Darker days have arrived across the Northern Hemisphere and, for many people, so has seasonal depression. For years patients have turned to light therapy, regular exposure to artificial light that's meant to mimic the longer days of milder seasons.
But now a multi-year study suggests that specialized talk therapy sessions may actually have longer-lasting benefits than light exposure for treating seasonal affective disorder, or SAD.
Cognitive-behavioral therapy (CBT) is a type of talk therapy that's been used to fight other types of depression for decades. Sessions involve working with a professional therapist to learn methods of thinking, speaking and acting that eliminate negative thoughts and replace isolating behaviors with more positive activities to banish the blues.
Quite a bit of scientific literature indicates that over the long run, psychotherapies and particularly CBT can produce a better outcome than other treatments for depression. But CBT has only recently been applied to SAD, so its benefits in this realm were unclear.
The National Institute of Mental Health funded a large-scale study to explore CBT and light therapy effectiveness over time. One hundred seventy-seven SAD patients were randomly assigned treatment with either six weeks of light therapy or six weeks of CBT therapy.
In the CBT sessions, therapists introduced cognitive skills to identify and challenge negative thoughts associated with SAD, like the expectation that the upcoming winter means loneliness and gloom. Behavioral skills then helped patients find fun activities, schedule them and actually do them to counteract the seasonal “hibernation” that can fuel depression.
Led by Kelly Rohan of the University of Vermont, the study at first found that improvement was comparable during an initial six-week treatment period, whether patients used a light box for half an hour upon waking each day or attended a 90-minute group CBT session twice a week.
The following September, participants were encouraged to either resume light therapy or use the skills they learned in CBT on their own. The team conducted in-person follow-ups during that winter and, again, no difference was apparent in the effectiveness of the two treatments.
But during another follow-up two winters later, nearly half of the light therapy subjects reported recurring depression, while only 27 percent of the CBT group did. The light therapy group also suffered worse depressive symptoms than those who'd used CBT.
It turns out that only 30 percent of the study participants were still using light therapy by the second winter follow-up, the team reports in the American Journal of Psychiatry. The study authors think the difference might be due to the burden of upkeep—over enough time, patients have to work harder to maintain their light therapy schedules than they do keeping up with their CBT skills.
Psychological and behavioral factors produce long-term benefits in all kinds of other medical conditions as well, notes Michael Young of Illinois Institute of Technology, who is also past president of the Society for Light Treatment and Biological Rhythms.
“So in that sense, this study is not so strange in the context of depression treatment studies in general,” he says. “If you think about heart disease, everybody knows you need to take your medicine, eat better and get some exercise. But what makes most of the difference in outcomes is not getting that prescription. It's helping people do the right things. And that has to do with how they think about it and the behavioral strategies they use."
According to Young, both treatment options likely address the biological basis for SAD, just in different ways. Drops in sunlight can alter the brain's balance of serotonin and melatonin, chemicals that help govern sleep patterns and mood. Replacing some of that lost light with special lamps can fool the brain into restoring normal rhythms.
While CBT is unlikely to have this exact type of impact on the brain, changing people's behavior can affect their physical systems, too.
“Even our genes don't operate in a vacuum. There's often an interaction of genes and behavior or environment," Young says. "So the idea that getting people up and doing more things, and increasing positive experiences that you tend to avoid when depressed by staying in and feeling helpless and hopeless, those things have effects on biology as well as psychology.”
Treating any kind of depression, though, is about figuring out what works best for each patient, he says. Some people may benefit more from CBT or from light therapy, and others may prefer a mix of these and other treatments.
“They can all produce the same kinds of beneficial outcomes,” he notes. “And that's what we really care about with our patients.”