Probing Question: What is Seasonal Affective Disorder?

Chris Tachibana
January 12, 2010

You know those occasional mornings when you want to pull the covers over your head and avoid the world? If those off-kilter moods seem to happen more in the winter months, it might be time to consider whether Seasonal Affective Disorder, or SAD, is responsible for your blues, says Frederick Brown, associate professor of psychology and director of the Human Performance Rhythms Laboratory.

"A diagnostic feature of SAD is that it is a depression that reoccurs at the same time every year beginning in the fall and early winter," explains Brown " with remission in the late winter and early spring. SAD sufferers have a hard time getting out of bed, they have carbohydrate cravings, and they tend to put on weight in the fall and early winter, when they feel down and may even feel sick."

woman reading in front of a light therapy box and woman wearing a light visor to treat seasonal affective disorder
Parker Home Health Care and

Light therapy box and light visor used to treat Seasonal Affective Disorder.

Brown is a specialist in chronobiology, a field that studies the effect of daily, monthly and seasonal cycles on our behavior and performance. "Many of us experience changes in the fall and early winter months that are not necessarily SAD," he notes. "Like any animal, we respond to shorter day lengths by preparing for winter. We have a tendency to put on weight, especially after Thanksgiving, and we may experience a reluctance to get up in the morning." For people with SAD, however, these seasonal changes can become serious and disrupt their work and affect their mood, clarifies Brown.

Best estimates are that upwards of 10 percent of Americans may be affected by SAD, he adds. It often begins in the 30-something years, and women are overwhelmingly more likely to have it than men. SAD may be more common in certain geographic areas. "In general," says Brown, "the most northern and southern areas of the world during fall and winter are the most affected by depression." Since SAD seems to be caused by lack of light, it's less common in areas of the world where sandy deserts and snow create light-reflecting glare.

"The eyes are not just for seeing," Brown explains. "We physiologically respond to the daily light they collect for adjusting our waking and sleeping times." Light inhibits production of the sleep-promoting hormone melatonin, and darkness causes melatonin to be released from the pineal gland in the brain. As the night comes sooner in the fall and winter, this happens earlier.

"Some people are more sensitive to these changes," says Brown. "It's assumed to have a genetic component." People with SAD may have a harder time getting a good, deep sleep. This might lead to difficulty waking up, daytime sleepiness, changes in mood, and depression.

"An additional 10 percent of people may suffer sub-clinically, with milder "winter blues" symptoms," according to Brown, who suggests three sensible, easy steps to making winter tolerable.

"Turn on a lot of lights in the morning," says Brown. "Aim for the amount of light at 8:00 a.m. on a sunny June day." He's found many homes are not well lighted, with less than 1/20th the amount of light that is available outdoors. He also advises, "Skip the sugary donuts and danish and eat a high protein breakfast, which puts us in gear for the day." Another recommendation: "Go outside for 20 or 30 minutes in the middle of the day. Get exposure to natural light." Brown says full-spectrum light therapy boxes are recommended by medical specialists along with prescribed medication in severe cases of SAD, but just greatly increasing daily light exposure in general may be as just as effective. Finally, Brown has good news for SAD sufferers. "Daylight is becoming longer now, so your symptoms should get better."

Frederick M. Brown, Ph.D., is associate professor of psychology in the College of the Liberal Arts and director of the Human Performance Rhythms Laboratory at Penn State. He can be reached at

Last Updated January 12, 2010