Bright Light Therapy May Have Potential to Treat Bipolar Depression

For those with seasonal affective disorder, or SAD, bright light therapy has been used as a method of treating the condition. After observing the positive results from the therapy, researchers at Northwestern University conducted a recent study to determine whether the therapy would also be beneficial to those with bipolar disorder.

The study’s 46 participants were adults with depression who also had bipolar disorder, and who were already taking antimanic medication. The participants were randomly assigned to sit in front of either a 7,000-lux bright white light or a 50-lux dim placebo light, referred to as a box.

“We usually ask people to sit in front of the box at a distance of 12 to 13 inches away and to position the light at eye level,” said Dorothy Sit, a psychiatrist and the study’s lead researcher, in an interview with NPR. “They can certainly read; read the paper; journal; look at their bills.”

The researchers’ goals were to figure out a remission rate, depression symptom level, a rate of mood polarity switch and to explore the participants’ sleep quality. Symptoms were measured on a weekly basis with a depression scale, known as the Structured Interview Guide for the Hamilton Depression Scale With Atypical Depression Supplement (SIGH-ADS), the Mania Rating Scale, and the Pittsburgh Sleep Quality Index.

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“Sixty-eight percent of of the patients improved with bright light therapy versus only 22 percent of patients on the placebo box,” Sit said. “Patients returned to work; they were able to look after things at home; they were functioning back to their normal selves again.”

A remission was defined by the researchers as having a SIGH-ADS score of eight or less. Both the bright light therapy and placebo groups had moderate depression, with no hypomanic or manic symptoms.

No mood polarity switches were observed, and the patients’ sleep quality improved for both groups but did not differ between the two. Al Lewy, a psychiatrist and professor at Oregon Health and Science University, known as a pioneer of bright light therapy, said the study is interesting, but there’s more to know for those who suffer from bipolar disorder.

“If you do the light, particularly in the morning, with bipolar depression, you might cause the person to switch into a manic episode,” Lewy said.

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He added that patients should consult their doctor before attempting the therapy. The study permitted light therapy in the middle of the day. After four to six weeks, the participants saw lower depression scores.

The study authors wrote that the data provides strong evidence that supports the efficacy of midday bright light therapy for bipolar depression. Ken Duckworth, the medical director of the National Alliance on Mental Illness, said new treatments for bipolar depression are a need, since it’s one of the most difficult types of depression to treat.

“People with bipolar disorder spend most of their time on the depressive end of the spectrum, and this difficulty is compounded by the fact that we don’t have very good treatments for the depressive phase of bipolar disorder,” Duckworth said.