CBT May Trump Light Therapy for SAD in the Long Run

Liam Davenport

November 17, 2015

Cognitive-behavioral therapy (CBT) appears to achieve better long-term outcomes than light therapy for seasonal affective disorder (SAD), with greater remission rates and less severe symptoms, say US researchers.

Investigators at the University of Vermont, in Burlington, found that following 6 weeks of CBT for SAD (CBT-SAD) or light therapy, CBT patients were almost twice as likely to be in remission and were more likely to stay in remission than those who received light therapy.

"CBT-SAD should be considered as an efficacious SAD treatment and disseminated into practice, particularly if the focus is on recurrence prevention," the investigators, led by Kelly J. Rohan, PhD, write.

"The thinking around this is that CBT teaches skills. It teaches people things that they can do in terms of changing their thinking styles and their behavioral responses in times of stress or at times when their mood is shifting towards sadness," Dr Rohan told Medscape Medical News.

"It creates a kind of toolbox approach, in that the person has skills that they can draw from in the future to try to fortify themselves against having relapse or a recurrence, and this is not the case for a treatment such as light therapy that is a more passive application of a medical device to suppress symptoms," she added.

The study was published online November 5 in the American Journal of Psychiatry.

Long-term Focus

The team randomly assigned 177 adults who had major depression that was recurrent with a seasonal pattern to 6 weeks of CBT-SAD or light therapy and followed them for two winters.

Follow-up visits took place in January and February of each year, and the patients were assessed by telephone in October and December of the first year. Major depression status was assessed using the Structured Interview Guide for the Hamilton Depression Rating Scale–Seasonal Affective Disorder Version, which includes the Hamilton Depression Rating Scale and the Beck Depression Inventory–Second Edition (BDI-II).

There were no significant differences between CBT-SAD and light therapy on any of the outcomes at the first winter follow-up. There was also no significant difference in SAD recurrence at the October and December calls, at 12.3% for CBT-SAD and 21.1% with light therapy (P = .154).

During the second winter, however, CBT-SAD was associated with a significant reduction in SAD recurrences vs light therapy, at 27.3% vs 45.6%, as well as less severe symptoms, as indicated on both questionnaires.

Patients undergoing CBT-SAD were also more likely to be in remission, defined as a BDI-II score ≤8, than those given light therapy, at 68.3% vs 44.5%. Interestingly, those patients receiving CBT-SAD whose symptoms did not recur in the first winter were more likely not to experience symptom recurrence in the second winter than their counterparts receiving light therapy (relative risk, 5.12 and 1.92, respectively).

Dr Rohan said that the emergence of differences between outcomes with CBT and light therapy during the second winter is at odds with the results of her previous pilot studies, in which differences were seen in the first winter.

"I was a little puzzled by this initially, but then I considered the methodological differences between my prior studies and this bigger, better study," she said.

"What we did over the first year of follow-up may have been overly invasive, in that we were tracking people really closely. We saw them the summer after they finished treatment, and then we called them twice in the fall, once in September and December, and we physically saw them in January or February.

"So I fear that in our very intensive follow-up procedures, we might have created what is known as a 'testing effect,' where people might have changed their behavior on the basis of the research itself.... We might have been prompting people to do things that they would not have otherwise done."

Dr Rohan pointed out that the long-lasting effect of CBT is not, in itself, a new finding.

"It's a new finding in CBT for SAD, but this is pretty much the story across CBT treatments. With CBT for depression, for example, people who receive the treatment have fewer relapses and recurrences of their depression than individuals initially treated with antidepressant medications," she said.

One outstanding question is whether the combination of CBT and light therapy would yield greater benefits than either would alone. Interestingly, Dr Rohan tested this in a previous study, finding that, over the longer term, patients who received both therapies did better than those who received only light therapy, but they did less well than those given CBT alone.

In the current study, the researchers investigated the two treatments separately.

"My perspective is very long-term focused, in that this is recurrent depression that comes back year after year. So we have to take a long-term perspective in terms of trying to keep people well over time, not trying to get the most dynamite treatment response that we can get across 6 weeks in the winter.

"That's why, in doing this larger study, I went to a two-cell approach, just comparing CBT to light. In the future, I'd certainly like to explore the combination further.

"Very possibly, there are people out there who would benefit more from a combination treatment, not just in the short term but perhaps in the long term as well. That's probably a subgroup of patients, and I need to do a lot more work to try to figure out who those people are, for whom that additional cost...would pay off in the form of benefits," she said.

Apples and Oranges?

Commenting on the study for Medscape Medical News, Michael Terman, PhD, president of the Center for Environmental Therapeutics and professor, Department of Psychiatry, Columbia University, in New York City, questioned the validity of comparing the two therapies, saying the study attempted to compare "apples and oranges."

"A problem here is the radical difference in the nature of the two interventions. The logic underlying the two modalities — physiological and cognitive — is not parallel, and their comparison provides no basis to claim superiority of one over the other," said Dr Terman.

"The authors fault light therapy for the burden of daily sessions and the expense of apparatus, though 6 weeks of CBT would cost far more. They suggested purchasing light boxes after year 1 of free treatment, a disincentive that would contribute to lower adherence.

"The light therapy dropout rate by year 3 made reliance on inferential intent-to-treat analysis and logistic regression critical for ferreting out the signal, leading to a weaker conclusion than with nearly complete data sets. What if the informed consent had included an agreement to continue treatment in years 2 and 3 under monitoring, with study-supplied light boxes?"

Dr Terman pointed out that light therapy is a long-standing treatment and has had a major impact on patients' lives.

"Thirty years after the introduction of light therapy for SAD, there are patients that have successfully and routinely avoided winter depression with brief exposure to bright light upon awakening. In itself, light therapy abates their fear of winter — a main goal of CBT for SAD," he said.

"Light therapy was designed as a maintenance treatment, in analogy to medications. Beyond its antidepressant action, it is a direct energizer and circadian rhythm–entraining agent. Withdrawal of light therapy during the winter season leads to relapse within 3 weeks. Without such relapse, one suspects a placebo response.

"By comparison, CBT for SAD is a teaching exercise designed to confront relapse by means of cognitive restructuring to curtail the subjective adversity of successive winters. One would expect a residual benefit of CBT for SAD in the years following without treatment — the authors' hoped-for, and now achieved, result."

Summarizing, Dr Terman said that "to conclude that CBT for SAD is greater long-term benefit than light therapy, when assiduous attention was not paid to continuation treatment with light therapy and creation of a support system to encourage adherence, is unfortunate.

"Light therapy patients may be wont to 'test the system' by seeing if they can get by without treatment. The same, of course, is true for psychoactive medication. Here is an area where psychoeducation would serve a constructive end. Call it CBT for treatment adherence and compare that with CBT for SAD...."

The study was supported by a grant from the National Institute of Mental Health, the Mental Illness Research Education and Clinical Center, and VISN 19 Rocky Mountain MIRECC, Denver. Dr Rohan receives book royalties from the Oxford University Press for a treatment manual for the cognitive-behavioral therapy for SAD intervention. No other authors have disclosed any relevant financial relationships.

Am J Psychiatry. Published online November 5, 2015. Abstract

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