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TOPLINE:

Light therapy was associated with a greater reduction in symptoms of depression in patients with major depressive disorder (MDD) and subthreshold depression (StD) compared to control therapies, a new systematic review and meta-analysis showed. Light therapy was also linked to improvement in sleep quality and daytime sleepiness.

METHODOLOGY:

• A systematic review and meta-analysis of 19 randomized controlled trials published from 2020 to 2025 included more than 1000 adults (66% women) with nonseasonal MDD, StD , postnatal depression (PND), or sleep disorders.
• Nearly 600 participants received light therapy, including bright light therapy (BLT), violet therapy, or enhanced melanopsin therapy, whereas other participants were exposed to control measures, including inactive equipment, dim red light, and standard light.
• The primary outcome was reduction in depression symptoms. Secondary outcomes included improvements on the Hamilton Anxiety Rating Scale (HAM-A) on objective sleep quality measures, such as total sleep time and sleep efficiency, and on subjective measures, such as the Pittsburgh Sleep Quality Index (PSQI), the Insomnia Severity Index, and the Epworth Sleepiness Scale.
• Subgroup analyses explored possible effects from factors such as age, light therapy duration, illuminance, light color, disorder subtype, and medication status.

TAKEAWAY:

• Depression symptoms after light therapy were reduced significantly in patients with nonseasonal MDD (standardized mean difference [SMD], 0.35; P < .001) and in patients with StD (SMD, 0.9; P < .001), with low and moderate heterogeneity among the respective studies.
• Light therapy duration showed a positive correlation with depression improvement (P = .02), whereas illuminance showed a negative correlation (P = .02). Disorder subtype (P = .04) and medication status (P = .02) also significantly affected the efficacy of light therapy.
• For subjective sleep quality measures, PSQI scores showed significant improvement in participants with PND, MDD, primary insomnia, poststroke insomnia, or Alzheimer’s disease in the light therapy group and in those with Parkinson’s disease in the enhanced melanopsin group. Insomnia scores were significantly reduced after BLT in patients with MDD or poststroke insomnia, and daytime sleepiness scores were decreased in the enhanced melanopsin and BLT groups.
• Posttreatment HAM-A score changes between the BLT and control groups were not significant, and objective sleep measures showed inconsistent results across different populations and interventions.

IN PRACTICE:

Overall, light therapy had a positive effect on depression and subjective sleep quality, the investigators noted.

However, future studies should explore possible influencing factors on its efficacy, “such as light modalities (illuminance, light wavelength, light color, etc.), disease subtypes, control measures, races, ages, treatment duration, medication status, patients’ occupation, patients’ degree of education, temperature, etc,” they added.

SOURCE:

This study was led by Xueyuan Wang, Zhongda Hospital School of Medicine, Southeast University, Nanjing, China. It was published online on May 3 in General Hospital Psychiatry.

LIMITATIONS:

The analysis combined highly heterogeneous populations and light interventions, and the included sample size became smaller in each subtype, leading to imprecision. In some of the studies, patients took psychotropic drugs beforehand, leading to potential bias.

DISCLOSURES:

This study received no funding, and the investigators reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.