It's a sad season, indeed, that sees hundreds of thousands of Americans hibernating at home, huddled on the couch with high-calorie snacks in hand.

It's a sad season, indeed, that sees hundreds of thousands of Americans hibernating at home, huddled on the couch with high-calorie snacks in hand.

Not surprisingly, January and February are the most difficult months for sufferers of Seasonal-Affective Disorder (SAD), or winter depression, a condition experienced by 10 to 20 percent of people nationwide, according to the American Academy of Family Physicians. Short of moving south for the winter, patients can wait out SAD's cycle — recently linked to circadian rhythms and melatonin levels — or try a few relatively simple and straightforward strategies that stave off symptoms.

"Every fall and winter, we get a lot of calls," says Dr. Alfred Lewy, a professor of psychiatry at Oregon Health & Sciences University in Portland. "Oregon is kind of a mecca for seasonal-affective disorder."

Despite Oregon's reputation for perpetual rain and cloud-cover, SAD sufferers can blame the state's geographic location. Days become shorter the farther north one travels in winter. More specifically, a later sunrise has been tied to SAD, but the absence of light isn't the condition's sole cause.

"Not everybody gets depressed because the days are shorter, so there's got to be some underlying biological component," Lewy says.

Scientists at the University of Virginia recently linked the prevalence of SAD to mutation

of a gene that produces light-sensitive protein found in the eye's retina and thought to play a role in circadian rhythms, hormones, alertness and sleep. Researchers concluded that someone with two copies of the mutated melanopsin gene was five times more likely to develop SAD, compared with someone without the mutation, according to a November article by the Connecticut-based news service HealthDay.

The findings coincided with statistical evidence that SAD runs in families. The condition also is known to affect more women than men, with onset in the young adult or teenage years rather than in old age.

Moving to Oregon from Oklahoma in her 20s, Sherrie Baxter felt the first stirrings of SAD, which also dogged her mother.

"I was a little night-owl in the winter," Baxter says. "I just wasn't myself at all."

Baxter's mother in the late 1980s signed up for OHSU's first study of light-box therapy for SAD patients. When she mentioned her daughter's malaise, Baxter also was welcomed into the three-week regimen that controlled participants' light exposure.

"It made a huge difference for me," Baxter says. "I kind of became a light-therapy missionary."

In her mission to manufacture light boxes for herself and her mother from high-intensity fluorescent tubes, Baxter had a bright business idea. Eighteen years later, her Vancouver, Wash.-based Enviro-Med is one of the country's main manufacturers of light boxes.

"It's worked for me for many years," Baxter says. "It's noninvasive — no drugs."

Up to a hundred times brighter than the light in most rooms, light boxes are the most commonly prescribed treatment for SAD. Because the tubes give off no ultraviolet rays, there's no risk of skin damage, Baxter says.

The treatment's main drawback is time. SAD sufferers should spend 20 to 30 minutes in front of the light box after they get up in the morning. By the end of the first week, users should notice their symptoms improving, Baxter says, adding that she offers a free, one-month trial on her products. Only about 7 percent of the hundreds of light boxes sold each year are returned to the company, she says.

"You're really just fooling your brain into thinking there's an early summer sunrise."

The brain also can be fooled with low dosages of melatonin administered at strategic intervals, Lewy says. The psychiatry professor in 2006 published an article in the scientific journal Proceedings of the National Academy of Sciences that cited the effectiveness of melatonin supplements in treating SAD. However, Lewy says light-box therapy will remain the preferred remedy until melatonin supplements are marketed in the lower, sustained-release dosages needed to make their prescription practical for SAD sufferers.

"It's very counterintuitive that melatonin helps anybody with winter depression because it's a dark signal."

Anyone feeling down during winter's darkest days can benefit from the same activities that counteract depression regardless of season, says Michael O'Connell, psychologist and owner of Rogue Valley Psychological Associates. Exercising, maintaining an active social circle and avoiding chemicals that affect mood can foster feelings of cheer in the SAD season.