Noda Y. et al. - Violet light photobiomodulation for mild depression: a randomized controlled trial

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This randomized, double-blind, crossover trial tested glasses emitting pulsed violet light at 40 Hz in 57 patients with mild depression. MADRS scores improved significantly with the active device compared with the sham device, but the confidence interval was near the threshold of statistical significance (95% CI, −2.5 to −0.1; p = 0.042).

What this study measured

This is a single randomized, double-blind, placebo-controlled, crossover trial, not a meta-analysis. It was conducted at a clinic in Tokyo between June 2021 and December 2023 among 57 Japanese outpatients aged 20 to 74 years who had been diagnosed with mild major depression. Each participant wore active glasses for four weeks, followed by a four-week washout period and then four weeks of wearing sham glasses, or vice versa. Ongoing antidepressant treatments were maintained unchanged. The primary endpoint was the change in the MADRS score after four weeks.

Key Findings

The active device outperformed the sham device on the primary endpoint, albeit by a narrow margin. The reported tolerability was good.

57 Japanese outpatients, aged 20 to 74, with mild major depression.
Significant improvement in the MADRS score with active glasses compared with sham glasses: 95% CI -2.5 to -0.1; p = 0.042.
Duration of use: 4 weeks per phase, with a 4-week break between phases.
Pulsed violet light at 40 Hz, delivered through irradiation goggles.
No adverse events related to wearing glasses were observed.
Recruitment took place between June 2021 and December 2023 at a single center.
Trial registration: jRCTs032210260.

How Transcranial Photobiomodulation Works

The hypothesis adopted here differs from that of conventional transcranial photobiomodulation. The authors suggest neuromodulation of the depression network via OPN5, a violet-light-sensitive opsin, with the pathway entering through the eyes rather than the skull. In transcranial photobiomodulation using red and near-infrared light, the proposed mechanisms—which are also hypothetical—involve mitochondrial cytochrome c oxidase and ATP production, modulation of cerebral blood flow, and a reduction in oxidative stress and neuroinflammation. None of these mechanisms were measured in this trial.

Limits You Should Know

The magnitude of the benefit is modest, and the confidence interval approaches zero at its upper bound (-0.1), indicating a fragile result that is barely statistically significant. The sample size of 57 patients and the single-center nature of the study limit the scope of the conclusions, as does the fact that the participants were exclusively Japanese. Only mild major depression was studied: there is no basis for extrapolating to moderate or severe forms. Finally, this study involved violet light delivered via the eyes, a modality distinct from transcranial near-infrared photobiomodulation, and the results are not interchangeable.

What This Means in Practice

The signal is real but weak, and comes from a single trial that requires replication. It should be noted that the participants’ antidepressant treatments were continued throughout the study: the device was tested as an adjunct, never as a replacement. Photobiomodulation is not a substitute for psychiatric care or ongoing treatment, and a mood disorder requires professional support. This topic should be discussed with the treating physician, as only that physician has access to the patient’s full medical record.

Frequently Asked Questions

Are violet-light glasses effective against depression?

This trial reports a significant but modest improvement in MADRS scores for mild depression, with a confidence interval close to zero. This is a single trial involving 57 participants. It is not possible to conclude that the treatment is effective or to guarantee individual benefit.

Is violet light the same thing as transcranial photobiomodulation?

No. In this case, the violet light is delivered to the eyes through glasses, and the mechanistic hypothesis is based on the opsin OPN5. Transcranial photobiomodulation uses red or near-infrared light applied to the skull. The two approaches are not interchangeable.

Did the device cause any adverse effects?

The authors note that no adverse events related to wearing the glasses were observed during the trial. This observation is based on 57 participants and four-week periods. It does not address prolonged use beyond this duration.

Reference

Noda Y, Taniguchi K, Takano M, et al. Violet light photobiomodulation therapy for depression: A double-blind randomized crossover trial. Journal of Affective Disorders, 2025; 376: 325-332. PMID 39961441. DOI 10.1016/j.jad.2025.02.031. https://doi.org/10.1016/j.jad.2025.02.031

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment or psychiatric care. Please consult a healthcare professional.