Bright light therapy beneficial in unipolar depression with evening chronotype

Results of the world’s first randomized controlled study on adjunctive bright light therapy (BLT) for patients with unipolar major depressive disorder and concomitant evening chronotype, conducted by investigators from the Chinese University of Hong Kong (CUHK) show greater and more rapid remission of depression with BLT vs dim red light (DRL) with gradual timing advancement protocol.

“We are among the first research groups to suggest that disruption of circadian preference, particularly evening-type circadian preference, is a crucial factor determining the clinical outcome of depression,” said Professor Yun-Kwok Wing from the Department of Psychiatry, CUHK.

“Results of our former study showed that 19.4 percent of outpatients with depression were of evening chronotype. These patients had significantly increased severe depressive symptoms [p<0.01], insomnia severity [p<0.01] and suicidality [p<0.05], and a significantly decreased rate of remission [p<0.005],” said Dr Joey Chan from the Department of Psychiatry, CUHK. [Sleep 2014;37:911-917]

“Our current study showed that 5-week timed BLT vs DRL with gradual advancement in start time led to significant improvements in time to remission [p=0.024] and likelihood of remission of depression [hazard ratio, 1.9; 95 percent confidence interval, 1.1 to 3.4; p=0.026],” said Chan. “[At a follow-up of 5 months,] BLT also showed a higher cumulative remission rate vs DLT [67.4 percent vs 46.7 percent].” [Psychol Med 2020, doi: 10.1017/S0033291720003232]

“Light is an important cue in synchronizing the internal biological clock with the external environment. Timed BLT reduces circadian misalignment for patients with depression and evening chronotype. Its mechanism of action is thought to be linked to modulation of the serotonin system in the brain,” explained Dr Shirley Li from the Department of Psychiatry, CUHK.

The study included 93 patients (mean age, 46.4 years; female, 80 percent) with unipolar nonseasonal depression and concomitant evening chronotype. The patients were randomized (1:1) to receive 5 weeks of 30-minute daily therapy with a light box emitting either 10,000 lux white light (BLT group) or 50 lux red light (DRL group) at eye level at a distance of 40 cm, with the same advancement protocol in start time. The initial start time of light therapy was set within 1 hour of the patient’s habitual wake time, as determined by the prescriber based on 1 week of sleep pattern recorded on a sleep diary at baseline.

The patients’ average duration of depressive illness was 13.7 years and mean 17-item Hamilton Depression Score (17-HDS) was 19.3. The mean bedtime and rise time at baseline were 01:21 am and 10:25 am, respectively, and mean morningness-eveningness questionnaire (MEQ) score was 35.3.

BLT also demonstrated significant improvements in secondary outcomes of Hamilton Anxiety Rating Scale (p<0.001), Hospital Anxiety Depression Scale (p<0.001), Insomnia Severity Index (p=0.002), Beck Scale for Suicidal Ideation (p<0.001), Chadler Fatigue Scale (p=0.005), and 36-item Short Form Health Survey (p=0.014) vs DRL.

“There is little concern with BLT regarding treatment-related adverse events [TRAEs] and potential drug interactions. BLT may thus be a promising effective adjuvant treatment for patients with depression, particularly those who are unable to tolerate psychotropic medications,” said Chan.

“BLT can also be considered in advancing the sleep pattern in patients of evening chronotype,” said Wong. “We look forward to exploring the application of BLT and other circadian-related chronotherapeutic measures in different psychiatric disorders and patient groups.”