From Medical Correspondent Dr. Steve Salvatore

NEW YORK (CNN) -- The upcoming holiday season is supposed to be full of cheer. But for many, the winter season brings on the blues. Doctors say light treatment may offer a cure -- naturally.

Researchers from Columbia University say the controversial therapy can offer relief for a severe form of the winter blues known as seasonal affective disorder, or SAD.

Their study is one of three on light therapy reported in the current issue of Archives of General Psychiatry.

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"What we're doing is stretching the winter day into a springtime day or a summertime day," said Michael Terman, director of the winter depression program at the Columbia-Presbyterian Medical Center. "That tricks the brain into thinking it's in the alternate season."

Light therapy brings outdoor levels of light into your home for 30 minutes a day with a powerful box light.

Terman studied 124 patients and found improvement in 60 percent of those who received light treatment in the morning. He found 30 percent had improved after being treated with light in the evening.

"For a generation now, we've relied on antidepressant medication to make people feel better and here we find a very naturalistic intervention that does the same job or perhaps even better for some people." Terman said.

Light therapy has been used for more than a decade, but its effectiveness has been debated.

Some health experts have felt previous studies failed to offer the scientific proof that light therapy works. And most insurance companies don't consider it an acceptable treatment.

"If the medical community has not taken light therapy seriously, this is the time for them to really pay attention and recognize it as a highly effective treatment that could benefit millions of people," said Dr. Norman Rosenthal, a senior researcher at the National Institutes of Health and the author of "Winter Blues," a book on the topic.

Seasonal affective disorder, which affects about 10 million Americans, begins in late fall or early winter. It can cause fatigue, create a craving for carbohydrates, hinder sleep, and bring on depression.

The Associated Press contributed to this report.