Urata M. et al. - Changes in depression symptoms following photobiomodulation

Share this article:

This analysis examined 21 patients with depression who underwent transcranial photobiomodulation for eight weeks: only 4 responded to the treatment. Sleep and appetite symptoms improved, while depressive mood and lack of energy persisted in approximately 80 to 90 percent of the patients.

What this study measured

This is an analysis of individual symptoms based on two trials; it is neither a meta-analysis nor a randomized placebo-controlled trial. The data come from the studies “Evaluation of the Therapeutic Effect of Light-Emitting Diodes in Depression 2” and “Evaluation of the Therapeutic Effect of Light-Emitting Diodes in Depression 3,” which involved patients with major depressive disorder.

Participants received transcranial photobiomodulation applied to regions F3 and F4 of the scalp for eight weeks. Symptoms were assessed weekly using the Quick Inventory for Depression Symptomatology (QIDS). Treatment response was defined as a reduction of at least 50% in the QIDS score at eight weeks compared to baseline.

Key Findings

The goal was to describe which symptoms change over time, not to demonstrate the overall effectiveness of the treatment.

21 patients analyzed
4 patients who responded at eight weeks
Autonomic symptoms, including sleep disturbances and changes in appetite: improvement in at least 50% of patients who had these symptoms at baseline
Core depressive symptoms, depressed mood, and lack of energy: persist in approximately 80 to 90 percent of patients
Among responders: a more than 75% improvement in these core symptoms
Duration of the protocol: 8 weeks, with weekly evaluations

The abstract does not provide the wavelength, dose, session duration, p-value, or confidence interval.

How photobiomodulation works for this indication

The proposed mechanisms remain hypothetical. Near-infrared light applied to the scalp could reach the prefrontal cortex and be absorbed by mitochondrial cytochrome c oxidase, which could increase ATP production in the exposed neurons. Other proposed mechanisms include effects on local cerebral blood flow, oxidative stress, and modulation of inflammation. None of these mechanisms were measured in this analysis, and there is no evidence to suggest that they explain the observed changes.

Limits You Should Know

The primary outcome is weak: 4 responders out of 21 patients. The sample size is small, and the analysis is exploratory, examining symptoms one by one, which increases the number of statistical comparisons. The abstract does not describe a control group or a comparison with an inactive device, so spontaneous improvement and the placebo effect cannot be ruled out. The light parameters are not specified. The authors themselves note that larger samples will be needed to assess the efficacy of this approach.

What This Means in Practice

Based on this data, photobiomodulation cannot be considered a treatment for depression. Depression is a treatable condition that requires medical or psychiatric care. Photobiomodulation is not a substitute for such care, psychotherapy, or ongoing medication. No treatment should be stopped or changed without consulting the prescribing physician. If symptoms worsen, or if you experience suicidal thoughts or distress, contact a healthcare professional or emergency services immediately.

Frequently Asked Questions

Does transcranial photobiomodulation treat depression?

This analysis does not demonstrate this. Of 21 patients, only 4 saw their QIDS score decrease by half at eight weeks. This is a small, exploratory study—with no described comparison to an inactive device—and not a trial that would allow for conclusions about efficacy.

Which symptoms showed the greatest change in this study?

The so-called autonomic nervous system symptoms—that is, sleep disturbances and changes in appetite—improved in at least half of the patients who had them at the start of the study. In contrast, depressive mood and low energy persisted in approximately 80 to 90 percent of the patients. In the four responders, these core symptoms improved by more than 75%.

Can light therapy be used as a supplement to antidepressant treatment?

This question should be directed to the treating physician. No data from this study support recommending such a combination or rule out the risks associated with it. What is certain is that a prescribed treatment should never be stopped or changed on one’s own initiative.

Reference

Urata M, Cassano P, Norton R, Sylvester KM, Watanabe K, Iosifescu DV, Sakurai H. Trajectories of Individual Depressive Symptoms over Time during Transcranial Photobiomodulation. Photonics, 2023;10(12):1324. Article not indexed in PubMed; no PMID available. DOI 10.3390/photonics10121324. https://doi.org/10.3390/photonics10121324

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.