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.
As with other kinds of depression, a person with SAD may notice any or all of these:
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.
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.
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.
If a person is diagnosed with SAD, the doctor may recommend one or more of these treatments:
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 (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.
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.
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:
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