Seasonal Affective Disorder (SAD)

"Claire" began her sophomore year in high school eager to make new friends and committed to doing well in her classes. Then, as winter approached and the days grew shorter, Claire noticed that she needed more sleep than usual. Even after sleeping more, she had no energy and felt fatigued, moody, and depressed.

When she tried to write articles for the school paper, something that normally came easy for her, Claire had trouble concentrating. She started to miss deadlines. When it came time to print the newspaper, Claire had no articles to turn in. Over the next two months, friends stopped calling her. When Claire complained that no one invited her to sit with them at football games or attend weekend sleepovers, her parents became concerned.

Over the winter break, Claire had an appointment with her doctor. Claire told her doctor how tired she felt. She said no matter how much she slept, it was never enough to end her fatigue and sad mood. She also mentioned that she had gained weight since August, and that her appetite for carbs, especially chips and cookies, had greatly increased.

After doing a physical exam, Claire’s doctor ruled out other problems that cause fatigue and mood changes and diagnosed Claire with seasonal affective disorder, or SAD.

What Causes Seasonal Affective Disorder?

Seasonal affective disorder, also referred to as winter or seasonal depression, is a syndrome with depression that starts and ends at the same time each year.

There are two types of SAD: fall-onset SAD and summer-onset SAD. The fall-onset type, often called "winter depression," is more recognized. With less sunlight during these two seasons, some people who are predisposed to depression may be more likely to develop an episode. While the neurobiological causes of SAD are not well-established, it is thought that brain areas which regulate mood and operate using the neurotransmitter serotonin may not function properly. The National Institutes of Health estimates that more than 36 million Americans suffer seasonal depression that occurs in the fall.

Hormones manufactured in the brain that are affected by sunlight exposure may play a role in the development of SAD and its symptoms of depressed mood, fatigue, carbohydrate cravings, and weight gain. Because foods high in carbohydrates (like chips, pretzels, and cookies) boost serotonin, it is thought that they have a soothing effect on the body and mind.

SAD usually starts in young adulthood. It is more common in females than in males. Some teens with SAD have very mild symptoms and just feel out-of-sorts or irritable. Others have more serious symptoms that interfere with relationships and schoolwork.

Because the lack of daylight during wintertime is related to SAD, it is seldom found in countries within 30 degrees of the equator, where the sun shines year round.


Symptoms of SAD

If you have SAD that begins in the fall, like Claire’s, you might have the following symptoms:

  • Increased need for sleep
  • Increased appetite with carbohydrate craving
  • Weight gain
  • Irritability
  • Inability to concentrate
  • Problems with relationships (being sensitive to rejection)
  • A heavy feeling in arms or legs
  • The times you've been depressed during the fall/winter season outnumbering the times you've been depressed at other times over your lifetime

When SAD begins in the spring or summer months, teens might have symptoms of depression such as weight loss, decreased need for sleep, and poor appetite.

What Are the Treatments for SAD?

There are different treatments for SAD, depending on the severity of the symptoms. If you have another type of depression or bipolar disorder, the treatment may be different.

Many doctors recommend that patients with SAD try to get outside early in the morning to increase their exposure to natural light. If this is impossible during dark winter months, antidepressant medications and/or light therapy (phototherapy) may be used. Light therapy involves a full-spectrum light that is shined directly into your eyes.

How Does Light Therapy Work for SAD?

With light therapy for SAD, you sit about 2 feet from a bright light (about 20 times brighter than normal room lighting). You start with one 10-minute to 15-minute session per day. The time is then increased to 30 minutes-45 minutes a day, depending on your response. Some teens recover within days using light therapy; others take much longer.

If the SAD symptoms don't stop, your doctor may increase the light therapy sessions to twice daily. Those who respond to light therapy are encouraged to continue until they can be out in the sunshine again in springtime. Light therapy alone may not be enough to relieve SAD. Since SAD is a form of major depression, an antidepressant may be helpful.

Some researchers link SAD to the natural hormone melatonin, which causes drowsiness. Because light modifies the amount of melatonin in the human nervous system and boosts serotonin to the brain, light therapy has an antidepressant effect. When light strikes the eye's retina, a process in the body decreases the secretion of melatonin.


When Should I Call My Doctor About SAD?

If you have feelings of depression, fatigue, and irritability that come at the same time each year, you may have a form of SAD. Talk openly with your doctor about your feelings. Follow the doctor’s recommendations for lifestyle changes and/or treatment if you have SAD.

If your health care provider recommends light therapy, ask if they provide light boxes for patients with SAD. You can also rent or purchase a light box, but they are expensive and health insurance companies do not usually cover them. While side effects are minimal with light therapy, be cautious if you have sensitive skin or have a tendency toward mania (feeling elated, excited, and unable to sleep).

WebMD Medical Reference Reviewed by Smitha Bhandari, MD on February 24, 2016



Kessler, R. Archives of General Psychiatry, 1994. 

Wehr, T. American Journal of Psychiatry, 1987. 

Miller, A. Altern Med Review, March 2005. 

Rosenthal, N. Primary Psychiatry, Sept.-Oct. 1994. 

Coiro V. Psychoneuroendocrinology 1993. 

Sep-Kowalikowa B. Psychiatria Polska, Nov.-Dec. 2002. 

Diagnostic and Statistical Manual of Mental Disorders, 4th ed., American Psychiatric Association, Washington, 2000. 

Rosenthal, NE, Oren, DA, "Light Therapy" In: Treatment of Psychiatric Disorders, 2nd ed., Gabbard, GO (Ed), American Psychiatric Press, Inc., Washington, 1995. 


© 2016 WebMD, LLC. All rights reserved.