Montazeri K. et al. - Photobiomodulation for Mood Disorders: A Systematic Review

This systematic review includes 16 studies on photobiomodulation for mood disorders, including only 4 randomized controlled trials. The authors assign a strong level of recommendation for moderate major depression but consider the evidence insufficient for bipolar disorder.

What this study measured

Katayoon Montazeri and her co-authors searched Google Scholar, PubMed, Scopus, and ScienceDirect using the PRISMA methodology. They included human and animal studies published in English between January 2009 and August 2021. The objective was threefold: to identify the photobiomodulation parameters actually used, to assess the level of evidence supporting their efficacy, and to derive a level of clinical recommendation. This is a systematic review and not a meta-analysis. Therefore, no overall effect was calculated by statistically pooling the trial data.

Key Findings

Sixteen studies met the inclusion criteria, including four randomized controlled trials whose methodological quality was assessed.

• 16 studies were included, including 4 randomized controlled trials.
• Period covered: January 2009 through August 2021; four databases were searched.
• Most commonly used infrared wavelengths: 800 to 830 nm.
• Most commonly used power density: 250 mW/cm².
• Most commonly used energy density: 60 to 120 J/cm².
• Two of the four randomized trials were judged to be of good quality following an assessment of the risk of bias.
• According to the recommendation framework adopted by the authors, photobiomodulation is classified as “strongly recommended” for moderate major depression and “recommended” for anxiety disorders.
• With regard to bipolar disorder, the authors conclude that further studies are needed before any recommendations can be made.

How Transcranial Photobiomodulation Works

The mechanistic hypotheses proposed in this field have yet to be confirmed. Near-infrared light is thought to be absorbed by cytochrome c oxidase, an enzyme in the mitochondrial respiratory chain, which is believed to result in increased ATP production in target tissues. Other mechanisms are being discussed: modulation of cerebral blood flow, a reduction in oxidative stress, and a reduction in neuroinflammation. This review lists irradiation parameters and clinical results; it does not directly measure these mechanisms.

Limits You Should Know

The main limitation relates to the evidence base: sixteen studies, including four randomized trials, and only two of which are of high methodological quality. The review combines human and animal studies, which makes clinical extrapolation challenging. Since no pooled effect was calculated, the magnitude of the benefit remains unknown. The search ended in August 2021 and therefore does not include subsequent publications. Finally, the heterogeneity of the parameters makes it impossible to identify a single protocol, and the proposed level of recommendation reflects the authors’ assessment rather than solidly established evidence of efficacy.

What This Means in Practice

This review summarizes the published findings and highlights areas of research interest regarding depression and anxiety, without providing a validated protocol. Photobiomodulation is not a substitute for psychiatric care or ongoing treatment: a mood disorder requires professional support. The most prudent course of action is to discuss this with your primary care physician or psychiatrist, who is familiar with your medical history and the treatment you are already receiving.

Frequently Asked Questions

What wavelengths are used to treat mood disorders?

In the studies reviewed, infrared wavelengths ranging from 800 to 830 nm are the most common. The authors also note a power density of 250 mW/cm² and an energy density of 60 to 120 J/cm². These values describe published data; they do not constitute a recommendation.

Is this review a meta-analysis?

No. This is a systematic review conducted in accordance with PRISMA guidelines, without statistical pooling of the results. Therefore, no overall effect size is available. This is an important distinction: the review describes and evaluates the studies; it does not quantify an average benefit.

What do we know about bipolar disorder?

Very little. The authors explicitly state that the available data do not support a recommendation for this indication. Further studies are needed. Bipolar disorder requires specialized psychiatric care.

Reference

Montazeri K, Farhadi M, Fekrazad R, Chaibakhsh S, Mahmoudian S. Photobiomodulation therapy in mood disorders: a systematic review. Lasers in Medical Science, 2022; 37 (9): 3343-3351. PMID 36404359. DOI 10.1007/s10103-022-03641-w. https://doi.org/10.1007/s10103-022-03641-w

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.