A study published online today in the American Journal of Psychiatry casts a shadow on light therapy’s status as the gold standard for treating seasonal affective disorder (SAD).
While the treatment is effective at addressing acute episodes of SAD, a SAD-tailored version of cognitive behavioral therapy (CBT) is significantly better at preventing relapse in future winters, the study found. Led by University of Vermont psychology professor Kelly Rohan and funded with a $2 million grant from the National Institute of Mental Health, it examined light therapy’s effectiveness over time.
In the study, 177 research subjects were treated with six weeks of either light therapy—timed, daily exposure to bright artificial light of specific wavelengths using a light box—or a special form of CBT that taught them to challenge negative thoughts about dark winter months and resist behaviors, like social isolation, that affect mood.
Two winters after the initial treatment, 46% of subjects in the light therapy group reported a recurrence of depression compared with 27% of those in the CBT group. Depressive symptoms were also more severe for those in the light therapy group.
“Light therapy is a palliative treatment, like blood pressure medication, that requires you to keep using the treatment for it to be effective,” Rohan says in a release. “Adhering to the light therapy prescription upon waking for 30 minutes to an hour every day for up to five months in dark states can be burdensome.”
The study showed that, by the second winter, only 30% of light therapy subjects were still using the equipment.
Cognitive-behavior therapy, by contrast, is a preventive treatment, Rohan says. Once SAD sufferers learn its basic skills it has enduring impact, giving the person a sense of control over their symptoms.
A companion study Rohan published in the American Journal of Psychiatry in September showed that light therapy and CBT were both highly effective in treating SAD during the winter they were administered, with no statistically significant differences between the two approaches.
“The degree of improvement was substantial,” Rohan says. “Both treatments showed large, clinically significant improvements in depressive symptoms over six weeks in the winter.”
But given the difficulty in persisting with light therapy and large number of Americans suffering from the recurrent disorder, CBT may be the better treatment option in the long term, she says.
For the study, research subjects were started at 30 minutes of light therapy each morning at home, and the duration was subsequently adjusted to maximize response and reduce side effects over 6 weeks. Light therapy subjects were instructed to continue daily exposure at home until spring and were offered access to a light box again the next winter. A second group of subjects received cognitive-behavioral therapy during two 50-minute sessions per week for 6 weeks.
In the first winter after the initial treatment. the two treatment groups reported comparable relief from seasonal depression.
Photo: A new study by Kelly Rohan, professor of psychological sciences, shows that cognitive behavioral therapy is more effective at preventing relapses than light therapy. Photography by Andy Duback