Bright light therapy at midday: Does it help in bipolar depression?

Bright light therapy done at midday may be an effective and affordable adjunct to antimanic medication in patients with bipolar depression (BD), according to an expert who presented at APA 2021. This brings renewed attention to this natural, somatic treatment primarily used for seasonal depression.

“We, light therapy experts and clinicians in the field, would like to advocate that patients initiate and continue light therapy under the guidance of medical experts,” said study author Dr Dorothy Sit, associate professor, department of psychiatry and behavioural sciences, Northwestern University’s Feinberg School of Medicine, Chicago, Illinois, US. “Exposure to white light may enhance remission rates in our patients.”

Red light no better

Forty-six individuals with depression and bipolar I or II disorders on the background of antimanic medication were included in the trial. Twenty-three of them were randomly assigned to 7,000 lux bright white light and 23 to 50 lux dim red placebo light at midday.

Weekly assessments via 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 were conducted to assess remission rate and depression symptom level, rate of mood polarity switch, as well as sleep quality. Remission was defined as a SIGH-ADS score of eight or less.

After 4-6 weeks of treatment, patients who were exposed to bright white light therapy demonstrated a significantly higher remission rate of 68.2 percent vs 22.2 percent for those on placebo.

At the final clinic visit, those on white light therapy also had a significantly lower depression score of 9.2  vs 14.9 for the placebo comparator. Additionally, there were no mood polarity switches observed. Improvement in sleep quality was not significantly different between groups.

For circadian rhythms and moods

Bright light therapy is gaining a lot of traction in the mental health community as a novel treatment for BD. It is used initially to treat seasonal affective disorder (SAD) or seasonal depression. Current clinical indication for bright light therapy also includes advanced or delayed sleep/wake phase disorders.

“Light therapy is typically implemented to reset and amplify circadian rhythms that have been disrupted,” said Sit. “It also improves mood symptoms even in cases where disruption in circadian rhythms is not the primary cause.”

Bright light therapy may also be used to improve alertness levels, uplift mood, and restore functioning and social engagement, thus reversing the symptoms of depression and anxiety, she added.

How and when to start treatment

It is recommended to set up the lightbox at 7,000 lux broad-spectrum white light. “That produces a cooler 4,000 Kelvin bluish light … it is good to start at 15 minutes per day between noon and 2:30 pm,” said Sit. The distance of the lightbox from the user should be between 12–14 inches. It should be within eye level and tilted downward.

Additional exposure of 15 minutes each week is advised to reach a target of 45–60 minutes. When used daily, it can improve seasonal affective symptoms within 2–4 weeks. The onset of efficacy is quick, usually within 3 to 4 days, said Sit.

“Maintenance therapy is essential, with the antimanic therapy crucial to help patients avoid the risk of inducing mania or mixed symptoms,” she concluded.