Bright Light Therapy Improves Bipolar Depression

Pauline Anderson

October 09, 2017

Midday bright white light therapy may be effective for patients with bipolar depression, new research suggests.

In a new study, this treatment approach resulted in a better antidepressant response compared to exposure to dim red light in patients with bipolar disorder.

"We clearly saw differences in effect between the bright light vs the placebo between weeks 4 and 6," lead author Dorothy K. Sit, MD, associate professor, Department of Psychiatry and Behavioral Sciences, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, told Medscape Medical News.

Moreover, the therapy did not result in hypomania, which was an adverse event "we were worried about. So in that respect, it's pretty safe," said Dr Sit.

The treatment, which is portable and easy to use, "offers another option" to drug therapy for bipolar patients, she added.

The study was published online October 3 in the American Journal of Psychiatry.

The analysis included 46 patients (mean age, 44.7 years; 67% women) with confirmed bipolar disorder, moderate major depression (mean score of 26 on the Structured Interview Guide for the Hamilton Depression Rating Scale With Atypical Depression Supplement [SIGH-ADS]), and no hypomania or psychosis. Study participants were receiving stable doses of antimania medication. Most patients were enrolled in the study during fall or winter months.

Patients were randomly assigned to a group that received broad- spectrum bright white fluorescent light (7000 lux) or to one that received inactive dim red light (50 lux).

The active treatment was similar to that used for seasonal affective disorder (SAD), although for SAD, a 10,000-lux light box is typically used, said Dr Sit.

The researchers ensured that patients treated with antidepressants were equally distributed between the two groups.

Despite randomization, baseline depression and global functioning scores differed significantly between groups. However, because both groups had moderate levels of depression and impaired function and there were no other demographic or clinical differences, the authors judged the two groups to be comparable.

The active and placebo light boxes looked identical when not illuminated. Evaluators and participants were blinded, and patients were asked not to research light therapy.

The patients were instructed on the optimal use of the light box ― placing it 12 inches away and facing the box without directly looking at it.

The patients began with daily 15-minute light therapy sessions that took place between noon and 2:30 PM, and they attended weekly assessment visits. After each visit, they length of the light sessions was increased by 15 minutes, for a target dose of 60 min/d by week 4 or until remission.

This dose-titration approach is similar to that used in trials of medical therapy, noted Dr Sit.

Higher Remission Rates

The current study, in which light therapy was administered at midday, differed from a previous study by Dr Sit and team, in which therapy was administered in the morning. The concern was that administering the therapy during morning hours may elicit circadian resetting. Bipolar patients are sensitive to circadian dysregulation; in that pilot study, some patients developed bipolar cycling or hypomania.

Primary outcomes in this new study were the rate of remission, defined as a SIGH-ADS score of 8 or less, within 4 to 6 weeks and the continuous SIGH-ADS scores at the endpoint visit.

For the active treatment group, the remission rate at weeks 4 to 6 was significantly higher than for the inactive group (68.2% vs 22.2%; odds ratio [OR], 7.50; 95% confidence interval [CI], 1.80 - 31.28; P = .003). The OR was 12.64 (95% CI, 2.16 - 74.08; P = .004) after adjusting for age, season at enrollment, and baseline Global Assessment of Functioning (GAF) Scale and SIGH-ADS scores.

"What we found was pretty much on par with what we see for drug studies," said Dr Sit.

Remission rates in the active treatment group began to increase dramatically at about 4 weeks. "Patients were still continuing to get better at 6 weeks," said Dr Sit.

It is possible that the patients may have continued to improve with more treatments. Dr Sit noted that in the future, they may extend the treatment to 8 weeks. "But there's a concern that the longer we conduct the trial, the higher the risk for dropouts. And we may not want to have patients exposed to an inactive comparator for 8 weeks."

The investigators also found that at the endpoint visit, mean depression score was lower in the treated group than in the inactive group (mean SIGH-ADS score, 9.18 vs 14.94; adjusted P = .023).

For patients in the active treatment group, global functioning, as reflected in GAF score, was significantly better than for patients in the inactive treatment group. For the patients who received active treatment, response rate was higher (proportion with reductions of at last 50% on the SIGH-ADS), and there was less anxiety, fewer social problems, and better sleep quality, but these differences were not significant.

No Hypomania

There was no hypomania or mood polarity switch. The novel light-dose titration approach might have prevented the emergence of hypomania or mania, the authors note.

It is not clear, said Dr Sit, why morning light exposure would result in hypomania, whereas exposure to midday light does not seem to.

Five patients in the inactive group dropped out, and one patient in the active group dropped out, owing to the fact that she was not allowed to use the light box at work. The early withdrawal rate was not significantly different between the groups, and the expectations of treatment also "weren't that different," said Dr Sit.

"So patients were likely not dropping out because they were expecting less of a positive effect; it was more related to the fact that they weren't getting any better."

The researchers did not investigate the impact of SAD because, they said, subanalyses would be underpowered and would provide inconclusive results.

Many in the study enjoyed the experience, because it allowed them to relax, read, and work on puzzles or on their computer during light exposure sessions, said Dr Sit.

Light therapy is "an appealing option for folks who are not experiencing a good enough response" to drug therapy or who experience troubling side effects from such therapy, she said.

Although treatments for bipolar mania "are quite good," those for bipolar depression "are still not satisfactory," she added.

Dr Sit recommended that clinicians monitor bipolar patients who undergo light therapy and that patients choose a light box similar to that used in the study. She noted that light boxes need to be large enough to provide adequate illumination.

She also stressed that patients should not expect to experience results before at least 4 weeks. "Short duration of treatment may not be sufficient."

Encouraging Signal

Commenting on the study for Medscape Medical News, Stephen M. Strakowski, MD, chair, Department of Psychiatry, Dell Medical School, University of Texas, Austin, said the study is "important and timely," that it is "a great initial step," and that "the signal is encouraging."

But it does not answer all the questions concerning the use of light therapy for patients with bipolar depression, said Dr Strakowski.

"We don't know what the best dose really is, and we don't really know when the best time of day to give it is," because the study did not directly compare morning vs midday light exposure.

Dr Strakowski also questioned whether the blinding of patients to the treatment was effective, because they could have gone on the Internet to find relevant information on light therapy.

He thought it would have been "interesting" had the patients been asked which group they thought they were in. However, he acknowledged the difficulty of fully blinding such a study.

"Some would say that if it's working, we don't care."

Dr Sit and Dr Strakowski have disclosed no relevant financial relationships.

Am J Psychiatry. Published online October 3, 2017. Abstract

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