Review of transcranial photobiomodulation for major depressive disorder: targeting brain metabolism, inflammation, oxidative stress, and neurogenesis

Photobiomodulation with non-thermal lasers: Mechanisms of action and therapeutic uses in dermatology and aesthetic medicine

BACKGROUND

Non-thermal laser therapy in dermatology, is a growing field in medical technology by which therapeutic effects are achieved by exposing tissues to specific wavelengths of light.

OBJECTIVES

The purpose of this review was to gain a better understanding of the science behind non-thermal laser and the evidence supporting its use in dermatology.

METHODS

A group of dermatologists and surgeons recently convened to review the evidence supporting the use of non-thermal laser for body sculpting, improving the appearance of cellulite, and treating onychomycosis.

RESULTS

The use of non-thermal laser for body sculpting is supported by three randomized, double-blind, sham-controlled studies (N = 161), one prospective open-label study (N = 54), and two retrospective studies (N = 775). Non-thermal laser application for improving the appearance of cellulite is supported by one randomized, double-blind, sham-controlled study (N = 38). The use of non-thermal laser for the treatment of onychomycosis is supported by an analysis of three non-randomized, open-label studies demonstrating clinical improvement of nails (N = 292).

CONCLUSIONS

Non-thermal laser is steadily moving into mainstream medical practice, such as dermatology. Although present studies have demonstrated the safety and efficacy of non-thermal laser for body sculpting, cellulite reduction and onychomycosis treatment, studies demonstrating the efficacy of non-thermal laser as a stand-alone procedure are still inadequate.

Photobiomodulation and the brain: a new paradigm

Transcranial photobiomodulation (PBM) also known as low level laser therapy (tLLLT) relies on the use of red/NIR light to stimulate, preserve and regenerate cells and tissues. The mechanism of action involves photon absorption in the mitochondria (cytochrome c oxidase), and ion channels in cells leading to activation of signaling pathways, up-regulation of transcription factors, and increased expression of protective genes. We have studied PBM for treating traumatic brain injury (TBI) in mice using a NIR laser spot delivered to the head. Mice had improved memory and learning, increased neuroprogenitor cells in the dentate gyrus and subventricular zone, increased BDNF and more synaptogenesis in the cortex. These highly beneficial effects on the brain suggest that the applications of tLLLT are much broader than at first conceived. Other groups have studied stroke (animal models and clinical trials), Alzheimer's disease, Parkinson's disease, depression, and cognitive enhancement in healthy subjects.

Multi-Watt Near-Infrared Phototherapy for the Treatment of Comorbid Depression: An Open-Label Single-Arm Study

BACKGROUND

The treatment of depression has been hampered by low efficacy of antidepressant medications and safety concerns with alternative modalities. Recent work demonstrated that multi-Watt transcranial near-infrared light therapy (NILT) can effectively treat traumatic brain injury (TBI). The current objective is to explore multi-Watt NILT efficacy in a proof-of-concept study as a treatment for depression.

METHODS

Thirty-nine sequential patients treated for TBI between March 2013 and May 2017 provided depression self-assessment data and/or were administered the Hamilton depression rating scale. Each completed the Quick Inventory of Depression Symptomatology-Self Report (QIDS) before and after treatment. Patients received multi-Watt NILT using near-infrared lasers (810/980 nm at 8-15 W) applied to forehead and temporal regions bilaterally for 9-12 min to each area. Pre- and posttreatment scores were analyzed by paired t-tests.

RESULTS

All met QIDS criteria for mild to severe depression and 69% had prior antidepressant trials. For 36 of the 39 patients, after 16.82 ± 6.26 treatments, QIDS scores indicated a robust response (decrease of QIDS total score by ≥50%). For 32 of 39 patients, posttreatment QIDS scores indicated a remission from depression (decrease of QIDS total score ≤5). Overall, the QIDS score fell from 14.10 ± 3.39 to 3.41 ± 3.30 SD (p = 6.29 × 10^-19). With 12 or fewer treatments, QIDS score dropped from 14.83 ± 2.55 to 4.17 ± 3.93. Patients receiving ≥13 treatments showed a change in QIDS score from 13.67 ± 3.64 to 3.11 ± 3.14. Those (N = 15) who received the entire treatment course within ≤8 weeks (5.33 ± 1.72 weeks) showed a change in QIDS score from 13.86 ± 3.14 to 4.5 ± 3.94. Suicidal ideation resolved in all, but two patients. Patients remained in remission for up to 55 months after a single course of treatment.

CONCLUSION

This is the first report of high-powered NILT showing efficacy for depression. Multi-Watt NILT showed far greater efficacy and persistent benefit compared to low-power (<1 Watt) infrared light treatments. Patients saw benefit often within four treatments and resolution of depressive symptoms occurred within 4 weeks for some. These data raise an intriguing possibility-that multi-Watt NILT may be a safe, effective, and rapid treatment for depression comorbid with TBI and possibly primary major depression disorder. A double-blind, placebo controlled trial is warranted to verify these proof-of-concept data.

Shining light on the head: Photobiomodulation for brain disorders

Photobiomodulation (PBM) describes the use of red or near-infrared light to stimulate, heal, regenerate, and protect tissue that has either been injured, is degenerating, or else is at risk of dying. One of the organ systems of the human body that is most necessary to life, and whose optimum functioning is most worried about by humankind in general, is the brain. The brain suffers from many different disorders that can be classified into three broad groupings: traumatic events (stroke, traumatic brain injury, and global ischemia), degenerative diseases (dementia, Alzheimer's and Parkinson's), and psychiatric disorders (depression, anxiety, post traumatic stress disorder). There is some evidence that all these seemingly diverse conditions can be beneficially affected by applying light to the head. There is even the possibility that PBM could be used for cognitive enhancement in normal healthy people. In this transcranial PBM (tPBM) application, near-infrared (NIR) light is often applied to the forehead because of the better penetration (no hair, longer wavelength). Some workers have used lasers, but recently the introduction of inexpensive light emitting diode (LED) arrays has allowed the development of light emitting helmets or "brain caps". This review will cover the mechanisms of action of photobiomodulation to the brain, and summarize some of the key pre-clinical studies and clinical trials that have been undertaken for diverse brain disorders.