‘Tis the season of darkness. The clocks are turned back, the biological clock on those pretty leaves outside is a-tickin’, and soon it will be nothing but bare branches and 4:45 p.m. sunsets. This is a certifiable bummer for all of us in the Northern Hemisphere, but for people who suffer from Seasonal Affective Disorder, it's worse: As the sun goes, so too goes their mental health.

For many with SAD, this means dragging out the light-therapy lamp. Light therapy is the most researched and widely-used treatment for SAD. It requires a person to sit under a very bright light for 30 minutes upon waking, every day that he or she would have symptoms.

But according to a new study funded by the National Institute of Mental Health and published in The American Journal of Psychiatry, cognitive behavioral therapy could be better for patients in the long run than light therapy. In the largest randomized trial to date on this, the researchers followed 177 people as they underwent light therapy or CBT tailored for SAD for six weeks, then checked back in with them during the subsequent two winters.

That first winter, CBT and light therapy worked pretty much equally well at reducing people’s depressive symptoms and putting their SAD into remission. And they were evenly matched at the first follow-up appointment, too. But by the second follow-up appointment, CBT had pulled ahead. Among the group that got CBT, 27.3 percent had their depression come back the second winter, compared to 45.6 percent of those who got light therapy, and symptoms were less severe for the people in the CBT group as well. Even after the researchers controlled for any other treatments the patients might have tried in the meantime, the difference between the CBT group and the light-therapy group remained.

Kelly Rohan, a professor of psychology at the University of Vermont and the lead author of the study, suspects that one reason for this may be that while CBT teaches people a set of skills they can use forever, you have to spend time with the light box every day for it to work.

“[CBT] is not a treatment that you have to be in every day for five months of the year indefinitely,” she says. “A light box isn’t really a treatment that gives you a sense of agency or control over your symptoms.”

Cognitive behavioral therapy has already been shown to have long-term benefits for nonseasonal depression, and Rohan sees her results as part of that pattern. Though SAD is a condition that comes from the environment, it might be more helpful to patients to focus their treatment on the “depression” part rather than the “seasonal.”

“You can’t control what time the sun rises and the sun sets,” Rohan says. “I mean, I guess you could by moving dramatically to a new latitude, but assuming there are good reasons to stay in the area where you live, then I think this is good news. You can manipulate the light in your environment by using light therapy, and that is an effective treatment. However there’s another way, by changing your thinking style and your behavior, that might actually confer longer term benefits than light therapy.”