Treating neuropathic pain and comorbid affective disorders: Preclinical and clinical evidence.

INTRODUCTION: Neuropathic pain (NP) significantly impacts quality of life and often coexists with affective disorders such as anxiety and depression. Addressing both NP and its psychiatric manifestations requires a comprehensive understanding of therapeutic options. This study aimed to review the main pharmacological and non-pharmacological treatments for NP and comorbid affective disorders to describe their mechanisms of action and how they are commonly used in clinical practice. METHODS: A review was conducted across five electronic databases, focusing on pharmacological and non-pharmacological treatments for NP and its associated affective disorders. The following combination of Mesh and title/abstract keywords were used: "neuropathic pain," "affective disorders," "depression," "anxiety," "treatment," and "therapy." Both animal and human studies were included to discuss the underlying therapeutic mechanisms of these interventions. RESULTS: Pharmacological interventions, including antidepressants, anticonvulsants, and opioids, modulate neural synaptic transmission to alleviate NP. Topical agents, such as capsaicin, lidocaine patches, and botulinum toxin A, offer localized relief by desensitizing pain pathways. Some of these drugs, especially antidepressants, also treat comorbid affective disorders. Non-pharmacological techniques, including repetitive transcranial magnetic stimulation, transcranial direct current stimulation, and photobiomodulation therapy, modulate cortical activity and have shown promise for NP and mood disorders. CONCLUSIONS: The interconnection between NP and comorbid affective disorders necessitates holistic therapeutic strategies. Some pharmacological treatments can be used for both conditions, and non-pharmacological interventions have emerged as promising complementary approaches. Future research should explore novel molecular pathways to enhance treatment options for these interrelated conditions.

Neuropathic pain, mood, and stress-related disorders: A literature review of comorbidity and co-pathogenesis.

Neuropathic pain can be caused by multiple factors, and its prevalence can reach 10% of the global population. It is becoming increasingly evident that limited or short-lasting response to treatments for neuropathic pain is associated with psychological factors, which include psychiatric comorbidities known to affect quality of life. It is estimated that 60% of patients with neuropathic pain also experience depression, anxiety, and stress symptoms. Altered mood, including stress, can be a consequence of several painful conditions but can also favor pain chronicization when preexisting. Despite the apparent tight connection between clinical pain and mood/stress disorders, the exact physiological mechanisms remain unclear. This review aims to provide an overview of state-of-the-art research on the mechanisms of pain related to the pathophysiology of depression, anxiety, and stress disorders.

Inflammation in obsessive-compulsive disorder: A literature review and hypothesis-based potential of transcranial photobiomodulation.

Obsessive-compulsive disorder (OCD) is a disabling neuropsychiatric disorder that affects about 2%-3% of the global population. Despite the availability of several treatments, many patients with OCD do not respond adequately, highlighting the need for new therapeutic approaches. Recent studies have associated various inflammatory processes with the pathogenesis of OCD, including alterations in peripheral immune cells, alterations in cytokine levels, and neuroinflammation. These findings suggest that inflammation could be a promising target for intervention. Transcranial photobiomodulation (t-PBM) with near-infrared light is a noninvasive neuromodulation technique that has shown potential for several neuropsychiatric disorders. However, its efficacy in OCD remains to be fully explored. This study aimed to review the literature on inflammation in OCD, detailing associations with T-cell populations, monocytes, NLRP3 inflammasome components, microglial activation, and elevated proinflammatory cytokines such as TNF-α, CRP, IL-1ß, and IL-6. We also examined the hypothesis-based potential of t-PBM in targeting these inflammatory pathways of OCD, focusing on mechanisms such as modulation of oxidative stress, regulation of immune cell function, reduction of proinflammatory cytokine levels, deactivation of neurotoxic microglia, and upregulation of BDNF gene expression. Our review suggests that t-PBM could be a promising, noninvasive intervention for OCD, with the potential to modulate underlying inflammatory processes. Future research should focus on randomized clinical trials to assess t-PBM's efficacy and optimal treatment parameters in OCD. Biomarker analyses and neuroimaging studies will be important in understanding the relationship between inflammatory modulation and OCD symptom improvement following t-PBM sessions.

A Randomized Controlled Trial of Community-Delivered Heated Hatha Yoga for Moderate-to-Severe Depression.

Objective: To evaluate feasibility, acceptability, and preliminary efficacy of heated yoga to treat moderate-to-severe depression.Design: An 8-week randomized controlled trial (RCT) of heated yoga versus waitlist control was conducted from March 2017 to August 2019.Methods: Participants in the yoga condition were asked to attend heated yoga classes at 2 community heated yoga studios at least twice weekly. We assessed acceptability and feasibility using exit interview and attendance data, respectively. The primary intervention efficacy outcome variable was change in the Inventory of Depressive Symptomatology-Clinician Rated (IDS-CR) score from baseline to post-intervention (week 8).Results: We randomized 80 participants and included 65 (mean [± SD] age 32.7 [± 11.7] years; 81.5% female) in the analyses (yoga n = 33, waitlist n = 32). The mean IDS-CR score at baseline was 35.6 (± 7.9) for the full sample, 36.9 (± 8.8) for yoga participants, and 34.4 (± 6.7) for waitlist participants. Participants attended an average of 10.3 (± 7.1) total classes over the 8-week intervention period. Yoga participants had a significantly greater pre- to post-intervention reduction in IDS-CR scores than waitlist participants (Cohen d = 1.04, P < .001). More yoga participants (59.3%; n = 16) than waitlist participants (6.3%; n = 2) evidenced larger treatment responses (IDS-CR ≥ 50% decrease in symptoms). Participants rated the heated yoga and its aftereffects positively in exit interviews.Conclusions: Approximately 1 heated yoga session per week (mean of 10.3 classes over 8 weeks) was associated with significantly greater reduction in depression symptoms than a waitlist control. Participants rated heated yoga positively. Taken together, results suggest feasibility, acceptability, and preliminary efficacy for patients with depression and warrant further research using active control conditions.Trial Registration: ClinicalTrials.gov identifier: NCT02607514.

Protocol Report on the Transcranial Photobiomodulation for Alzheimer's Disease (TRAP-AD) Study.

BACKGROUND: Alzheimer's disease's (AD) prevalence is projected to increase as the population ages and current treatments are minimally effective. Transcranial photobiomodulation (t-PBM) with near-infrared (NIR) light penetrates into the cerebral cortex, stimulates the mitochondrial respiratory chain, and increases cerebral blood flow. Preliminary data suggests t-PBM may be efficacious in improving cognition in people with early AD and amnestic mild cognitive impairment (aMCI). METHODS: In this randomized, double-blind, placebo-controlled study with aMCI and early AD participants, we will test the efficacy, safety, and impact on cognition of 24 sessions of t-PBM delivered over 8 weeks. Brain mechanisms of t-PBM in this population will be explored by testing whether the baseline tau burden (measured with 18F-MK6240), or changes in mitochondrial function over 8 weeks (assessed with 31P-MRSI), moderates the changes observed in cognitive functions after t-PBM therapy. We will also use changes in the fMRI Blood-Oxygenation-Level-Dependent (BOLD) signal after a single treatment to demonstrate t-PBM-dependent increases in prefrontal cortex blood flow. CONCLUSION: This study will test whether t-PBM, a low-cost, accessible, and user-friendly intervention, has the potential to improve cognition and function in an aMCI and early AD population.

Photobiomodulation: An Emerging Treatment Modality for Depression.

Major depressive disorder (MDD) is considered a global crisis. Conventional treatments for MDD consist of pharmacotherapy and psychotherapy, although a significant number of patients with depression respond poorly to conventional treatments and are diagnosed with treatment-resistant depression (TRD). Transcranial photobiomodulation (t-PBM) therapy uses near-infrared light, delivered transcranially, to modulate the brain cortex. The aim of this review was to revisit the antidepressant effects of t-PBM, with a special emphasis on individuals with TRD. A search on PubMed and ClinicalTrials.gov tracked clinical studies using t-PBM for the treatment of patients diagnosed with MDD and TRD.

Photobiomodulation for Major Depressive Disorder: Linking Transcranial Infrared Light, Biophotons and Oxidative Stress.

ABSTRACT: Incompletely treated major depressive disorder (MDD) poses an enormous global health burden. Conventional treatment for MDD consists of pharmacotherapy and psychotherapy, though a significant number of patients do not achieve remission with such treatments. Transcranial photobiomodulation (t-PBM) is a promising novel therapy that uses extracranial light, especially in the near-infrared (NIR) and red spectra, for biological and therapeutic effects. The aims of this Review are to evaluate the current clinical and preclinical literature on t-PBM in MDD and to discuss candidate mechanisms for effects of t-PBM in MDD, with specific attention to biophotons and oxidative stress. A search on PubMed and ClinicalTrials.gov identified clinical and preclinical studies using t-PBM for the treatment of MDD as a primary focus. After a systematic screening, only 19 studies containing original data were included in this review (9 clinical and 10 preclinical trials). Study results demonstrate consensus that t-PBM is a safe and potentially effective treatment; however, varying treatment parameters among studies complicate definitive conclusions about efficacy. Among other mechanisms of action, t-PBM stimulates the complex IV of the mitochondrial respiratory chain and induces an increase in cellular energy metabolism. We suggest that future trials include biological measures to better understand the mechanisms of action of t-PBM and to optimize treatment efficiency. Of particular interest going forward will be studying potential effects of t-PBM-an external light source on the NIR spectra-on neural circuitry implicated in depression.

Very Low-Level Transcranial Photobiomodulation for Major Depressive Disorder: The ELATED-3 Multicenter, Randomized, Sham-Controlled Trial.

Background: Transcranial photobiomodulation (t-PBM) with near-infrared (NIR) light might represent a treatment for major depressive disorder (MDD). However, the dosimetry of administered t-PBM varies widely. We tested the efficacy of t-PBM with low irradiance, low energy per session, and low number of sessions in individuals with MDD.Methods: A 2-site, double-blind, sham-controlled study was conducted of adjunct t-PBM NIR (830 nm; continuous wave; 35.8 cm2 treatment area; 54.8 mW/cm2 irradiance; 65.8 J/cm2 fluence, 20 min/session; ~2 W total power; 2.3 kJ total energy per session), delivered to the prefrontal cortex, bilaterally, twice a week for 6 weeks, in subjects diagnosed with MDD per the DSM-IV criteria. Subjects were recruited between August 2016 and May 2018. A sequential parallel comparison design was used: 18 nonresponders to sham in phase 1 (6 weeks) were re-randomized in phase 2. The primary outcome was reduction in depression severity (Hamilton Depression Rating Scale [HDRS-17] and Quick Inventory of Depressive Symptomatology-Clinician Rating [QIDS-C] scores) from baseline. Statistical analyses used R package SPCDAnalyze2, including all subjects with ≥ 1 post-randomization evaluation.Results: Of the 54 subjects recruited, we included 49 MDD subjects in the analysis (71% female, mean ± SD age 40.8 ± 16.1 years). There were no significant differences between t-PBM and sham with respect to the change in HDRS-17 (t = -0.319, P = .751) or QIDS-C (t = -0.499, P = .620) scores. The sham effect was reasonably low.Conclusions: Mostly uncontrolled studies suggest the efficacy of t-PBM for MDD; however, its optimal dose is still to be defined. A minimal dose threshold is likely necessary, similarly to other neuromodulation techniques in MDD (electroconvulsive therapy, transcranial magnetic stimulation). We established a threshold of inefficacy of t-PBM for MDD, based on combined low irradiance, low energy per session, and low number of sessions.Trial Registration: ClinicalTrials.gov identifier: NCT02959307.

Transcranial Photobiomodulation in Adults with High-Functioning Autism Spectrum Disorder: Positive Findings from a Proof-of-Concept Study.

Objective: To assess the efficacy and safety of transcranial photobiomodulation (tPBM) in adults with autism spectrum disorder (ASD). Methods: Adults with high-functioning-ASD, between 18 and 59 years of age, were enrolled to receive twice a week tPBM for 8 weeks in an open-label single group design. ASD symptom severity was assessed at baseline, midpoint, and end-point, by clinician-, self-, and informant-rated measures. Treatment response was defined as a ≥30% reduction in Social Responsiveness Scale-2nd Edition (SRS-2) total score and ASD Clinical Global Impression-Improvement score ≤2. Any possible adverse events were recorded at each visit. Paired-samples t-test analyses were performed. Results: Eleven participants were enrolled, and 10 participants (9 males; 30.0 ± 11.9 years) completed the study. One participant withdrew consent before baseline. All 10 completers were included in efficacy and safety analyses. Five participants (50%) met responder criteria at end-point. Overall, 8-week tPBM was associated with significant reduction in SRS-2 total scores at end-point (SRS-2: -30.6 ± 23, p < 0.001) particularly in Social Awareness (-3.0 ± 1.9, p < 0.001), Social Communication (-10.3 ± 6, p < 0.001), Social Motivation (-5.0 ± 2.4, p < 0.001), and Restricted/Repetitive Behaviors (-7.4 ± 4.1, p < 0.001). There were statistically significant improvements at end-point in Global Assessment of Functioning scores (+12.8 ± 4.2, p < 0.001) and Quality of Life Enjoyment and Satisfaction Questionnaire scores (+6.0 ± 7.9, p = 0.02). Three participants experienced transient, mild side effects (insomnia, headache, and warmth at treatment application site). No adverse events required changes in tPBM protocol. Adherence rate was 98%. Conclusions: tPBM is a safe and feasible treatment approach that has the potential to treat core features of ASD. Further research is necessary and warranted. ClinicalTrials.gov Identifier: NCT03724552.

Treatment of Kleine-Levin Syndrome With Intranasal Photobiomodulation and Methylene Blue.

Kleine-Levin syndrome (KLS) is a rare neuropsychiatric disorder, characterized by recurrent episodes of idiopathic hypersomnia, and cognitive and behavioral abnormalities, such as memory loss and child-like language. There is no definitive etiology for KLS; however, there are hypotheses of genetic predisposition, autoimmune mechanisms, and abnormal thalamic and hypothalamic functioning. Similarly, there is no definitive treatment for KLS as one method may be beneficial for one patient and not for another. We present a case of KLS in a patient who has no clinical improvement in symptoms with a variety of treatments. The parents of the patient agreed to attempt a trial of intranasal photobiomodulation (i-PBM) with red light, in combination with methylene blue (MB). The patient showed remission of the KLS episode following treatment with no further KLS episodes reported after treatment.

Transitioning From In-Person to Remote Clinical Research on Depression and Traumatic Brain Injury During the COVID-19 Pandemic: Study Modifications and Preliminary Feasibility From a Randomized Controlled Pilot Study.

BACKGROUND: Telehealth has provided many researchers, especially those conducting psychosocial research, with the tools necessary to transition from in-person to remote clinical trials during the COVID-19 pandemic. A growing body of research supports the effectiveness of telemental health for a variety of psychiatric conditions, but few studies have examined telemental health for individuals with comorbid medical diagnoses. Furthermore, little is known about the remote implementation of clinical trials examining telemental health interventions. OBJECTIVE: This paper outlines the procedural modifications used to facilitate conversion of an in-person randomized controlled trial of cognitive behavioral therapy (CBT) for depression in individuals with traumatic brain injury (TBI; CBT-TBI) to a telemental health study administered remotely. METHODS: Given the nature of remote implementation and specific challenges experienced by individuals with TBI, considerations related to treatment delivery, remote consent, data management, neuropsychological assessment, safety monitoring, and delivery of supportive material have been discussed. Feasibility, acceptability, and safety were evaluated by examining attendance and participant responses on self-report measures of treatment satisfaction and suicidal behavior. RESULTS: High rates of treatment attendance, assessment completion, study retention, and satisfaction with the intervention and modality were reported by participants who completed at least one telemental health CBT-TBI session. CONCLUSIONS: Study modifications are necessary when conducting a study remotely, and special attention should be paid to comorbidities and population-specific challenges (eg, cognitive impairment). Preliminary data support the feasibility, acceptability, and safety of remotely conducting a randomized controlled trial of CBT-TBI. TRIAL REGISTRATION: ClinicalTrials.gov NCT03307070; https://clinicaltrials.gov/ct2/show/NCT03307070.

Dosimetry and Clinical Efficacy of Transcranial Photobiomodulation for Major Depression Disorder: Could they Guide Dosimetry for Alzheimer's Disease?

BACKGROUND: Major depressive disorder (MDD) is prevalent and has significant impact on individuals and society. Cognitive symptoms are frequent in MDD and insufficiently treated by antidepressant medications. Transcranial photobiomodulation (t-PBM) is a novel device therapy which shows promise as an antidepressant and pro-cognitive treatment. To date, despite the encouraging results, the optimal stimulation parameters of t-PBM to treat MDD are not established, and clinical studies are very heterogeneous in terms of these parameters. While the literature provides guidance on the appropriate fluence to achieve therapeutic results, little is known on the other parameters. OBJECTIVE: To evaluate the relationship between different parameters and the antidepressant effect of t-PBM. METHODS: We reviewed clinical studies on MDD and on depressive symptoms comorbid with other diseases. We calculated the standardized effect size of the change in symptoms severity before and after t-PBM and we performed a descriptive analysis of the reviewed papers. RESULTS: The greatest effect sizes for the antidepressant effect were found in studies using pulse-wave t-PBM with high peak irradiance (but low average irradiance) over large skin surface. One well-designed and sufficiently powered, double-blind, sham-controlled trial indicated that t-PBM with low irradiance over a small skin surface is ineffective to treat depression. CONCLUSION: The use of t-PBM for Alzheimer's disease and for dementia is still at its inception; these dosimetry lessons from the use of t-PBM for depression might serve as guidance.

Randomized, Placebo-Controlled Trial of the Angiotensin Receptor Antagonist Losartan for Posttraumatic Stress Disorder.

BACKGROUND: Evidence-based pharmacological treatments for posttraumatic stress disorder (PTSD) are few and of limited efficacy. Previous work suggests that angiotensin type 1 receptor inhibition facilitates fear inhibition and extinction, important for recovery from PTSD. This study tests the efficacy of the angiotensin type 1 receptor antagonist losartan, an antihypertensive drug, repurposed for the treatment of PTSD. METHODS: A randomized controlled trial was conducted for 10 weeks in 149 men and women meeting DSM-5 PTSD criteria. Losartan (vs. placebo) was flexibly titrated from 25 to 100 mg/day by week 6 and held at highest tolerated dose until week 10. Primary outcome was the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5) change score at 10 weeks from baseline. A key secondary outcome was change in CAPS-5 associated with a single nucleotide polymorphism of the ACE gene. Additional secondary outcomes included changes in the PTSD Checklist for DSM-5 and the Patient Health Questionnaire-9, and proportion of responders with a Clinical Global Impressions-Improvement scale of "much improved" or "very much improved." RESULTS: Both groups had robust improvement in PTSD symptoms, but there was no significant difference on the primary end point, CAPS-5 measured as week 10 change from baseline, between losartan and placebo (mean change difference, 0.9, 95% confidence interval, -3.2 to 5.0). There was no significant difference in the proportion of Clinical Global Impressions-Improvement scale responders for losartan (58.6%) versus placebo (57.9%), no significant differences in changes in PTSD Checklist for DSM-5 or Patient Health Questionnaire-9, and no association between ACE genotype and CAPS-5 improvement on losartan. CONCLUSIONS: At these doses and durations, there was no significant benefit of losartan compared with placebo for the treatment of PTSD. We discuss implications for failure to determine the benefit of a repurposed drug with strong a priori expectations of success based on preclinical and epidemiological data.

Pilot Study on Dose-Dependent Effects of Transcranial Photobiomodulation on Brain Electrical Oscillations: A Potential Therapeutic Target in Alzheimer's Disease.

BACKGROUND: Transcranial photobiomodulation (tPBM) has recently emerged as a potential cognitive enhancement technique and clinical treatment for various neuropsychiatric and neurodegenerative disorders by delivering invisible near-infrared light to the scalp and increasing energy metabolism in the brain. OBJECTIVE: We assessed whether transcranial photobiomodulation with near-infrared light modulates cerebral electrical activity through electroencephalogram (EEG) and cerebral blood flow (CBF). METHODS: We conducted a single-blind, sham-controlled pilot study to test the effect of continuous (c-tPBM), pulse (p-tPBM), and sham (s-tPBM) transcranial photobiomodulation on EEG oscillations and CBF using diffuse correlation spectroscopy (DCS) in a sample of ten healthy subjects [6F/4 M; mean age 28.6±12.9 years]. c-tPBM near-infrared radiation (NIR) (830 nm; 54.8 mW/cm2; 65.8 J/cm2; 2.3 kJ) and p-tPBM (830 nm; 10 Hz; 54.8 mW/cm2; 33%; 21.7 J/cm2; 0.8 kJ) were delivered concurrently to the frontal areas by four LED clusters. EEG and DCS recordings were performed weekly before, during, and after each tPBM session. RESULTS: c-tPBM significantly boosted gamma (t = 3.02, df = 7, p < 0.02) and beta (t = 2.91, df = 7, p < 0.03) EEG spectral powers in eyes-open recordings and gamma power (t = 3.61, df = 6, p < 0.015) in eyes-closed recordings, with a widespread increase over frontal-central scalp regions. There was no significant effect of tPBM on CBF compared to sham. CONCLUSION: Our data suggest a dose-dependent effect of tPBM with NIR on cerebral gamma and beta neuronal activity. Altogether, our findings support the neuromodulatory effect of transcranial NIR.

Low-Dose Testosterone Augmentation for Antidepressant-Resistant Major Depressive Disorder in Women: An 8-Week Randomized Placebo-Controlled Study.

OBJECTIVE: Low-dose testosterone has been shown to improve depression symptom severity, fatigue, and sexual function in small studies in women not formally diagnosed with major depressive disorder. The authors sought to determine whether adjunctive low-dose transdermal testosterone improves depression symptom severity, fatigue, and sexual function in women with antidepressant-resistant major depression. A functional MRI (fMRI) substudy examined effects on activity in the anterior cingulate cortex (ACC), a brain region important in mood regulation. METHODS: The authors conducted an 8-week randomized double-blind placebo-controlled trial of adjunctive testosterone cream in 101 women, ages 21-70, with antidepressant-resistant major depression. The primary outcome measure was depression symptom severity as assessed by the Montgomery-Åsberg Depression Rating Scale (MADRS). Secondary endpoints included fatigue, sexual function, and safety measures. The primary outcome of the fMRI substudy (N=20) was change in ACC activity. RESULTS: The participants' mean age was 47 years (SD=14) and their mean baseline MADRS score was 26.6 (SD=5.9). Eighty-seven (86%) participants completed 8 weeks of treatment. MADRS scores decreased in both study arms from baseline to week 8 (testosterone arm: from 26.8 [SD=6.3] to 15.3 [SD=9.6]; placebo arm: from 26.3 [SD=5.4] to 14.4 [SD=9.3]), with no significant difference between groups. Improvement in fatigue and sexual function did not differ between groups, nor did side effects. fMRI results showed a relationship between ACC activation and androgen levels before treatment but no difference in ACC activation with testosterone compared with placebo. CONCLUSIONS: Adjunctive transdermal testosterone, although well tolerated, was not more effective than placebo in improving symptoms of depression, fatigue, or sexual dysfunction. Imaging in a subset of participants demonstrated that testosterone did not result in greater activation of the ACC.

Transcranial photobiomodulation with near-infrared light from childhood to elderliness: simulation of dosimetry.

Significance: Major depressive disorder (MDD) affects over 40 million U.S. adults in their lifetime. Transcranial photobiomodulation (t-PBM) has been shown to be effective in treating MDD, but the current treatment dosage does not account for head and brain anatomical changes due to aging. Aim: We study effective t-PBM dosage and its variations across age groups using state-of-the-art Monte Carlo simulations and age-dependent brain atlases ranging between 5 and 85 years of age. Approach: Age-dependent brain models are derived from 18 MRI brain atlases. Two extracranial source positions, F3-F4 and Fp1-Fpz-Fp2 in the EEG 10-20 system, are simulated at five selected wavelengths and energy depositions at two MDD-relevant cortical regions-dorsolateral prefrontal cortex (dlPFC) and ventromedial prefrontal cortex (vmPFC)-are quantified. Results: An overall decrease of energy deposition was found with increasing age. A strong negative correlation between the thickness of extracerebral tissues (ECT) and energy deposition was observed, suggesting that increasing ECT thickness over age is primarily responsible for reduced energy delivery. The F3-F4 position appears to be more efficient in reaching dlPFC compared to treating vmPFC via the Fp1-Fpz-Fp2 position. Conclusions: Quantitative simulations revealed age-dependent light delivery across the lifespan of human brains, suggesting the need for personalized and age-adaptive t-PBM treatment planning.

Therapeutic potential of intranasal photobiomodulation therapy for neurological and neuropsychiatric disorders: a narrative review.

The application of photobiomodulation therapy (PBMT) for neuronal stimulation is studied in different animal models and in humans, and has shown to improve cerebral metabolic activity and blood flow, and provide neuroprotection via anti-inflammatory and antioxidant pathways. Recently, intranasal PBMT (i-PBMT) has become an attractive and potential method for the treatment of brain conditions. Herein, we provide a summary of different intranasal light delivery approaches including a nostril-based portable method and implanted deep-nasal methods for the effective systemic or direct irradiation of the brain. Nostril-based i-PBMT devices are available, using either lasers or light emitting diodes (LEDs), and can be applied either alone or in combination to transcranial devices (the latter applied directly to the scalp) to treat a wide range of brain conditions such as mild cognitive impairment, Alzheimer's disease, Parkinson's disease, cerebrovascular diseases, depression and anxiety as well as insomnia. Evidence shows that nostril-based i-PBMT improves blood rheology and cerebral blood flow, so that, without needing to puncture blood vessels, i-PBMT may have equivalent results to a peripheral intravenous laser irradiation procedure. Up to now, no studies were conducted to implant PBMT light sources deep within the nose in a clinical setting, but simulation studies suggest that deep-nasal PBMT via cribriform plate and sphenoid sinus might be an effective method to deliver light to the ventromedial part of the prefrontal and orbitofrontal cortex. Home-based i-PBMT, using inexpensive LED applicators, has potential as a novel approach for neurorehabilitation; comparative studies also testing sham, and transcranial PBMT are warranted.

Reported Side Effects, Weight and Blood Pressure, After Repeated Sessions of Transcranial Photobiomodulation.

Background: Transcranial photobiomodulation (t-PBM) consists in the delivery of near-infrared light (NIR) to the scalp, directed to cortical areas of the brain. NIR t-PBM recently emerged as a potential therapy for depression, although safety of repeated treatments has not been adequately explored. Objective: This study assessed incidence of side effects, including weight and blood pressure changes, during repeated sessions of NIR t-PBM using a light-emitting diode source. Methods: We performed a secondary analysis of a double-blind clinical trial on t-PBM for major depressive disorder. Eighteen individuals received NIR t-PBM (n = 9) or sham (n = 9) twice weekly for 8 weeks. Side effects were assessed using the Systematic Assessment for Treatment-Emergent Effects-Specific Inquiry. In 14 individuals (nNIR = 6 vs. nsham = 8), body weight and systemic blood pressure were recorded at baseline and end-point. Results: More subjects in the NIR t-PBM group experienced side effects compared to sham, but only a trend for statistical significance was observed (χ2 = 3.60; df = 1; p = 0.058). The rate of side effects described by participants as "severe" in intensity was low and similar between the treatment groups (χ2 = 0.4; df = 1; p = 0.53), with no serious adverse events. Most side effects resolved during the study and treatment interruption were not required. Changes in weight and systolic blood pressure across groups were neither significant nor approached significance. In the NIR t-PBM group, diastolic blood pressure increased and reached statistical-however not clinical-significance (5.67 ± 7.26 vs. -6.13 ± 6.88; z = -2.40, p = 0.016). Conclusions: This small-sample, exploratory study indicates repeated sessions of NIR t-PBM might be associated with treatment-emergent side effects. The systemic metabolic and hemodynamic profile of repeated t-PBM appeared benign. Future studies with larger samples and longer follow-up are needed to more accurately determine the side-effect profile and safety of NIR t-PBM.

Transcranial Photobiomodulation with Near-Infrared Light for Generalized Anxiety Disorder: A Pilot Study.

Objective: Our aim was to test the anxiolytic effect of transcranial photobiomodulation (t-PBM) with near-infrared light (NIR) in subjects suffering from generalized anxiety disorder (GAD). Background: t-PBM with NIR is an experimental, noninvasive treatment for mood and anxiety disorders. Preliminary evidence indicates a potential anxiolytic effect of transcranial NIR. Methods: Fifteen subjects suffering from GAD were recruited in an open-label 8-week study. Each participant self-administered t-PBM daily, for 20 min (continuous wave; 830 nm peak wavelength; average irradiance 30 mW/cm2; average fluence 36 J/cm2; total energy delivered per session 2.9 kJ: total output power 2.4 W) broadly on the forehead (total area 80 cm2) with an LED-cluster headband (Cerebral Sciences). Outcome measures were the reduction in total scores of the Hamilton Anxiety Scale (SIGH-A), the Clinical Global Impressions-Severity (CGI-S) subscale and the Pittsburgh Sleep Quality Index (PSQI) subscales from baseline to last observation carried forward. Results: Of the 15 recruited subjects (mean age 30 ± 14 years; 67% women), 12 (80%) completed the open trial. Results show a significant reduction in the total scores of SIGH-A (from 17.27 ± 4.89 to 8.47 ± 4.87; p < 0.001; Cohen's d effect size = 1.47), in the CGI-S subscale (from 4.53 ± 0.52 to 2.87 ± 0.83; p < 0.001; Cohen's d effect size = 2.04), as well as significant improvements in sleep at the PSQI. t-PBM was well tolerated with no serious adverse events. Conclusions: Based on our pilot study, t-PBM with NIR is a promising alternative treatment for GAD. Larger, randomized, double-blind, sham-controlled studies are needed.