A meta-analysis found that bright light therapy may be an effective adjunctive treatment for nonseasonal depressive disorders. 

The study, published in JAMA Psychiatry, showed patients receiving bright light therapy (BLT) in addition to standard treatment had significantly higher remission and response rates compared to control groups.

The systematic review and meta-analysis included 11 randomized clinical trials with 858 patients. Key findings included:

• Remission rates: 40.7% for BLT group vs 23.5% for control group (odds ratio [OR], 2.42; 95% CI, 1.50-3.91; P <.001; I2 = 21%)
• Response rates: 60.4% for BLT group vs 38.6% for control group (OR, 2.34; 95% CI, 1.46-3.75; P <.001; I2 = 41%)
• Subgroup analysis showed benefits for both short-term (<4 weeks) and longer-term (>4 weeks) follow-up

The researchers conducted a comprehensive search of MEDLINE, Embase, SCOPUS, Web of Science, PsycINFO, and Cochrane databases for randomized clinical trials published between January 1, 2000, and March 25, 2024. Eligible studies compared BLT alone or as an adjunct to antidepressants against placebo, antidepressant monotherapy, or dim red light in patients with nonseasonal depressive disorders.

Of the 858 patients included, 649 (75.6%) were female and 209 (24.4%) were male. The analysis used the Mantel-Haenszel random-effects model and assessed heterogeneity using I2 statistics.

Subgroup analyses based on follow-up time revealed:

• Remission rates at <4 weeks: 27.4% (BLT) vs 9.2% (control); OR, 3.59; 95% CI, 1.45-8.88; P = .005; I2 = 0%
• Remission rates at >4 weeks: 46.6% (BLT) vs 29.1% (control); OR, 2.18; 95% CI, 1.19-4.00; P = .01; I2 = 47%
• Response rates at <4 weeks: 55.6% (BLT) vs 27.4% (control); OR, 3.65; 95% CI, 1.81-7.33; P <.001; I2 = 35%
• Response rates at >4 weeks: 63.0% (BLT) vs 44.9% (control); OR, 1.79; 95% CI, 1.01-3.17; P = .04; I2 = 32%

The study examined changes in depression rating scales:

• Hamilton Rating Scale for Depression (HAM-D): Significantly greater reduction in BLT group (mean difference [MD], -1.44; 95% CI, -2.40 to -0.48; P = .003; I2 = 0%)
• Clinical Global Impressions Scale (CGI): No significant difference (MD, -0.06; 95% CI, -0.29 to 0.16; P = .56; I2 = 0%)
• Montgomery-Åsberg Depression Rating Scale (MADRS): No significant difference (MD, 0.36; 95% CI, -2.60 to 3.31; P = .81; I2 = 23%)

Nine studies used BLT at 10 000 lux for 30 to 60 minutes daily, one study used 7000 lux, and one used 5000 lux.

The meta-analysis included studies with various types of depressive disorders:

• 7 studies focused on major depressive disorder
• 3 studies examined bipolar depressive disorder
• 1 study included both major depressive disorder and bipolar disorder

A meta-regression analysis evaluating the relationship between remission rate and age at onset of major depressive disorder (MDD) approached statistical significance (P = .06), suggesting a possible link between these variables.

The researchers noted several limitations:

• Slight differences in follow-up times between trials
• Variability in definitions of remission and response across studies
• Inability to analyze bipolar and unipolar subtypes of MDD separately due to data limitations
• Moderate number of included studies may have affected the I2 statistics

The study's quality assessment using the Cochrane Risk of Bias tool found all included randomized controlled trials to be at low risk of bias. A funnel plot analysis suggested a low probability of publication bias affecting the general results of remission and response rates.

This meta-analysis provided evidence supporting the use of BLT as an adjunctive treatment for nonseasonal depressive disorders, with potential implications for clinical practice in managing this condition.

The authors declared having no competing interests.