicine like an antidepressant, which can help balance chemicals in the brain.

How Can I Feel Better?

If you're diagnosed with SAD, follow your doctor's advice for treatment and be patient. It can also help to:

  • Get plenty of exercise, especially outdoors. Both daylight and physical activity can lift your mood.
  • Spend time with friends and loved ones.
  • Ask your teachers for help with homework if you need it. 
  • Drink water and try to eat plenty of whole grains (like oatmeal and brown rice), vegetables, and fruits. Avoid less healthy foods and drinks like candy and soda. When your body feels better, your brain will feel better.
  • Go to bed and get up at the same time each day. This can help you get enough sleep and daytime light.

What Else Should I Know?

SAD and other forms of depression are serious. If you think you have symptoms of any type of depression, talk with a trusted adult, like a parent, teacher, or school counselor. 

If there isn’t an adult to turn to, reach out to a confidential helpline. These are free and available 24 hours a day:

Reviewed by: Lisa M. Buckloh, PhD
Date Reviewed: Oct 1, 2023

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