When snowy winters approach, Heather Gibbons tries to stay happy - but it doesn’t always work.

“When it’s really snowy, I get depressed because it seems like it’s never going to stop,” the family community services junior said. “I try to make the best of it by watching movies and hanging out with friends. I try to have as much fun as I possibly can.”

Many college students stuck on chilly campuses may be suffering from Seasonal Affective Disorder, or its milder form, “The Winter Blues.”

The disorder is a form of clinical depression that occurs most commonly in the fall and winter. It commonly occurs in the United States, Canada, Europe, Australia and Japan.

It affects between 5 and 10 percent of the U.S. population - especially to people in their teens and early 20s.

Symptoms of the disorder include low energy, constant fatigue, difficulty concentrating and an inability to enjoy normally pleasant activities such as socializing and sex.

“It’s a physiological condition that can be treated but never cured,” said Dr. Thomas Hranilovich, a psychologist at Psychiatric Associates of Ingham, 2220 University Drive in Okemos. “Someone with the disorder should always try to be outdoors during the daytime. It’s almost always brighter outdoors during the daytime than inside in a lit room.”

“The Winter Blues” may affect an additional two to three times as many people as the clinical disorder form, and can still cause significant distress and impair daily functions.

About 75 percent of people who suffer from the disorder are women, but it can affect men and children.

Some common causes of the disorder include the amount of normal daylight exposure and changes in the timing of sunrise and sunset that are characteristic of the fall and winter months.

Hranilovich said the disorder is caused by the pineal gland, located in the brain, which produces melatonin. The enzyme responds to changes in the level of light. It causes drowsiness when the lights are dimmed or turned off.

“The cells in the pineal gland are a lot like the cells in the retina,” Hranilovich said. “They are light-sensitive and control your moods if you have the disorder.”

The Psychiatric Associates of Ingham recommend light boxes to patients. The boxes generate an intensity of 2,500 to 10,000 lux of light one to two feet from the patient’s eyes. The purpose of the boxes is to enhance seratonin levels while regulating melatonin levels. Melatonin is the hormone that keeps the sleep rhythms in sync with the outside world.

Most light boxes cost between $300 and $500 and are sold through mail-order specialty manufactures.

Although bright light exposure is likely to alleviate some of the mood or energy level symptoms, the most successful disorder treatments result from identifying how a person’s daily rhythms have shifted, particularly in their sleep.

“Everyone has a circadian rhythm 24-hour clock which controls hormones and sensitivity,” said David Copenhagen, a professor of ophthalmology at the University of California, San Francisco, who has researched the way people react to additional light.

“The way you adapt to changes in your cycle is with light. The cells in your eye that detect light help reset the clock.”

Family community services junior Justin Tate said winter depression affects many things in his life.

“I listen to depressing music sometimes and pretty much my whole mind-state isn’t good,” Tate said. “It affected my grades freshman year because I didn’t go to class.

“I try to be around friends though, and do things with them. That helps me become happier.”