“Cognitive behavioral therapy is a form of talk therapy that seeks to change thought patterns and behavior,” Dr. Rohan said. She explained that C.B.T. and light therapy “could not be more different.”

“In one, you’re sitting in front of a box to jump-start your circadian rhythms,” she explained. “In C.B.T., a person’s thoughts and behaviors provide an entry point.” In other words, C.B.T. is active and light therapy is palliative. Dr. Rohan’s study found that over time, the behavioral skills C.B.T. instills reduced the recurrence of SAD in a greater proportion of patients than those who used light therapy alone.

Dr. Michael Young, past president of the the Society for Light Treatment and Biological Rhythms, said it makes sense that changing one’s behaviors would affect SAD symptoms. While he called Dr. Rohan’s findings “a little disappointing for those of us in the light field,” he also touted the long-term benefits of C.B.T.

“On the psychological side, part of [C.B.T.] teaches people skills to help themselves,” he said. “Once people learn those, they don’t tend to forget them. It doesn’t require putting aside half an hour [to sit in front of a light lamp] or continuous meds, which only work if you take them.” He also emphasized the importance of finding a C.B.T.-trained practitioner who has experience treating SAD specifically, since more focused treatment is more effective, over all.

Exercise and small behavioral changes can keep depression at bay

All of the experts agreed that, especially when combined with either light therapy or C.B.T., small behavioral changes can make a big difference. Dr. Young recommended heading outside and getting some exercise, especially in the morning.

“People’s behaviors can affect biology and psychology,” he said. “For all sorts of depression, [sufferers] decrease activity, decrease social interactions and decrease activities that give us pleasure because we think we won’t enjoy things. It’s a biological phenomenon: Physical activity is good for our mood.” Even on cloudy days, he noted, the amount of sunlight outside still has a better effect than artificial light indoors.

So-called natural antidepressants like getting out of the house and staying active can have a great effect on SAD symptoms, Dr. Rohan noted. “I don’t necessarily push people to do winter activities, but find your own way to engage [with the season],” she advised. “We’re trying to change the hands and trying to change the head, but the hands can change the head.”