Interactions between transcranial direct current stimulation (tDCS) and pharmacological interventions in the Major Depressive Episode: Findings from a naturalistic study

Evaluating the effects of tDCS on depressive and anxiety symptoms from a transdiagnostic perspective: a systematic review and meta-analysis of randomized controlled trials

Depressive and anxiety symptoms are prevalent among patients with various clinical conditions, resulting in diminished emotional well-being and impaired daily functioning. The neural mechanisms underlying these symptoms, particularly across different disorders, remain unclear, limiting the effectiveness of conventional treatments. Therefore, it is crucial to elucidate the neural underpinnings of depressive and anxiety symptoms and investigate novel, effective treatments across clinical conditions. Transcranial direct current stimulation (tDCS) is a neuromodulatory technique that can help understand the neural underpinnings of symptoms and facilitate the development of interventions, addressing the two research gaps at both neural and clinical levels. Thus, this systematic review and meta-analysis aims to evaluate the existing evidence regarding the therapeutic efficacy of tDCS in reducing depressive and anxiety symptoms among individuals with diverse clinical diagnoses. This review evaluated evidence from fifty-six randomized, sham-controlled trials that administered repeated tDCS sessions with a parallel design, applying a three-level meta-analytic model. tDCS targeting the left dorsolateral prefrontal cortex (DLPFC) at 2-mA intensity demonstrates moderate efficacy in alleviating depressive symptoms, identifying the left DLPFC as a transdiagnostic neural mechanism of depressive symptoms across clinical conditions. In comparison, the findings on anxiety symptoms demonstrate greater heterogeneity. tDCS over the left DLPFC is effective in reducing depressive symptoms and shows promising effects in alleviating anxiety symptoms among individuals with diverse diagnoses. These findings enhance our understanding of the neuropsychological basis of depressive and anxiety symptoms, laying the groundwork for the development of more effective tDCS interventions applicable across clinical conditions.

A Review of Transcranial Magnetic Stimulation and Transcranial Direct Current Stimulation Combined with Medication and Psychotherapy for Depression

LEARNING OBJECTIVES

After participating in this CME activity, the psychiatrist should be better able to:• Compare and contrast therapies used in combination with transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) for treating MDD.

BACKGROUND

Noninvasive neuromodulation, such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has emerged as a major area for treating major depressive disorder (MDD). This review has two primary aims: (1) to review the current literature on combining TMS and tDCS with other therapies, such as psychotherapy and psychopharmacological interventions, and (2) to discuss the efficacy, feasibility, limitations, and future directions of these combined treatments for MDD.

METHOD

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched three databases: PubMed, PsycInfo, and Cochrane Library. The last search date was December 5, 2023.

RESULTS

The initial search revealed 2,519 records. After screening and full-text review, 58 studies (7 TMS plus psychotherapy, 32 TMS plus medication, 7 tDCS plus psychotherapy, 12 tDCS plus medication) were included.

CONCLUSIONS

The current literature on tDCS and TMS paired with psychotherapy provides initial support for integrating mindfulness interventions with both TMS and tDCS. Adding TMS or tDCS to stable doses of ongoing medications can decrease MDD symptoms; however, benzodiazepines may interfere with TMS and tDCS response, and antipsychotics can interfere with TMS response. Pairing citalopram with TMS and sertraline with tDCS can lead to greater MDD symptom reduction compared to using these medications alone. Future studies need to enroll larger samples, include randomized controlled study designs, create more uniform protocols for combined treatment delivery, and explore mechanisms and predictors of change.

Home-Use Transcranial Direct Current Stimulation for the Treatment of a Major Depressive Episode: A Randomized Clinical Trial

Importance

Transcranial direct current stimulation (tDCS) is moderately effective for depression when applied by trained staff. It is not known whether self-applied tDCS, combined or not with a digital psychological intervention, is also effective.

Objective

To determine whether fully unsupervised home-use tDCS, combined with a digital psychological intervention or digital placebo, is effective for a major depressive episode.

Design, Setting, and Participants

This was a double-blinded, sham-controlled, randomized clinical trial with 3 arms: (1) home-use tDCS plus a digital psychological intervention (double active); (2) home-use tDCS plus digital placebo (tDCS only), and (3) sham home-use tDCS plus digital placebo (double sham). The study was conducted between April 2021 and October 2022 at participants' homes and at Instituto de Psiquiatria do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Brazil. Included participants were aged 18 to 59 years with major depression and a Hamilton Depression Rating Scale, 17-item version (HDRS-17), score above 16, a minimum of 8 years of education, and access to a smartphone and internet at home. Exclusion criteria were other psychiatric disorders, except for anxiety; neurologic or clinical disorders; and tDCS contraindications.

Interventions

tDCS was administered in 2-mA, 30-minute prefrontal sessions for 15 consecutive weekdays (1-mA, 90-second duration for sham) and twice-weekly sessions for 3 weeks. The digital intervention consisted of 46 sessions based on behavioral therapy. Digital placebo was internet browsing.

Main Outcomes and Measures

Change in HDRS-17 score at week 6.

Results

Of 837 volunteers screened, 210 participants were enrolled (180 [86%] female; mean [SD] age, 38.9 [9.3] years) and allocated to double active (n = 64), tDCS only (n = 73), or double sham (n = 73). Of the 210 participants enrolled, 199 finished the trial. Linear mixed-effects models did not reveal statistically significant group differences in treatment by time interactions for HDRS-17 scores, and the estimated effect sizes between groups were as follows: double active vs tDCS only (Cohen d, 0.05; 95% CI, -0.48 to 0.58; P = .86), double active vs double sham (Cohen d, -0.20; 95% CI, -0.73 to 0.34; P = .47), and tDCS only vs double sham (Cohen d, -0.25; 95% CI, -0.76 to 0.27; P = .35). Skin redness and heat or burning sensations were more frequent in the double active and tDCS only groups. One nonfatal suicide attempt occurred in the tDCS only group.

Conclusions and Relevance

Unsupervised home-use tDCS combined with a digital psychological intervention or digital placebo was not found to be superior to sham for treatment of a major depressive episode in this trial.

Trial Registration

ClinicalTrials.gov Identifier: NCT04889976.

Efficacy of transcranial direct current stimulation for treating anhedonia in patients with depression: A randomized, double-blind, sham-controlled clinical trial

BACKGROUND

Anhedonia, the core symptom of major depressive disorder (MDD), is highly prevalent in patients with depression. Anhedonia is associated with low efficacy of drug treatment, high suicide rates, and poor social function. Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technology that uses constant, low-intensity direct current to treat MDD by regulating cortical activity and neuronal excitability. However, little is known about the efficacy of tDCS for treating anhedonia in patients with depression, and even the existing results of clinical trials are conflicting. In addition, there is no consensus on what brain regions should be targeted by tDCS during the treatment of anhedonia in patients with depression.

OBJECTIVE

This study aimed to evaluate the efficacy and safety of tDCS over the left dorsolateral prefrontal cortex (DLPFC) and right orbitofrontal cortex (OFC) in the improvement of anhedonia in patients with depression and finally identified suitable brain regions to be stimulated during treatment.

METHODS

This randomized, double-blind, sham-controlled clinical trial recruited 70 patients with anhedonia and depressive episodes. Patients were randomly assigned to three groups according to the stimulation site: right orbitofrontal cortex (OFC), left dorsolateral prefrontal cortex (DLPFC), and sham stimulation. Each group received twelve 20-min interventions (ten as primary treatment and two for consolidation). The primary outcome was a decrease in Snaith-Hamilton Pleasure Scale (SHAPS) scores after primary treatment. Evaluations were performed at baseline, post-treatment, and 8-week follow-up.

RESULTS

The depression mood of the three groups of patients at each time point was better than the baseline, but there was no significant difference in the efficacy between the groups (p>0.05). On the basis of the improvement of depression, this study found that tDCS of the DLPFC significantly improved anhedonia (p = 0.028) after primary treatment (2 weeks), and tDCS of the DLPFC and OFC significantly improved social functioning (p = 0.005) at 8-week follow-up.

LIMITATIONS

The sample size of this study was small, with only about 23/24 patients in each group completing the intervention assessments; due to the impact of the COVID-19 epidemic, data analysis was limited by the lack of patients during the follow-up period.

CONCLUSIONS

tDCS of the DLPFC significantly improves anhedonia in depressed patients and is thus a potential adjuvant therapy for anhedonia in these patients.

Efficacy of non-invasive brain stimulation combined with antidepressant medications for depression: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Antidepressants, noninvasive brain stimulation (NIBS), and their combination are commonly used in routine clinical practice. Nevertheless, there is a continuous dispute regarding whether the effectiveness of NIBS in combination with antidepressants exceeds that of antidepressants alone. This meta-analysis aimed to evaluate the existing evidence and draw a definitive conclusion on this issue.

METHODS

We conducted a comprehensive search of five databases: Embase, PubMed, Web of Science, SinoMed, and the Cochrane Database of Randomized Controlled Trials. The search was conducted until October 6, 2023. The primary outcomes were the pre- and post-intervention depression and anxiety scores. Secondary outcomes included dropout rates, response rates, and certain levels of neurotransmitters [ 5-hydroxytryptamine (5-HT), dopamine (DA), and gamma-aminobutyric acid (GABA)] at the end of the intervention. Subgroup, meta-regression, and sensitivity analyses were performed to explore the sources of heterogeneity. The data were analysed using R 4.2.2.

RESULTS

We included 18 RCTs [1357 participants; 11 studies used repetitive transcranial magnetic stimulation (rTMS) and 7 studies used transcranial direct current stimulation (tDCS)]. The follow-up duration varied from two weeks to three months. Overall, whether in combination with rTMS or tDCS, antidepressants proved more effective in alleviating depressive symptoms compared to when used as monotherapy. However, this advantage was not evident during the follow-up period. (p > 0.05). And the combination's efficacy in improving anxiety was found to be lacking. Post-treatment serum levels of 5-HT, DA, and GABA were higher in the rTMS group were higher than antidepressant medication group (p < 0.05). Furthermore, subgroup analysis results indicated that only the rTMS + antidepressant medication treatment significantly improved remission and remission rates. The meta-regression results showed that the type of antidepressant and the sex of the participants had a significant association with the depression score.

CONCLUSION

Combination treatment with NIBS was significantly more effective in improving depression symptoms than medication alone. rTMS combined with antidepressants appears to be more effective in improving response and remission rates. However, efficacy may be influenced by the type of medicine used in combination, and long-term efficacy data is lacking.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42023388259.

Treating depression at home with transcranial direct current stimulation: a feasibility study

Introduction

Treating major depressive disorder (MDD) with transcranial direct current stimulation (tDCS) devices at home has various logistic advantages compared to tDCS treatment in the clinic. However, preliminary (controlled) studies showed side effects such as skin lesions and difficulties in the implementation of home-based tDCS. Thus, more data are needed regarding the feasibility and possible disadvantages of home-based tDCS.

Methods

Ten outpatients (23-69 years) with an acute depressive episode were included for this one-arm feasibility study testing home-based tDCS. All patients self-administered prefrontal tDCS (2 mA, 20 min, anodal left, cathodal right) at home on 30 consecutive working days supported by video consultations. Correct implementation of the home-based treatment was analyzed with tDCS recordings. Feasibility was examined by treatment compliance. For additional analyses of effectiveness, three depression scores were used: Hamilton depression rating scale (HDRS-21), Major Depression Inventory (MDI), and the subscale depression of the Depression-Anxiety-Stress Scale (DASS). Furthermore, usability was measured with the user experience questionnaire (UEQ). Tolerability was analyzed by the number of reported adverse events (AEs).

Results

Eight patients did not stick to the protocol. AEs were minimal. Four patients responded to the home treatment according to the MDI. Usability was judged positive by the patients.

Conclusions

Regular video consultations or other safety concepts are recommended regardless of the number of video sessions actually conducted. Home-based tDCS seems to be safe and handy in our feasibility study, warranting further investigation.

Comparable Efficacy of Repeated Transcranial Direct Current Stimulation, Cognitive Behavioral Therapy, and Their Combination in Improvement of Cold and Hot Cognitive Functions and Amelioration of Depressive Symptoms

ABSTRACT

This study aimed to evaluate the effectiveness of repeated transcranial direct current stimulation (rtDCS), cognitive behavioral therapy (CBT), and their combination (rtDCS-CBT) in the treatment of cognitive dysfunction, social cognition, and depressive symptoms in women diagnosed with major depressive disorder (MDD). A total of 40 female participants with MDD were randomly assigned to one of four groups: rtDCS, CBT, rtDCS-CBT, and a control group. The participants' depressive symptoms, executive functions, and social cognition were assessed at baseline, preintervention, postintervention, and during a 1-month follow-up. The rtDCS group received 10 sessions of anodal dorsolateral and cathodal ventromedial prefrontal cortex (2 mA for 20 minutes). The CBT group received 10 sessions of traditional CBT, whereas the combined group received CBT after the tDCS sessions. The results of the analysis of variance indicated that all intervention groups demonstrated significant improvements in depressive symptoms, cognitive dysfunction, and social cognition compared with the control group (all p < 0.001). Furthermore, the rtDCS-CBT group exhibited significantly greater reductions in depressive symptoms when compared with each intervention alone (all p < 0.001). Notably, working memory improvements were observed only in the rtDCS group ( p < 0.001). In conclusion, this study suggests that both CBT and tDCS, either individually or in combination, have a positive therapeutic impact on enhancing executive functions, theory of mind, and depressive symptoms in women with MDD.

ENHANCE proof-of-concept three-arm randomized trial: effects of reaching training of the hemiparetic upper limb restricted to the spasticity-free elbow range

Post-stroke motor recovery processes remain unknown. Timescales and patterns of upper-limb (UL) recovery suggest a major impact of biological factors, with modest contributions from rehabilitation. We assessed a novel impairment-based training motivated by motor control theory where reaching occurs within the spasticity-free elbow range. Patients with subacute stroke (≤ 6 month; n = 46) and elbow flexor spasticity were randomly allocated to a 10-day UL training protocol, either personalized by restricting reaching to the spasticity-free elbow range defined by the tonic stretch reflex threshold (TSRT) or non-personalized (non-restricted) and with/without anodal transcranial direct current stimulation. Outcomes assessed before, after, and 1 month post-intervention were elbow flexor TSRT angle and reach-to-grasp arm kinematics (primary) and stretch reflex velocity sensitivity, clinical impairment, and activity (secondary). Results were analyzed for 3 groups as well as those of the effects of impairment-based training. Clinical measures improved in both groups. Spasticity-free range training resulted in faster and smoother reaches, smaller (i.e., better) arm-plane path length, and closer-to-normal shoulder/elbow movement patterns. Non-personalized training improved clinical scores without improving arm kinematics, suggesting that clinical measures do not account for movement quality. Impairment-based training within a spasticity-free elbow range is promising since it may improve clinical scores together with arm movement quality.Clinical Trial Registration: URL: http://www.clinicaltrials.gov . Unique Identifier: NCT02725853; Initial registration date: 01/04/2016.

Effects of transcranial direct current stimulation and transcranial random noise stimulation on working memory and task-related EEG in major depressive disorder

OBJECTIVE

To compare effects of transcranial direct current stimulation (tDCS) and transcranial random noise stimulation with a direct-current offset (tRNS + DC-offset) on working memory (WM) performance and task-related electroencephalography (EEG) in individuals with Major Depressive Disorder (MDD).

METHODS

Using a sham-controlled, parallel-groups design, 49 participants with MDD received either anodal tDCS (N = 16), high-frequency tRNS + DC-offset (N = 16), or sham stimulation (N = 17) to the left dorsolateral prefrontal cortex (DLPFC) for 20-minutes. The Sternberg WM task was completed with concurrent EEG recording before and at 5- and 25-minutes post-stimulation. Event-related synchronisation/desynchronisation (ERS/ERD) was calculated for theta, upper alpha, and gamma oscillations during WM encoding and maintenance.

RESULTS

tDCS significantly increased parieto-occipital upper alpha ERS/ERD during WM maintenance, observed on EEG recorded 5- and 25-minutes post-stimulation. tRNS + DC-offset did not significantly alter WM-related oscillatory activity when compared to sham stimulation. Neither tDCS nor tRNS + DC-offset improved WM performance to a significantly greater degree than sham stimulation.

CONCLUSIONS

Although tDCS induced persistent effects on WM-related oscillatory activity, neither tDCS nor tRNS + DC-offset enhanced WM performance in MDD.

SIGNIFICANCE

This reflects the first sham-controlled comparison of tDCS and tRNS + DC-offset in MDD. These findings directly contrast with evidence of tRNS-induced enhancements in WM in healthy individuals.

Home-administered transcranial direct current stimulation with asynchronous remote supervision in the treatment of depression: feasibility, tolerability, and clinical effectiveness

Introduction Background

Depression is an often chronic condition, characterized by wide-ranging physical, cognitive and psychosocial symptoms that can lead to disability, premature mortality or suicide. It affects 350 million people globally, yet up to 30% do not respond to traditional treatment, creating an urgent need for novel non-pharmacological treatments. This open-label naturalistic study assesses the practical feasibility, tolerability, and clinical effectiveness of home-administered transcranial direct current stimulation (tDCS) with asynchronous remote supervision, in the treatment of depression.

Method

Over the course of 3 weeks, 40 patients with depression received psychotherapy and half of this group also received daily bi-frontal tDCS stimulation of the dorsolateral prefrontal cortex. These patients received tDCS for 30 min per session with the anode placed over F3 and the cathode over F4, at an intensity of 2 mA for 21 consecutive days. We measured patients' level of depression symptoms at four time points using the Beck Depression Inventory, before treatment and at 1-week intervals throughout the treatment period. We monitored practical feasibility such as daily protocol compliance and tolerability including side effects, with the PlatoScience cloud-based remote supervision platform.

Results

Of the 20 patients in the tDCS group, 90% were able to comply with the protocol by not missing more than three of their assigned sessions, and none dropped out of the study. No serious adverse events were reported, with only 14 instances of mild to moderate side effects and two instances of scalp pain rated as severe, out of a total of 420 stimulation sessions. Patients in the tDCS group showed a significantly greater reduction in depression symptoms after 3 weeks of treatment, compared to the treatment as usual (TAU) group [t(57.2) = 2.268, p = 0.027]. The tDCS group also showed greater treatment response (50%) and depression remission rates (75%) compared to the TAU group (5 and 30%, respectively).

Discussion Conclusion

These findings provide a possible indication of the clinical effectiveness of home-administered tDCS for the treatment of depression, and its feasibility and tolerability in combination with asynchronous supervision.

Methylphenidate is more effective to improve inhibitory control and working memory compared to tDCS in children and adolescents with attention deficit/hyperactivity disorder: a proof-of-concept study

Introduction

Attention-deficit/hyperactivity disorder (ADHD) is characterized by an inappropriate, pervasive and persistent pattern of inattention, hyperactivity, and/or impulsivity and associated with substantial functional impairment. Despite considerable advances in the understanding and management of ADHD, some patients do not respond well to methylphenidate (MPH), the first-choice pharmacological treatment. Over the past decades, among non-invasive brain stimulation techniques, transcranial direct current stimulation (tDCS) has proven to be an effective and safe technique to improve behavior and cognition in children with neurodevelopmental disorders, including ADHD, by modifying cortical excitability. However, the effect of tDCS has never been directly compared with that of the MPH. The present randomized sham-controlled trial evaluated the effect of a single session of anodal tDCS compared with the administration of a single dose of MPH in children and adolescents with ADHD.

Methods

After completing baseline assessment (T0), 26 children and adolescents with ADHD were exposed to 3 conditions with a 24-h interval-sessions: (A) a single session of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC); (B) a single session of sham tDCS over the left DLPFC; (C) a single dose of MPH.

Results

Our results showed that after administering a single dose of MPH, children and adolescents with ADHD improved inhibitory control and visual-spatial WM compared with baseline, anodal, and sham tDCS. However, a single session of active tDCS over the left DLPFC was not effective compared with either baseline or sham tDCS.

Discussion

In conclusion, our protocol in ADHD involving a single tDCS session did not demonstrate consistent improvements in neurocognitive features compared with baseline, sham tDCS, or single MPH administration. Different protocols need to be developed to further test the effectiveness of tDCS in improving ADHD symptoms.

Effect of citicoline and transcranial direct current stimulation on depressive-like behaviors in mice & quot

Recent investigations revealed the positive role of transcranial direct current stimulation (tDCS) in the treatment of depressive-like behavior & quot. Citicoline is a dietary supplement. It acts as a neuroprotective factor for the treatment of neurological disorders. The aim of this research was to evaluate a possible interaction between tDCS and citicoline on the modulation of depressive-like behavior s & quot in male mice. For tDCS, an electrode was surgically implanted in the left prefrontal of the brain of male mice & quot. Acute restraint stress was induced by movement restraint for 4h. Locomotor activity and depressive-like behaviors & quot were examined by open field test (OFT), forced swimming test (FST), and tail suspension test (TST). The results indicated that the intraperitoneal (i.p.) administration of citicoline, left prefrontal anodal tDCS, and co-treatment of citicoline and tDCS had no significant effect on locomotor activity. I.p. injection of citicoline (30mg/kg) decreased immobility time in the FST and TST, showing an antidepressant-like effect & quot. Moreover, the application of left prefrontal anodal tDCS (0.2mA) for 20min induced antidepressant-like effect & quot by reducing immobility time in the FST and TST. Co-administration of citicoline (7 and 15mg/kg) along with tDCS (0.1mA) decreased immobility time in the FST and TST, indicating an antidepressant-like effect & quot. Therefore, it can be concluded that administration of citicoline in combination with tDCS enhanced the efficacy of tDCS for remedy of depressive-like behaviors & quot.

Time-course of the tDCS antidepressant effect: An individual participant data meta-analysis

INTRODUCTION

Prefrontal transcranial direct current stimulation (tDCS) shows promise as an effective treatment for depression. However, factors influencing treatment and the time-course of symptom improvements remain to be elucidated.

METHODS

Individual participant data was collected from ten randomised controlled trials of tDCS in depression. Depressive symptom scores were converted to a common scale, and a linear mixed effects individual growth curve model was fit to the data using k-fold cross-validation to prevent overfitting.

RESULTS

Data from 576 participants were analysed (tDCS: n = 311; sham: n = 265), of which 468 were unipolar and 108 had bipolar disorder. tDCS effect sizes reached a peak at approximately 6 weeks, and continued to diverge from sham up to 10 weeks. Significant predictors associated with worse response included higher baseline depression severity, treatment resistance, and those associated with better response included bipolar disorder and anxiety disorder.

CONCLUSIONS

Our findings suggest that longer treatment courses, lasting at least 6 weeks in duration, may be indicated. Further, our results show that tDCS is effective for depressive symptoms in bipolar disorder. Compared to unipolar depression, participants with bipolar disorder may require additional maintenance sessions to prevent rapid relapse.

Transcranial direct current stimulation for bipolar depression: systematic reviews of clinical evidence and biological underpinnings

Despite multiple available treatments for bipolar depression (BD), many patients face sub-optimal responses. Transcranial direct current stimulation (tDCS) has been advocated in the management of different conditions, including BD, especially in treatment-resistant cases. The optimal dose and timing of tDCS, the mutual influence with other concurrently administered interventions, long-term efficacy, overall safety, and biological underpinnings nonetheless deserve additional assessment. The present study appraised the existing clinical evidence about tDCS for bipolar depression, delving into the putative biological underpinnings with a special emphasis on cellular and molecular levels, with the ultimate goal of providing a translational perspective on the matter. Two separate systematic reviews across the PubMed database since inception up to August 8^th 2022 were performed, with fourteen clinical and nineteen neurobiological eligible studies. The included clinical studies encompass 207 bipolar depression patients overall and consistently document the efficacy of tDCS, with a reduction in depression scores after treatment ranging from 18% to 92%. The RCT with the largest sample clearly showed a significant superiority of active stimulation over sham. Mild-to-moderate and transient adverse effects are attributed to tDCS across these studies. The review of neurobiological literature indicates that several molecular mechanisms may account for the antidepressant effect of tDCS in BD patients, including the action on calcium homeostasis in glial cells, the enhancement of LTP, the regulation of neurotrophic factors and inflammatory mediators, and the modulation of the expression of plasticity-related genes. To the best of our knowledge, this is the first study on the matter to concurrently provide a synthesis of the clinical evidence and an in-depth appraisal of the putative biological underpinnings, providing consistent support for the efficacy, safety, and tolerability of tDCS.

Identifying factors influencing cognitive outcomes after anodal transcranial direct current stimulation in older adults with and without cognitive impairment: A systematic review

Anodal transcranial direct current stimulation (tDCS) can improve cognition in healthy older adults, those with Alzheimer's disease (AD) and mild cognitive impairment (MCI), albeit with considerable variability in response. This systematic review identifies interindividual factors that may influence tDCS outcomes in older individuals with or without cognitive impairment. Peer-reviewed articles were included if they assessed whether cognitive outcomes (memory or global cognition) after tDCS were associated with pre-intervention factors in healthy older adults or individuals with AD/MCI. We identified eight factors that may affect cognitive outcomes after tDCS. Improved tDCS outcomes were predicted by lower baseline cognitive function when tDCS was combined with a co-intervention (but not when used alone). Preserved brain structure and better baseline functional connectivity, genetic polymorphisms, and the use of concomitant medications may predict better tDCS outcomes, but further research is warranted. tDCS outcomes were not consistently associated with age, cognitive reserve, sex, and AD risk factors. Accounting for individual differences in baseline cognition, particularly for combined interventions, may thus maximize the therapeutic potential of tDCS.

Effect of high-definition transcranial direct current stimulation on improving depression and modulating functional activity in emotion-related cortical-subcortical regions in bipolar depression

Preliminary studies have suggested that transcranial direct current stimulation (tDCS) is effective for bipolar depression, However, brain correlates of the depression alleviating are unclear. To determine the efficacy and safety of tDCS as an add-on treatment for patients with bipolar depression and further to identify the effect of tDCS on the resting-state brain activities, we recruited fifty patients with bipolar depression to complete the double-blind, sham-controlled and randomized clinical trial. Fourteen sessions of tDCS were performed once a day for 14 days. The anode was placed over F3 with return electrodes placed at FP1, FZ, C3 and F7. Regional homogeneity (ReHo) was examined on 50 patients with bipolar depression before and after 14-day active or sham tDCS. Patients in the active group showed significantly superior alleviating the depression symptoms compared with those receiving sham. The active group after 14-day active tDCS showed increased ReHo values in the orbitofrontal cortex and middle frontal gyrus and decreased ReHo values in subcortical structures including hippocampus, parahippocampa gyrus, amygdala, putamen and lentiform nucleus. The reduction of depression severity showed positive correlation of increased ReHo values in the orbitofrontal cortex and middle frontal gyrus and negative correlation of altered ReHo values in the putamen and lentiform. TDCS was an effective and safe add-on intervention for this small bipolar depression sample. The reduction of depression induced by tDCS is associated with a modulation of neural synchronization in the cortical and subcortical structures (ReHo values) within an emotion-related brain network.

Can brain stimulation enhance cognition in clinical populations? A critical review

Many psychiatric and neurological conditions are associated with cognitive impairment for which there are very limited treatment options. Brain stimulation methodologies show promise as novel therapeutics and have cognitive effects. Electroconvulsive therapy (ECT), known more for its related transient adverse cognitive effects, can produce significant cognitive improvement in the weeks following acute treatment. Transcranial magnetic stimulation (TMS) is increasingly used as a treatment for major depression and has acute cognitive effects. Emerging research from controlled studies suggests that repeated TMS treatments may additionally have cognitive benefit. ECT and TMS treatment cause neurotrophic changes, although whether these are associated with cognitive effects remains unclear. Transcranial electrical stimulation methods including transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) are in development as novel treatments for multiple psychiatric conditions. These treatments may also produce cognitive enhancement particularly when stimulation occurs concurrently with a cognitive task. This review summarizes the current clinical evidence for these brain stimulation treatments as therapeutics for enhancing cognition. Acute, or short-lasting, effects as well as longer-term effects from repeated treatments are reviewed, together with potential putative neural mechanisms. Areas of future research are highlighted to assist with optimization of these approaches for enhancing cognition.

Limited time-specific and longitudinal effects of depressive and manic symptoms on cognition in bipolar spectrum disorders

OBJECTIVES

Previous research suggests that cognitive performance worsens during manic and depressed states in bipolar disorder (BD). However, studies have often relied upon between-subject, cross-sectional analyses and smaller sample sizes. The current study examined the relationship between mood symptoms and cognition in a within-subject, longitudinal study with a large sample.

METHODS

Seven hundred and seventy-three individuals with BD completed a neuropsychological battery and mood assessments at baseline and 1-year follow-up. The battery captured eight domains of cognition: fine motor dexterity, visual memory, auditory memory, emotion processing, and four aspects of executive functioning: verbal fluency and processing speed; conceptual reasoning and set shifting; processing speed with influence resolution; and inhibitory control. Structural equation modeling was conducted to examine the cross-sectional and longitudinal relationships between depressive symptoms, manic symptoms, and cognitive performance. Age and education were included as covariates. Eight models were run with the respective cognitive domains.

RESULTS

Baseline mood positively predicted 1-year mood, and baseline cognition positively predicted 1-year cognition. Mood and cognition were generally not related for the eight cognitive domains. Baseline mania was predictive in one of eight baseline domains (conceptual reasoning and set shifting); baseline cognition predicted 1-year symptoms (inhibitory control-depression symptoms, visual memory-manic symptoms).

CONCLUSIONS

In a large community sample of patients with bipolar spectrum disorder, cognitive performance appears to be largely unrelated to depressive and manic symptoms, suggesting that cognitive dysfunction is stable in BD and is not dependent on mood state in BD. Future work could examine how treatment affects relationship between cognition and mood.

SIGNIFICANT OUTCOMES

Cognitive dysfunction appears to be largely independent of mood symptoms in bipolar disorder.

LIMITATIONS

The sample was generally highly educated (M = 15.22), the majority of the subsample with elevated manic symptoms generally presented with concurrent depressive elevated symptoms, and the study did not stratify recruitment based on mood state.

Efficacy and safety of daily home-based transcranial direct current stimulation as adjunct treatment for bipolar depressive episodes: Double-blind sham-controlled randomized clinical trial

Background

Although transcranial direct current stimulation (tDCS) is known to be a promising therapeutic modality for unipolar depression, the efficacy and safety of tDCS for bipolar depressive episodes (BD) are still unknown and clinical trials of home-based tDCS treatment are scarce. As a result, we set out to investigate the efficacy and safety of home-based tDCS for the treatment BD.

Methods

Participants (n = 64), diagnosed as bipolar disorder as per the diagnostic and statistical manual of mental disorders (DSM-5), were randomly assigned to receive tDCS. Hamilton Depression Rating Scale (HDRS-17) scores were measured at the baseline, week 2, 4, and 6, and home-based tDCS (for 30 min with 2 mA) was self-administered daily.

Results

Of the 64 patients (15.6% bipolar disorder I, 84.4% bipolar disorder II), 41 patients completed the entire assessment. In the intention-to-treat analysis, time-group interaction for the HDRS-17 [F (3, 146.36) = 2.060; p = 0.108] and adverse effect differences between two groups were not statistically significant, except the pain score, which was higher in the active group than the sham group (week 0-2: p < 0.01, week 2-4: p < 0.05, and week 4-6: p < 0.01).

Conclusion

Even though we found no evidence for the efficacy of home-based tDCS for patients with BD, this tool was found to be a safe and tolerable treatment modality for BD.

Clinical trial registration

[https://clinicaltrials.gov/show/NCT03974815], identifier [NCT03974815].

Non-invasive neuromodulation of dorsolateral prefrontal cortex to reduce craving in alcohol use disorder: A meta-analysis

Introduction

While several pharmacological and behavioral treatments are available for alcohol use disorder (AUD), they may not be effective for all patients. The aim of this systematic review and meta-analysis was to evaluate the efficacy and safety of rTMS and tDCS for craving in AUD.

Methods

EMBASE, Cochrane Library, PsycINFO, and PubMed databases were searched for original, peer-reviewed research articles in the English language published between January 2000 and January 2022. Randomized controlled trials (RCTs) reporting changes in alcohol craving among patients with AUD were selected. Random-effects meta-analysis was employed to pool data.

Results

Changes in alcohol craving were extracted from 15 RCTs. Six studies assessed the efficacy of rTMS while nine studies examined tDCS. Results demonstrated that in comparison to sham stimulation, active rTMS to the DLPFC yields small but significant reductions in alcohol craving (standardized mean difference [SMD] = -0.27, p = .03). However, DLPFC stimulation via tDCS was not superior to sham stimulation in producing changes in alcohol craving (SMD = -0.08, p = .59).

Conclusions

Our meta-analysis suggests that rTMS may be superior to tDCS in reducing alcohol craving in patients with AUD. However, additional research is needed to identify optimal stimulation parameters for both non-invasive neuromodulatory techniques in AUD.

Noninvasive Brain Stimulation Therapies to Promote Recovery of Consciousness: Where We Are and Where We Should Go

Therapeutic options for patients with disorders of consciousness (DoC) are still underexplored. Noninvasive brain stimulation (NIBS) techniques modulate neural activity of targeted brain areas and hold promise for the treatment of patients with DoC. In this review, we provide a summary of published research using NIBS as therapeutic intervention for DoC patients, with a focus on (but not limited to) randomized controlled trials (RCT). We aim to identify current challenges and knowledge gaps specific to NIBS research in DoC. Furthermore, we propose possible solutions and perspectives for this field. Thus far, the most studied technique remains transcranial electrical stimulation; however, its effect remains moderate. The identified key points that NIBS researchers should focus on in future studies are (1) the lack of large-scale RCTs; (2) the importance of identifying the endotypes of responders; and (3) the optimization of stimulation parameters to maximize the benefits of NIBS.

Transcranial Direct Current Stimulation of the Dorsolateral Prefrontal Cortex for Treatment of Neuropsychiatric Disorders

Background

The dorsolateral prefrontal cortex (DLPFC) is a key node of the frontal cognitive circuit. It is involved in executive control and many cognitive processes. Abnormal activities of DLPFC are likely associated with many psychiatric diseases. Modulation of DLPFC may have potential beneficial effects in many neural and psychiatric diseases. One of the widely used non-invasive neuromodulation technique is called transcranial direct current stimulation (or tDCS), which is a portable and affordable brain stimulation approach that uses direct electrical currents to modulate brain functions.

Objective

This review aims to discuss the results from the past two decades which have shown that tDCS can relieve clinical symptoms in various neurological and psychiatric diseases.

Methods

Here, we performed searches on PubMed to collect clinical and preclinical studies that using tDCS as neuromodulation technique, DLPFC as the stimulation target in treating neuropsychiatric disorders. We summarized the stimulation sites, stimulation parameters, and the overall effects in these studies.

Results

Overall, tDCS stimulation of DLPFC could alleviate the clinical symptoms of schizophrenia, depression, drug addiction, attention deficit hyperactivity disorder and other mental disorders.

Conclusion

The stimulation parameters used in these studies were different from each other. The lasting effect of stimulation was also not consistent. Nevertheless, DLPFC is a promising target for non-invasive stimulation in many psychiatric disorders. TDCS is a safe and affordable neuromodulation approach that has potential clinical uses. Larger clinical studies will be needed to determine the optimal stimulation parameters in each condition.

A Randomized, Double-Blind, Sham-Controlled Trial of Transcranial Direct Current Stimulation for the Treatment of Persistent Postural-Perceptual Dizziness (PPPD)

Background

Persistent postural-perceptual dizziness (PPPD) is a functional vestibular disorder that causes chronic dizziness interfering with daily activities. Transcranial direct current stimulation (tDCS) has reportedly improved dizziness in patients with phobic postural vertigo in an open-label trial. However, no randomized, double-blind, sham-controlled study has been conducted on its therapeutic efficacy in PPPD.

Objective

This study was conducted to investigate the efficacy and safety of tDCS as an add-on treatment to pharmacotherapy in patients with PPPD. In addition, functional neuroimaging was used to identify the neural mechanisms underlying the effects of tDCS.

Materials and Methods

In a randomized, double-blind, sham-controlled trial, 24 patients diagnosed with PPPD were randomized to receive active (2 mA, 20 min) or sham tDCS to the left dorsolateral prefrontal cortex (DLPFC), administered in 15 sessions over 3 weeks. The clinical measures that assess the severity of dizziness, depression, and anxiety were collected at baseline, immediate follow-up, 1-month follow-up, and 3-month follow-up. Adverse events were also observed. The effect of tDCS on regional cerebral blood flow (rCBF) was evaluated with single photon emission tomography before and after tDCS sessions.

Results

For the primary outcome measure of the Dizziness Handicap Inventory (DHI) score, a significant main effect of time was found, but neither the treatment-by-time interaction effect nor the main effect of treatment was significant. For the Hamilton Depression Rating Scale (HDRS) score, there was a statistical significance for the treatment-by-time interaction effect and the main effect of time, but not for the main effect of treatment. However, the treatment-by-time interaction effect and the main effect of time on HDRS score appear to be due to one data point, an increase in depressive symptoms reported by the sham group at the 3-month follow-up. For the Activities-specific Balance Confidence (ABC) Scale and the Hamilton Anxiety Rating Scale scores, there were no significant main effects of time, treatment, and treatment-by-time interaction. In a comparison with the changes in rCBF between the groups, a significant treatment-by-time interaction effect was found in the right superior temporal and left hippocampus, controlling for age and sex.

Conclusion

Active tDCS was not found to be significantly more efficacious than sham tDCS on dizziness symptoms in patients with PPPD. It is conceivable that tDCS targeting the DLPFC may not be an optimal treatment option for reducing dizziness symptoms in PPPD. Our findings encourage further investigation on the effects of tDCS in PPPD, which considers different stimulation protocols in terms of stimulation site or the number of sessions.

Clinical Trial Registration

cris.nih.go.kr, identifier: KCT0005068.

Home-based transcranial direct current stimulation in dual active treatments for symptoms of depression and anxiety: A case series

Transcranial direct current stimulation (tDCS) is a potential treatment strategy across some psychiatric conditions. However, there is high heterogeneity in tDCS efficacy as a stand-alone treatment. To increase its therapeutic potential, researchers have begun to explore the efficacy of combining tDCS with psychological and pharmacological interventions. The current case series details the effect of 6-10 weeks of self-administered tDCS paired with a behavioral therapy smartphone app (Flow™), on depressive and anxiety symptoms, in seven patients (26-51 years old; four female) presenting distinctive psychiatric disorders (major depression, dysthymia, illness anxiety disorder, obsessive-compulsive disorder, and anxiety disorders). tDCS protocol consisted of an acute phase of daily 30 min sessions, across 10 workdays (2 weeks Monday-to-Friday; Protocol 1) or 15 workdays (3 weeks Monday-to-Friday; Protocol 2). A maintenance phase followed, with twice-weekly sessions for 4 or 3 weeks, corresponding to 18 or 21 sessions in total (Protocol 1 or 2, respectively). The Flow tDCS device uses a 2 mA current intensity, targeting the bilateral dorsolateral prefrontal cortex. The Flow app offers virtually guided behavioral therapy courses to be completed during stimulation. We assessed depressive symptoms using MADRS-S and BDI-II, anxious symptoms using STAI-Trait, acceptability using ACCEPT-tDCS, and side effects using the Adverse Effects Questionnaire, at baseline and week 6 of treatment. Six patients underwent simultaneous cognitive-behavioral psychotherapy and two were on antidepressants and benzodiazepines. According to the Reliable Change Index (RCI), for depressive symptoms, we found clinically reliable improvement in five patients using MADRS-S (out of seven; RCI: -1.45, 80% CI; RCI: -2.17 to -4.82, 95% CI; percentage change: 37.9-66.7%) and in four patients using BDI-II (out of five; RCI: -3.61 to -6.70, 95% CI; percentage change: 57.1-100%). For anxiety symptoms, clinically reliable improvement was observed in five patients (out of six; RCI: -1.79, 90% CI; RCI: -2.55 to -8.64, 95% CI; percentage change: 12.3-46.4%). Stimulation was well-tolerated and accepted, with mild tingling sensation and scalp discomfort being the most common side effects. This case series highlights the applicability, acceptability, and promising results when combining home-based tDCS with psychotherapy and pharmacotherapy to manage depression and anxiety symptoms in clinical practice.

Cerebellar Transcranial Direct Current Stimulation in Children with Autism Spectrum Disorder: A Pilot Study on Efficacy, Feasibility, Safety, and Unexpected Outcomes in Tic Disorder and Epilepsy

Patients with autism spectrum disorder (ASD) display distinctive neurophysiological characteristics associated with significant cognitive, emotional, and behavioral symptoms. Transcranial direct current stimulation (tDCS) applied to the frontal or temporoparietal lobes has demonstrated potential to reduce the severity of ASD-related symptoms. Recently, the cerebellum has been identified as a brain area involved in ASD pathophysiology. In this open-label pilot study, seven ASD patients aged between 9 and 13 years underwent 20 daily sessions of 20 min cathodal stimulation of the right cerebellar lobe. At the end of the treatment, the Aberrant Behavior Checklist (ABC) scores showed a 25% mean reduction in global severity of symptoms, with a more pronounced reduction in the “social withdrawal and lethargy” (−35%), “hyperactivity and noncompliance” (−26%), and “irritability, agitation, and crying” (−25%) subscales. Minor and no improvement were observed in the “stereotypic behavior” (−18%) and “inappropriate speech” (−0%) subscales, respectively. Improvements were not detected in the two patients who were taking psychotropic drugs during the study. Clinical response showed a symptom-specific time course. Quality of sleep and mood improved earlier than hyperactivity and social withdrawal. The treatment was generally accepted by patients and well tolerated. No serious adverse events were reported. Stimulation also appeared to markedly reduce the severity of tics in a patient with comorbid tic disorder and led to the disappearance of a frontal epileptogenic focus in another patient with a history of seizures. In conclusion, cerebellar tDCS is safe, feasible, and potentially effective in the treatment of ASD symptoms among children. Strategies to improve recruitment and retention are discussed.

Is transcranial direct current stimulation, alone or in combination with antidepressant medications or psychotherapies, effective in treating major depressive disorder? A systematic review and meta-analysis

BACKGROUND

Transcranial direct current stimulation (tDCS) has shown mixed results for depression treatment. The efficacies of tDCS combination therapies have not been investigated deliberately. This review aims to evaluate the clinical efficacy of tDCS as a monotherapy and in combination with medication, psychotherapy, and ECT for treating adult patients with major depressive disorder (MDD) and identified the factors influencing treatment outcome measures (i.e. depression score, dropout, response, and remission rates).

METHODS

The systematic review was performed in PubMed/Medline, EMBASE, PsycINFO, Web of Sciences, and OpenGrey. Two authors performed independent literature screening and data extraction. The primary outcomes were the standardized mean difference (SMD) for continuous depression scores after treatment and odds ratio (OR) dropout rate; secondary outcomes included ORs for response and remission rates. Random effects models with 95% confidence intervals were employed in all outcomes. The overall effect of tDCS was investigated by meta-analysis. Sources of heterogeneity were explored via subgroup analyses, meta-regression, sensitivity analyses, and assessment of publication bias.

RESULTS

Twelve randomised, sham-controlled trials (active group: N = 251, sham group: N = 204) were included. Overall, the integrated depression score of the active group after treatment was significantly lower than that of the sham group (g = - 0.442, p = 0.017), and further analysis showed that only tDCS + medication achieved a significant lower score (g = - 0.855, p < 0.001). Moreover, this combination achieved a significantly higher response rate than sham intervention (OR = 2.7, p = 0.006), while the response rate remained unchanged for the other three therapies. Dropout and remission rates were similar in the active and sham groups for each therapy and also for the overall intervention. The meta-regression results showed that current intensity is the only predictor for the response rate. None of publication bias was identified.

CONCLUSION

The effect size of tDCS treatment was obviously larger in depression score compared with sham stimulation. The tDCS combined selective serotonin re-uptake inhibitors is the optimized therapy that is effective on depression score and response rate. tDCS monotherapy and combined psychotherapy have no significant effects. The most important parameter for optimization in future trials is treatment strategy.

Neuroprotection by Transcranial Direct Current Stimulation in Rodent Models of Focal Ischemic Stroke: A Meta-Analysis

Infarct size is associated with stroke severity in clinical studies, so reducing it has become an important target and research hotspot in the treatment of ischemic stroke. Some preclinical studies have shown transcranial direct current stimulation (tDCS) reduced infarct size and improved neurological deficit, but others have not found beneficial effects. Besides, the optimal pattern of tDCS for ischemic stroke remains largely unknown. To shed light on the current circumstance and future research directions, the systematic review evaluated the effect of different tDCS paradigms in reducing infarct size and improving neurological deficit in rodent models of ischemic stroke and assessed the methodological quality of current literature. We searched the MEDLINE (via PubMed), EMBASE, Web of Science, and Scopus from their inception to August 18, 2021, to identify studies evaluating the effects of tDCS in rodent models of ischemic stroke. Eight studies were included, of which seven studies were included in the meta-analysis. The results showed cathodal tDCS, rather than anodal tDCS, reduced infarct size mainly measured by tetrazolium chloride and magnetic resonance imaging (standardized mean difference: -1.13; 95% CI: -1.72, -0.53; p = 0.0002) and improved neurological deficit assessed by a modified neurological severity score (standardized mean difference: -2.10; 95% CI: -3.78, -0.42; p = 0.01) in an early stage of focal ischemic stroke in rodent models. Subgroup analyses showed effects of cathodal tDCS on infarct size were not varied by ischemia duration (ischemia for 1, 1.5, and 2 h or permanent ischemia) and anesthesia (involving isoflurane and ketamine). The overall quality of studies included was low, thus the results must be interpreted cautiously. Published studies suggest that cathodal tDCS may be a promising avenue to explore for augmenting rehabilitation from focal ischemic stroke. Considering the methodological limitations, it is unreliable to blindly extrapolate the animal data to the clinical practice. Future research is needed to investigate the mechanism of tDCS in a randomized and blinded fashion in clinically relevant stroke models, such as elderly animals, female animals, and animals with comorbidities, to find an optimal treatment protocol.

Fundamentals of Neuromodulation and Pathophysiology of Neural Networks in Health and Disease

Neuromodulation involves altering neuronal circuitry and subsequent physiological changes with the aim to ameliorate neurological symptoms. Over the years several techniques have been used to obtain neuromodulatory effects for treatment of conditions including Parkinson disease, essential tremor, dystonia or seizures. We provide brief description of the various therapeutics that have been used and mechanisms involved in pathophysiology of these disorders as well as the therapeutic mechanisms of the treatment modalities.

Transcranial Direct Current Stimulation Targeting the Ventromedial Prefrontal Cortex Reduces Reactive Aggression and Modulates Electrophysiological Responses in a Forensic Population

BACKGROUND

Studies have shown that impairments in the ventromedial prefrontal cortex play a crucial role in violent behavior in forensic patients who also abuse cocaine and alcohol. Moreover, interventions that aimed to reduce violence risk in those patients are found not to be optimal. A promising intervention might be to modulate the ventromedial prefrontal cortex by high-definition (HD) transcranial direct current stimulation (tDCS). The current study aimed to examine HD-tDCS as an intervention to increase empathic abilities and reduce violent behavior in forensic substance dependent offenders. In addition, using electroencephalography, we examined the effects on the P3 and the late positive potential of the event-related potentials in reaction to situations that depict victims of aggression.

METHODS

Fifty male forensic patients with a substance dependence were tested in a double-blind, placebo-controlled randomized study. The patients received HD-tDCS 2 times a day for 20 minutes for 5 consecutive days. Before and after the intervention, the patients completed self-reports and performed the Point Subtraction Aggression Paradigm, and electroencephalography was recorded while patients performed an empathy task.

RESULTS

Results showed a decrease in aggressive responses on the Point Subtraction Aggression Paradigm and in self-reported reactive aggression in the active tDCS group. Additionally, we found a general increase in late positive potential amplitude after active tDCS. No effects on trait empathy and the P3 were found.

CONCLUSIONS

Current findings are the first to find positive effects of HD-tDCS in reducing aggression and modulating electrophysiological responses in forensic patients, showing the potential of using tDCS as an intervention to reduce aggression in forensic mental health care.

Distinct trajectories of response to prefrontal tDCS in major depression: results from a 3-arm randomized controlled trial

Transcranial direct current stimulation (tDCS) is a safe, effective treatment for major depressive disorder (MDD). While antidepressant effects are heterogeneous, no studies have investigated trajectories of tDCS response. We characterized distinct improvement trajectories and associated baseline characteristics for patients treated with prefrontal tDCS, an active pharmacotherapy (escitalopram), and placebo. This is a secondary analysis of a randomized, non-inferiority, double-blinded trial (ELECT-TDCS, N = 245). Participants were diagnosed with an acute unipolar, nonpsychotic, depressive episode, and presented Hamilton Depression Rating Scale (17-items, HAM-D) scores ≥17. Latent trajectory modeling was used to identify HAM-D response trajectories over a 10-week treatment. Top-down (hypothesis-driven) and bottom-up (data-driven) methods were employed to explore potential predictive features using, respectively, conservatively corrected regression models and a cross-validated stability ranking procedure combined with elastic net regularization. Three trajectory classes that were distinct in response speed and intensity (rapid, slow, and no/minimal improvement) were identified for escitalopram, tDCS, and placebo. Differences in response and remission rates were significant early for all groups. Depression severity, use of benzodiazepines, and age were associated with no/minimal improvement. No significant differences in trajectory assignment were found in tDCS vs. placebo comparisons (38.3, 34, and 27.6%; vs. 23.3, 43.3, and 33.3% for rapid, slow, and no/minimal trajectories, respectively). Additional features are suggested in bottom-up analyses. Summarily, groups treated with tDCS, escitalopram, and placebo differed in trajectory class distributions and baseline predictors of response. Our results might be relevant for designing further studies.

Efficacy and neurophysiological predictors of treatment response of adjunct bifrontal transcranial direct current stimulation (tDCS) in treating unipolar and bipolar depression

BACKGROUND

Although add-on transcranial direct current stimulation (tDCS) is a promising intervention for treating unipolar (UD) and bipolar depression (BD), its moderate antidepressant efficacy urges research into biomarkers for predicting therapeutic response and achieving highly targeted applications.

METHODS

This open-label trial enrolled UD (N=58) and BD (N=22) patients who had failed 1 or more trials of adequate pharmacologic interventions (ClinicalTrials.gov ID: NCT03287037). Bifrontal tDCS (anode/cathode: F3/F4) was applied using a 2 mA current for 20 min, twice daily, for 5 consecutive weekdays. Depression was measured with Hamilton Depression Rating Scale-17 (HAMD) at baseline, after 10-session stimulation, 1- and 4-week follow-ups. Heart rate (HR) and heart rate variability (HRV) was measured at baseline, during the initial 5 min of the 1^st session, after 10-session stimulation, 1- and 4-week follow-ups. Cognitive performance and other outcomes were also assessed.

RESULTS

Bifrontal tDCS rapidly and equally improved depression in both groups. The effects persisted until the end of the trial. Both groups had similar improvements in cognitive performance, anxiety, and psychosocial functioning. Compared with baseline, increased vagally-mediated HRV was observed one month after tDCS for both groups. A positive correlation was found between HR deceleration within the 1^st session and treatment response after 10-session tDCS only among UD patients, explaining 20% of the variance.

CONCLUSION

tDCS as an adjunct therapy is effective for both UD and BD. Data suggest that the greater the increase in parasympathetic signaling during the 1^st session, the better the clinical response after 10-session tDCS for UD patients.

Bifrontal high-frequency transcranial random noise stimulation is not effective as an add-on treatment in depression

BACKGROUND

Depressive disorders are linked to dysfunction in prefrontal cortical areas. Hence, non-invasive neurostimulation of the prefrontal cortex has demonstrated antidepressant efficacy. In the present study, we investigated the efficacy of high frequency transcranial random noise stimulation (hf-tRNS) as an add-on treatment for depression in a sham-controlled randomized trial.

METHODS

Forty in-patients with depression were randomized and treated with real or sham hf-tRNS (100-650 Hz) with 0 mA offset. The electrodes were mounted over the left and right dorsolateral prefrontal cortex. The Hamilton Depression Rating Scale (primary outcome), the Major Depression Inventory, the Clinical Global Impression scale and the Global Assessment of Functioning scale were used for assessment at baseline, after 3 weeks of intervention (end of treatment), and 9 weeks after intervention. Safety parameters included cognitive functioning and reported side-effects.

RESULTS

Comparison of real and sham treatment at the planned interim analysis showed an amelioration of symptoms in both groups for all outcomes with numeric but not statistically significant superiority of the sham arm for the primary outcome. Thus, the study was terminated prematurely after an interim analysis. There were no systematic differences with respect to safety parameters.

LIMITATIONS

The negative finding might be related to the specific stimulation parameters used in this study.

CONCLUSIONS

Our study suggests that prefrontal hf-tRNS is safe but not effective as an add-on treatment of depression. The challenge for future studies employing transcranial electric stimulation remains to identify effective stimulation parameters for the treatment of depression.

Influence of Transcranial Direct Current Stimulation on Psychomotor Symptoms in Major Depression

Background: Transcranial direct current stimulation (tDCS) applied to the left dorsolateral prefrontal cortex (dlPFC) might be a promising treatment strategy for depression. As disturbances in psychomotor activity are one of the key features of unipolar depression are, we aimed to evaluate the behavioral effects of ten tDCS sessions over a 5-day period on psychomotor retardation in depressed patients. Methods: Twenty-three treatment-resistant depressed patients received either active or sham anodal tDCS to the left dorsolateral prefrontal cortex (2 mA, 10 sessions over 1 week). Psychomotor functioning was registered by means of observer ratings (Salpêtrière Retardation Rating Scale—SRRS) and objective measures (kinematical analysis of movements, automatic imitation). Results: tDCS sessions resulted in improvements on SRRS scores, although active tDCS was not significantly superior to sham tDCS on the kinematical parameters. Furthermore, no general additional antidepressant effect of tDCS was observed. The relatively small sample size and the short periods of observation should be considered when interpreting these results. Conclusion: tDCS did not induce a clinically relevant effect on psychomotor function in active and sham stimulation groups.

Transcranial direct current stimulation: A novel approach in the treatment of vascular depression

BACKGROUND

Despite the impact of depression in terms of personal suffering and socioeconomic burden, most currently available treatment options are often ineffective. A particularly difficult-to-treat depressive disorder characteristic of the elderly is vascular depression, a late-life depressive syndrome related to a variety of potential vascular mechanisms. Transcranial Direct Current Stimulation (tDCS), a non-invasive and effective somatic approach to depression, also showed positive effects on cognitive deficits.

AIM

We performed a double-blind randomized study to investigate the efficacy of tDCS as augmentation strategy to sertraline in the treatment of vascular depression, hypothesizing a positive effect in both depressive symptoms and cognitive functions.

METHODS

We enrolled 93 inpatients over 60 years of age with a diagnosis of vascular depression. Depressive symptoms were weekly assessed (T0, T1, T2) with the 21-items Hamilton depression rating scale (HDRS). Cognitive functioning was evaluated with the Milan Overall Dementia Assessment (MODA) at baseline and after the treatment protocol. All patients were randomly assigned into three groups, Group I: one tDCS stimulation per day, Group II: two tDCS stimulations per day, Sham group: one sham tDCS stimulation per day. Stimulation was performed for 10 consecutive working days.

RESULTS

A significant interaction time∗treatment was observed on HDRS scores (F = 14, p < 0.001). All groups improved at T1 but whereas Group II significantly differed from the Sham group (p < 0.001) we observed no difference between Sham and Group I. At T2 all groups improved but Group II showed the greater improvement (vs. Sham p < 0.001; vs. Group I p < 0.001) and the Sham group the smallest (vs. Group I p = 0.005). A significant interaction time∗treatment was also observed on MODA scores (F = 3.31, p = 0.04). Only subjects treated with tDCS improved at T2 (Group I: p < 0.001; Group II: p = 0.007). However, no difference between Group I and II was shown.

CONCLUSION

tDCS as augmentation treatment of an adequate pharmacotherapy is a potential strategy in the management of vascular depression, a disease known to be often unresponsive to antidepressants only. Non-invasiveness, the absence of severe side effects and the possibility of administering it to outpatients at an affordable price make tDCS an important tool in clinical practice.

Understanding the effects of chronic benzodiazepine use in depression: a focus on neuropharmacology

Benzodiazepines are frequently prescribed on an ongoing basis to individuals with depression, mainly to alleviate anxiety or insomnia, despite current guideline recommendations that continuous use should not exceed 4 weeks. Currently, there are no efficacy trials published beyond 8 weeks. Several antidepressant trials demonstrate that the concomitant use of a benzodiazepine is associated with poorer depressive outcomes and functional status; however, it is unclear why this is the case. Patients with depression receiving a benzodiazepine may reflect a more ill or high anxiety group, although even within anxiety disorders, the use of a benzodiazepine is associated with poorer outcomes. The neuroadaptive consequences of long-term benzodiazepine use may be a factor underlying these findings. Chronic benzodiazepine use results in decreased gamma-aminobutyric acid and monoaminergic function, as well as interference with neurogenesis, which are all purported to play a role in antidepressant efficacy. This review will discuss the oppositional neuropharmacological interactions between chronic benzodiazepine use and antidepressant mechanism of action, which could result in reduced antidepressant efficacy and function in depression.

tDCS Accelerates the Rehabilitation of MCAO-Induced Motor Function Deficits via Neurogenesis Modulated by the Notch1 Signaling Pathway

Background. Ischemic stroke carries a high mortality rate and is a leading cause of severe neurological disability. However, the efficacy of current therapeutic options remains limited. Objective. We aimed to investigate the treatment efficacy of transcranial direct current stimulation (tDCS) in motor function rehabilitation after ischemic stroke and explore the underlying mechanisms. Methods. Male Sprague-Dawley rats with epicranial electrodes were used to establish pathogenetic model through temporary right middle cerebral artery occlusion (MCAO). Subsequently, animals were randomly divided into 4 groups: MCAO + tDCS/sham tDCS, Control + tDCS/sham tDCS. Animals in the groups with tDCS underwent 10 days of cathodal tDCS totally (500 µA, 15 minutes, once a day). During and after tDCS treatment, the motor functions of the animals, ischemic damage area, proliferation and differentiation of neural stem cells (NSCs), and distribution, and protein expression of Notch1 signaling molecules were detected. Results. The rehabilitation of MCAO-induced motor function deficits was dramatically accelerated by tDCS treatment. NSC proliferation in the subventricular zone (SVZ) was significantly increased after MCAO surgery, and tDCS treatment promoted this process. Additionally, NSCs probably migrated from the SVZ to the ischemic striatum and then differentiated into neurons and oligodendrocytes after MCAO surgery, both of which processes were accelerated by tDCS treatment. Finally, tDCS treatment inhibited the activation of Notch1 signaling in NSCs in the ischemic striatum, which may be involved in NSC differentiation in the MCAO model. Conclusion. Our results suggest that tDCS may exert therapeutic efficacy after ischemic stroke in a regenerative medical perspective.

Transcranial Random Noise Stimulation for the Acute Treatment of Depression: A Randomized Controlled Trial

BACKGROUND

Transcranial electrical stimulation has broad potential as a treatment for depression. Transcranial random noise stimulation, which delivers randomly fluctuating current intensities, may have greater cortical excitatory effects compared with other forms of transcranial electrical stimulation. We therefore aimed to investigate the antidepressant efficacy of transcranial random noise stimulation.

METHODS

Depressed participants were randomly assigned by computer number generator to receive 20 sessions of either active or sham transcranial random noise stimulation over 4 weeks in a double-blinded, parallel group randomized-controlled trial. Transcranial random noise stimulation was delivered for 30 minutes with a direct current offset of 2 mA and a random noise range of 2 mA. Primary analyses assessed changes in depression severity using the Montgomery-Asperg Depression Rating Scale. Neuroplasticity, neuropsychological, and safety outcomes were analyzed as secondary measures.

RESULTS

Sixty-nine participants were randomized, of which 3 discontinued treatment early, leaving 66 (sham n = 34, active n = 32) for per-protocol analysis. Depression severity scores reduced in both groups (Montgomery-Asperg Depression Rating Scale reduction in sham = 7.0 [95% CI = 5.0-8.9]; and active = 5.2 [95% CI = 3.2-7.3]). However, there were no differences between active and sham groups in the reduction of depressive symptoms or the number of participants meeting response (sham = 14.7%; active = 3.1%) and remission criteria (sham = 5.9%; active = 0%). Erythema, paresthesia, fatigue, and dizziness/light-headedness occurred more frequently in the active transcranial random noise stimulation group. Neuroplasticity, neuropsychological, and acute cognitive effects were comparable between groups.

CONCLUSION

Our results do not support the use of transcranial random noise stimulation with the current stimulation parameters as a therapeutic intervention for the treatment of depression.

CLINICAL TRIAL REGISTRATION AT CLINICALTRIALS

gov/NCT01792414.

Imaging Transcranial Direct Current Stimulation (tDCS) with Positron Emission Tomography (PET)

Transcranial direct current stimulation (tDCS) is a form of non-invasive neuromodulation that is increasingly being utilized to examine and modify several cognitive and motor functions. Although tDCS holds great potential, it is difficult to determine optimal treatment procedures to accommodate configurations, the complex shapes, and dramatic conductivity differences among various tissues. Furthermore, recent demonstrations showed that up to 75% of the tDCS current applied to rodents and human cadavers was shunted by the scalp, subcutaneous tissue, and muscle, bringing the effects of tDCS on the cortex into question. Consequently, it is essential to combine tDCS with human neuroimaging to complement animal and cadaver studies and clarify if and how tDCS can affect neural function. One viable approach is positron emission tomography (PET) imaging. PET has unique potential for examining the effects of tDCS within the central nervous system in vivo, including cerebral metabolism, neuroreceptor occupancy, and neurotransmitter activity/binding. The focus of this review is the emerging role of PET and potential PET radiotracers for studying tDCS-induced functional changes in the human brain.

Single-Session of Combined tDCS-TMS May Increase Therapeutic Effects in Subjects With Tinnitus

To treat motor and psychiatric disorders, transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are used in clinics worldwide. We combined these two types of neuromodulation technique to increase the effective response of a single session of neuromodulation in subjective tinnitus. Eighty tinnitus subjects were split into four different treatment groups: tDCS, tDCS with sham TMS, tDCS-TMS, and TMS group. Subjects were given 1.5 mA tDCS on the bi-frontal area and TMS stimulated the contralateral single side of the temporo-parietal cortex with 200 pulses at 1 Hz stimulation. Comparing pre-treatment questionnaire scores to post-treatment questionnaire scores, all four groups showed statistically significant improvements. Although there was no significant difference among group comparison, the largest mean difference was shown in the combined group, especially for tinnitus intensity and tinnitus-related distress. Responders in the combined group were the highest for VAS intensity, with a maximum of 80% of twenty subjects. To summarize, dual-neuromodulation responders could consist of responders of frontal tDCS and temporal TMS. In addition, abnormal activity in the frontal or temporal area of the responders is presumed to be modulated by treatment and will be suggested as the target areas in future studies.

Cost-utility analysis of transcranial direct current stimulation (tDCS) in non-treatment-resistant depression: the DISCO randomised controlled study protocol

INTRODUCTION

Depression is among the most widespread psychiatric disorders in France. Psychiatric disorders are associated with considerable social costs, amounting to €22.6 billion for treatment and psychotropic medication in 2011. Treatment as usual (TAU), mainly consisting of pharmacotherapy and psychotherapy, is effective for only a third of patients and in most cases fails to prevent treatment resistance and chronicity. Transcranial direct current stimulation (tDCS) consists in a non-invasive and painless application of low-intensity electric current to the cerebral cortex through the scalp. Having proved effective in depressed patients, it could be used in combination with TAU to great advantage. The objective is to compare, for the first time ever, the cost-utility of tDCS-TAU and of TAU alone for the treatment of a depressive episode that has been refractory to one or two drug treatments.

METHODS AND ANALYSIS

This paper, based on the DISCO study protocol, focuses on the design of a prospective, randomised, controlled, open-label multicentre economic study to be conducted in France. It will include 214 patients with unipolar or bipolar depression, assigning them to two parallel arms: group A (tDCS-TAU) and group B (TAU alone). The primary outcome is the incremental cost-effectiveness ratio, that is, the ratio of the difference in cost between each strategy to the difference in their effects. Their effects will be expressed as numbers of quality-adjusted life-years, determined through administration of the EuroQol Five-Dimension questionnaire over a 12-month period to patients (EQ-5D-5L). Expected benefits are the reduction of treatment resistance and suicidal ideation as well as social and professional costs of depression. Should depression-related costs fall significantly, tDCS might be considered an efficient treatment for depression.

ETHICS AND DISSEMINATION

This protocol has been approved by a French ethics committee, the CPP--Est IV (Comité de Protection des Personnes-Strasbourg). Data are to be published in peer-reviewed medical journals.

TRIAL REGISTRATION NUMBER

RCB 2018-A00474-51; NCT03758105.

Transcranial Direct Current Stimulation for Treatment-Resistant Major Depression: A Double-Blind Randomized Sham-Controlled Trial

In the current study, we tried to evaluate the effect of transcranial direct current stimulation (tDCS) on treatment-resistant major depression. We carried out a double-blind randomized sham-controlled trial was conducted in University Hospitals. Individuals with less than 50% decrease in the intensity of depression after 8 weeks of treatment with selective serotonin reuptake inhibitors were recruited. Thirty patients (16 women) with a mean (SD) age of 47.2 (12.0) years were randomly allocated to 2 groups. For the active group we administered 2-mA stimulation 20 minutes for each session, with 30 seconds ramp-up from 0 and 30 seconds ramp-down. For the sham group we administered 30 seconds ramp-up to 2 mA, 10 seconds stimulation, 30 seconds ramp-down, and 20 minutes no current. The anode was fixed on the center of F3, and the cathode on F4, over the dorsolateral prefrontal cortex. We assessed the Hamilton Depression Rating Scale at the baseline (mean difference = 1.0, P = .630), at the last session of tDCS, and at 1-month postintervention. There were statistically significant differences in the mean Hamilton scores after the intervention, and 1 month later in favor of active group; P < .001, and P = .003, respectively. Mixed analysis of variance showed a significant difference in the mean scores for active group P = .010 and pattern of change during the study P < .001 in favor of active intervention. We concluded that tDCS is an efficient therapy for patients with resistant major depression, and the benefits would remain at least for 1 month.

A safety study of 500 μA cathodal transcranial direct current stimulation in rat

Background

Transcranial direct current stimulation (tDCS) is a noninvasive neural control technology that has become a research hotspot. To facilitate further research of tDCS, the biosafety of 500 μA cathodal tDCS, a controversial parameter in rats was evaluated.

Results

24 animals were randomly divided into two groups: a cathodal tDCS group (tDCS, n = 12) and control group (control, n = 12). Animals in the tDCS group received 5 consecutive days of cathodal tDCS (500 μA, 15 min, once per day) followed by a tDCS-free interval of 2 days and 5 additional days of stimulation, totally two treatments of tDCS for a total of 10 days. Computational 3D rat model was adopted to calculate the current density distributions in brain during tDCS treatment. Essential brain functions including motor function and learning and memory ability were evaluated. Additionally, to estimate the neurotoxicity of tDCS, the brain morphology, neurotransmitter levels and cerebral temperature were investigated. Our results showed that the current density inside the brain was less than 20 A/m² during tDCS treatment in computational model. tDCS did not affect motor functions and learning and memory ability after tDCS treatment. In addition, no significant differences were found for the tDCS group in hematology, serum biochemical markers or the morphology of major organs. Moreover, tDCS treatment had no effect on the brain morphology, neural structures, neurotransmitter levels or cerebral temperature.

Conclusion

500 μA cathodal tDCS as performed in the present study was safe for rodents.

Electronic supplementary material

The online version of this article (10.1186/s12868-019-0523-7) contains supplementary material, which is available to authorized users.

Does transcranial direct current stimulation to the prefrontal cortex affect social behavior? A meta-analysis

This meta-analysis (k = 48, N = 2196) examined the effect of transcranial direct current brain stimulation (tDCS) applied to the prefrontal cortex on a variety of social behaviors, including aggression, overeating, impulsivity, bias, honesty, and risk-taking. tDCS showed an overall significant effect on reducing undesirable behaviors, with an average effect size of d = −0.20. tDCS was most effective at reducing risk-taking behavior, bias, and overeating. tDCS did not affect aggression, impulsivity, or dishonesty. We examined moderators such as brain region of interest, online vs offline stimulation, within- vs between-subjects designs, dose, and duration, but none showed significant interactions. We also tested for potential publication bias using two different tools, which indicated signs of publication bias in the literature. After correcting for potential publication bias, the effect of tDCS was still significant, but the size was reduced (d = −0.10). These findings suggest the presence of tDCS studies with null findings outside of the published literature. Taken together, these results suggest that although tDCS can reduce undesirable behaviors, researchers should consider the types of behaviors they measure and use strategies to ensure sufficient power to detect a possible effect of tDCS on social behavior.

Changes in motor cortical excitability in schizophrenia following transcranial direct current stimulation

Schizophrenia is a disorder associated with cortical inhibition deficits. Transcranial direct current stimulation (tDCS) induces changes in cortical excitability in healthy subjects and individuals with neuropsychiatric disorders depending on the stimulation parameters. Our aim was to investigate whether a previously published tDCS protocol associated with symptomatic improvement in schizophrenia would induce changes in motor cortical excitability, assessed by transcranial magnetic stimulation paradigms, i.e., short-interval intracortical inhibition (SICI) and intra-cortical facilitation (ICF). We assessed cortical excitability measurements in 48 subjects with schizophrenia before and after a single session of active tDCS (20 min, 2 mA, anode over left dorsolateral prefrontal cortex, cathode over left temporoparietal cortex) or sham. Those who received active tDCS had a significant increase of SICI in the left motor cortex compared to those who received sham stimulation (Cohen's d = 0.54, p = .019). No changes were observed for ICF. In addition, lower SICI was associated with higher age (β = -0.448, p < .01). Increase in intracortical inhibition may indicate a mechanism of action of tDCS in this population. Future studies should investigate whether this finding is a biomarker of treatment response for schizophrenia.

The Impact of Transcranial Direct Current Stimulation (tDCS) on Bipolar Depression, Mania, and Euthymia: a Systematic Review of Preliminary Data

The neurobiological basis of bipolar disorders (BD) has received increased attention and several brain regions and brain circuits have been correlated with clinical symptoms. These brain regions and circuits may represent targets for neuromodulation techniques such as transcranial Direct Current Stimulation (tDCS). We systematically reviewed the literature to explore the risks and benefits of tDCS in BD and examined all mood states. Following the PRISMA guidelines, a systematic literature search using several databases was performed from April 2002 to June 2017. From the 135 eligible studies, we retained 19 relevant articles for the systematic review, including 170 patients with BD treated by tDCS. Data from 10 studies suggest that tDCS improves depressive symptoms in BD. One case report of add-on-tDCS reported a significant positive response on manic symptoms. In 4 studies, tDCS impacted specific neurocognitive functions in euthymic patients. There is also preliminary evidence that tDCS improves neurological soft signs and sleep quality in euthymia. Side effects were predominantly transient and low-intensity, although 6 cases of hypomanic/manic affective switches have been reported. The majority of studies have been open trials with few patients. More sufficiently powered randomized controlled trials are needed to clarify the effectiveness of tDCS. Preliminary data suggests that tDCS holds promise as a treatment for BD, especially during depressive episodes. Perhaps most promising are emerging data suggesting tDCS may impact neurocognition and sleep quality in euthymia and be useful for relapse prevention.

Beneficial effects of anodal transcranial direct current stimulation (tDCS) on spatial working memory in patients with schizophrenia

Schizophrenia is a severe and often detrimental psychiatric disorder. The individual patients' level of functioning is essentially determined by cognitive, particularly working memory (WM), deficits that are critically linked to dysfunctional activity of the dorsolateral prefrontal cortex (dlPFC). Transcranial direct current stimulation (tDCS) can transiently modulate activity of the dlPFC and remote areas and has been shown to improve WM functions. It may therefore provide a new, targeted treatment option. For this aim, the present study investigated the effect of anodal tDCS of different intensities on spatial WM in patients with schizophrenia. In two experiments, 32 patients performed a spatial n-back task with increasing WM load (1-, 2-, and 3-back) at baseline and in two sessions with anodal or sham tDCS (EXP I [n = 16]: 1 mA; EXP II [n = 16]: 2 mA) to the right dlPFC (cathode: left m. deltoideus). With 1 mA anodal tDCS, no effect on WM performance could be detected. However, 2 mA anodal tDCS increased accuracy (measured by d') of the task with the highest WM load (3-back). This effect was larger in patients with a lower level of general neurocognitive functioning. These results demonstrate a beneficial effect of 2 mA anodal tDCS on deficient WM accuracy in patients with schizophrenia particularly under challenging conditions and in subjects with higher cognitive impairments. This data will inform future clinical trials on tDCS-enhanced cognitive training to improve treatment of schizophrenia.