Neurocognitive effects of transcranial direct current stimulation (tDCS) in unipolar and bipolar depression: Findings from an international randomized controlled trial

Efficacy of non-invasive brain stimulation and neuronavigation for major depressive disorder: a systematic review and meta-analysis

INTRODUCTION

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are increasingly used for major depressive disorder (MDD). Most tDCS and rTMS studies target the left dorsolateral prefrontal cortex, either with or without neuronavigation. We examined the effect of rTMS and tDCS, and the added value of neuronavigation in the treatment of MDD.

METHODS

A search on PubMed, Embase, and Cochrane databases for rTMS or tDCS randomized controlled trials of MDD up to 1 February 2023, yielded 89 studies. We then performed meta-analyses comparing tDCS efficacy to non-neuronavigated rTMS, tDCS to neuronavigated rTMS, and neuronavigated rTMS to non-neuronavigated rTMS. We assessed the significance of the effect in subgroups and in the whole meta-analysis with a z-test and subgroup differences with a chi-square test.

RESULTS

We found small-to-medium effects of both tDCS and rTMS on MDD, with a slightly greater effect from rTMS. No significant difference was found between neuronavigation and non-neuronavigation.

CONCLUSION

Although both tDCS and rTMS are effective in treating MDD, many patients do not respond. Additionally, current neuronavigation methods are not significantly improving MDD treatment. It is therefore imperative to seek personalized methods for these interventions.

The Application of tDCS to Treat Pain and Psychocognitive Symptoms in Cancer Patients: A Scoping Review

Background

The use of transcranial direct current stimulation (tDCS) to modulate pain, psychological aspects, and cognitive functions has increased in recent years. The present scoping review aims to investigate the use of tDCS in cancer patients and its significant impact on psychocognitive and pain related symptoms.

Methods

From the earliest available date to June 2023, a comprehensive search was conducted in three electronic scientific databases-PubMed, Scopus, and Embase-and other supplementary sources. Ten relevant studies were identified and included, comprising single case studies, randomized controlled trials, pilot studies, and one retrospective study. PRISMA guidelines for scoping reviews were followed.

Results

These studies investigated the use of tDCS to improve pain and psychocognitive aspects in patients with various types of cancer, including breast, oral, bladder, lung, pancreatic, head and neck cancer, hepatocellular carcinoma, and meningioma. Overall, the results suggest that tDCS has shown efficacy in relieving pain, reducing anxiety and depression, and improving cognitive function in cancer patients.

Conclusion

Due to the limited number and high heterogeneity of the existing literature in this field, more investigation and the establishment of standardized protocols would be required to obtain more conclusive evidence.

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.

The effectiveness of microcurrent neurofeedback on depression, anxiety, post-traumatic stress disorder, and quality of life

BACKGROUND

The world faces a mental health crisis with elevated rates of depression, anxiety, and post-traumatic stress, leaving a profound impact on daily quality of life (QOL). Current treatments show varying degrees of efficacy and carry burdensome challenges. Evidence exists for use of an innovative neurotechnology to reduce symptoms of depression, anxiety, and post-traumatic stress disorder (PTSD), but the science is lacking for use in the general population.

PURPOSES

The purpose of this pilot study was to explore the effects of microcurrent neurofeedback on depression, anxiety, PTSD symptoms, and QOL in adults.

METHODOLOGY

This was a one-group, exploratory pilot study that tested outcomes of depression, anxiety, PTSD risk, suicide risk, and QOL in 20 adults using convenience sampling. IASIS microcurrent neurofeedback (I-MCN) was the intervention that was delivered twice a week for 10 weeks; data collection was baseline, 5 weeks, and 10 weeks.

RESULTS

Depression, anxiety, PTSD risk, and QOL improved significantly by the 10th and 20th session; suicidal risk showed nonsignificant reduction. Use of a more feasible interventional procedure established a foundation for use in clinical settings for the population.

CONCLUSIONS

Using a more simpler procedure than what was used in a previous study reflected positive outcomes earlier and sustained over 10 weeks. This safe and effective technology carries rare but easily overcome adverse effects and could be an alternative to existing treatments or treatment-resistant conditions.

IMPLICATIONS

Advanced practice nurses can apply the evidence to reduce symptoms of depression, anxiety, and PTSD. Randomized controlled trials and testing on diverse populations are needed.

Non-invasive brain stimulation for patients and healthy subjects: Current challenges and future perspectives

Non-invasive brain stimulation (NIBS) techniques have a rich historical background, yet their utilization has witnessed significant growth only recently. These techniques encompass transcranial electrical stimulation and transcranial magnetic stimulation, which were initially employed in neuroscience to explore the intricate relationship between the brain and behaviour. However, they are increasingly finding application in research contexts as a means to address various neurological, psychiatric, and neurodegenerative disorders. This article aims to fulfill two primary objectives. Firstly, it seeks to showcase the current state of the art in the clinical application of NIBS, highlighting how it can improve and complement existing treatments. Secondly, it provides a comprehensive overview of the utilization of NIBS in augmenting the brain function of healthy individuals, thereby enhancing their performance. Furthermore, the article delves into the points of convergence and divergence between these two techniques. It also addresses the existing challenges and future prospects associated with NIBS from ethical and research standpoints.

Associations of BDNF/BDNF-AS SNPs with Depression, Schizophrenia, and Bipolar Disorder

Brain-Derived Neurotrophic Factor (BDNF) is crucial for various aspects of neuronal development and function, including synaptic plasticity, neurotransmitter release, and supporting neuronal differentiation, growth, and survival. It is involved in the formation and preservation of dopaminergic, serotonergic, GABAergic, and cholinergic neurons, facilitating efficient stimulus transmission within the synaptic system and contributing to learning, memory, and overall cognition. Furthermore, BDNF demonstrates involvement in neuroinflammation and showcases neuroprotective effects. In contrast, BDNF antisense RNA (BDNF-AS) is linked to the regulation and control of BDNF, facilitating its suppression and contributing to neurotoxicity, apoptosis, and decreased cell viability. This review article aims to comprehensively overview the significance of single nucleotide polymorphisms (SNPs) in BDNF/BDNF-AS genes within psychiatric conditions, with a specific focus on their associations with depression, schizophrenia, and bipolar disorder. The independent influence of each BDNF/BDNF-AS gene variation, as well as the interplay between SNPs and their linkage disequilibrium, environmental factors, including early-life experiences, and interactions with other genes, lead to alterations in brain architecture and function, shaping vulnerability to mental health disorders. The potential translational applications of BDNF/BDNF-AS polymorphism knowledge can revolutionize personalized medicine, predict disease susceptibility, treatment outcomes, and guide the selection of interventions tailored to individual patients.

BDNF and stress/mood-related interactions on emotional disorder symptoms, executive functioning, and deliberate self-harm

Some prior research has suggested that the brain-derived neurotrophic factor (BDNF) gene may amplify responses related to life stress (e.g., depression and anxiety) or associated with negative moods (e.g., self-harm and diminished cognitive functioning). The purpose of this study was to investigate whether stress/mood-related associations with depressive and anxiety symptoms, deliberate self-harm, and executive functioning (EF) are moderated by genotypic variations in BDNF rs10835210 (a relatively understudied BDNF polymorphism) in a nonclinical sample. As part of a larger study, European American social drinkers (N = 132; 43.9% female; M age = 26.0, SD = 7.6) were genotyped for BDNF rs10835210 and were administered self-report measures of subjective life stress, depressive and anxiety symptoms, and history of non-suicidal self-injury (NSSI) and behavioral measures of EF and deliberate self-harm. Results indicated that BDNF significantly moderated the life stress associations with depressive symptoms and NSSI, the anxious mood association with EF, and the depressed mood association with deliberate self-harm behavior. Each of these BDNF × stress/mood interactions were characterized by stress/mood associations that were stronger in individuals with the AA genotype (homozygous for the minor allele) than in individuals possessing a genotype that included the major allele (AC or CC). The main limitations of the present study were use of a cross-sectional design, modest sample size, and investigating only one BDNF polymorphism. Despite these limitations and though preliminary, current findings suggest that variations in BDNF may confer vulnerability to stress or mood, which may result in more adverse emotional, cognitive, or behavioral outcomes.

An update on potential pharmacotherapies for cognitive impairment in bipolar disorder

INTRODUCTION

Cognitive impairment is a core feature of bipolar disorder (BD) that impedes recovery by preventing the return to optimal socio-occupational functioning and reducing quality of life. Presently, there are no efficacious treatments for cognitive impairment in BD, but many pharmacological interventions are being considered as they have the potential to target the underlying pathophysiology of the disorder.

AREAS COVERED

This review summarizes the available evidence for pharmacological interventions for cognitive impairment in bipolar disorder. We searched PubMed, MedLine, and PsycInfo from inception to December 1^st, 2022. Traditional treatments, such as lithium, anticonvulsants (lamotrigine), antipsychotics (aripiprazole, asenapine, cariprazine, lurasidone, and olanzapine), antidepressants (vortioxetine, fluoxetine, and tianeptine) and psychostimulants (modafinil), and emerging interventions, such as acetylcholinesterase inhibitors (galantamine and donepezil), dopamine agonists (pramipexole), erythropoietin, glucocorticoid receptor antagonists (mifepristone), immune modulators (infliximab, minocycline and doxycycline), ketamine, metabolic agents (insulin, metformin, and liraglutide), probiotic supplements, and Withania somnifera are discussed.

EXPERT OPINION

The investigation of interventions for cognitive impairment in BD is a relatively under-researched area. In the past, methodological pitfalls in BD cognition trials have also been a critical limiting factor. Expanding on the existing literature and identifying novel pharmacological and non-pharmacological treatments for cognitive impairment in BD should be a priority.

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.

Brain stimulation treatment for bipolar disorder

AIMS

Bipolar disorders are clinically complex, chronic and recurrent disorders. Few treatment options are effective across hypomanic, manic, depressive and mixed states and as continuation or maintenance treatment after initial symptom remission. The aim of this review was to provide an up-to-date overview of research on the efficacy, tolerability and cognitive effects of electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), magnetic seizure therapy (MST), deep brain stimulation (DBS) and vagus nerve stimulation (VNS).

METHODS

References included in this review were identified through multiple searches of the Embase, PubMed/MEDLINE and APA PsycINFO electronic databases for articles published from inception until February 2022. Published reviews, meta-analyses, randomised controlled trials and recent studies were prioritised to provide a comprehensive and up-to-date overview of research on brain stimulation in patients with bipolar disorders.

RESULTS

The evidence base for brain stimulation as an add-on or alternative to pharmacological and psychological treatments in patients with bipolar disorders is limited but rapidly expanding. Brain stimulation treatments represent an opportunity to treat all bipolar disorder states, including cognitive dysfunction during euthymic periods.

CONCLUSION

Whilst findings to date have been encouraging, larger randomised controlled trials with long-term follow-up are needed to clarify important questions regarding treatment efficacy and tolerability, the frequency of treatment-emergent affective switches and effects on cognitive function.

Using Bilateral tDCS to Modulate EEG Amplitude and Coherence of Men With Opioid Use Disorder Under Methadone Therapy: A Sham-controlled Clinical Trial

Objective. This study aimed to investigate the effect of bilateral transcranial direct current stimulation (tDCS) on the electroencephalography (EEG) amplitude and coherence in male patients with opioid use disorder (OUD), who were under methadone therapy. It compares the effects of active versus sham tDCS. Methods. This is a double-blind sham-controlled clinical trial. Participants were 30 male patients with OUD; they were divided into 3 groups of left anode/right cathode tDCS, right anode/left cathode tDCS, and sham tDCS. Their brainwave activity was measured by quantitative EEG before study and then active groups underwent tDCS (2 mA, 20 min) applied over their right/left dorsolateral prefrontal cortex (DLPFC) for 10 consecutive days. After stimulation, they were re-assessed. The collected data were analyzed in SPSS, MATLAB, and NeuroGuide v.2 applications. Results. After active tDCS, a significant decrease in amplitude of slow brain waves (delta, theta, and alpha) in prefrontal, frontal, occipital, and parietal areas, and an increase in the coherence of beta, delta, and theta frequency bands in the parietal, central, and temporal regions of addicts were reported. In the sham group, there was a significant decrease in the amplitude of the alpha wave and in the coherence of delta and theta waves. Conclusion. The active tDCS over the right/left DLPFC, as a noninvasive and complementary treatment, can modulate the amplitude and coherence of brainwaves in patients with OUD.

Role of Catechol-O-methyltransferase Val158Met Polymorphism on Transcranial Direct Current Stimulation in Swallowing

Transcranial direct current stimulation (tDCS) is one of the latest post-stroke dysphagia treatment modalities, and the effect of tDCS is known to be affected by various factors including genetic polymorphisms. However, the role of catechol-O-methyltransferase (COMT) polymorphisms on tDCS in swallowing is unclear. In this prospective pilot study, we aim to explore the effect of tDCS on the swallowing cortex and subsequent swallowing motor function according to COMT polymorphism. Twenty-four healthy participants received either anodal tDCS or sham mode tDCS on the mylohyoid motor cortex at random order, after inhibitory repetitive transcranial magnetic stimulation (rTMS) for preconditioning. The primary outcome was the changes of mylohyoid-motor-evoked potentials (MH-MEP) amplitude in each COMT polymorphism group, from the post-inhibitory rTMS baseline state to immediate, 30, and 60 min after tDCS. The secondary outcomes were the changes in swallowing function. The results showed that COMT Val/Val polymorphism showed improvement across time in the MH-MEP amplitudes and triggering time of swallowing after tDCS, whereas COMT Met carrier group did not show significant changes of MH-MEP or swallowing function across time. This therapeutic response variability of tDCS in the mylohyoid motor system according to COMT polymorphism support the importance of genetic analysis in individualized dysphagia treatment.

Effect of medication therapy combined with transcranial direct current stimulation on depression and response inhibition of patients with bipolar disorder type I: a clinical trial

OBJECTIVE

Bipolar Disorder (BD) is one of the most common mental disorders associated with depressive symptoms and impairment in executive functions such as response inhibition. This study aimed to investigate the effectiveness of medication therapy combined with Transcranial Direct Current Stimulation (tDCS) on depression and response inhibition of patients with BD.

METHOD

This is a double-blinded randomized clinical trial with pretest, posttest, and follow-up design. Participants were 30 patients with BD randomly assigned to two groups of Medication+tDCS (n = 15, receiving medications plus tDCS with 2 mA intensity over dorsolateral prefrontal cortex for 10 days, two sessions per day each for 20 min) and Medication (n = 15, receiving mood stabilizers including 2-5 tables of 300 mg (mg) lithium, 200 mg sodium valproate, and 200 mg carbamazepine two times per day). Pretest, posttest and 3-month follow-up assessments were the 21-item Hamilton Depression Rating Scale (HDRS) and a Go/No-Go test. Collected data were analyzed in SPSS v.20 software.

RESULTS

The mean HDRS score in both groups was reduced after both interventional techniques, where the group received combined therapy showed more reduction (P < 0.01), although their effects were not maintained after 3 months. In examining response inhibition variable, only the combined therapy could reduce the commission error of patients under a go/no-go task (p < 0.05), but its effect was not maintained after 3 months. There was no significant difference in the group received medication therapy alone.

CONCLUSION

Medication in combination with tDCS can reduce the depressive symptoms and improve the response inhibition ability of people with BD.

TRIAL REGISTRATION

This study was registred by Iranian Registry of Clinical Trials (Parallel, ID: IRCT20191229045931N1 , Registration date: 24/08/2020).

Effect of Catechol-O-Methyltransferase Genotype Polymorphism on Neurological and Psychiatric Disorders: Progressing Towards Personalized Medicine

Different polymorphisms of the catechol-O-methyltransferase (COMT) gene affect the COMT enzyme activity. The COMT enzyme plays a major role in the pathophysiology of various neurological and psychiatric disorders. This review article aims to discuss what recent research has discovered about the association of COMT genotype polymorphism with neurological and psychiatric disorders and the scope for the knowledge to be applied for advancement in therapeutics. We searched PubMed and Google Scholar databases and found 1656 articles. We included observational studies, clinical trials, and meta-analyses in the English language published between 2019 and 2021. We screened the articles based on the title and the abstract and found 26 relevant articles. Diseases or conditions studied primarily were schizophrenia, Parkinson’s disease, Alzheimer’s disease, substance use, and depression. This article highlights how genetics influences the susceptibility of an individual to neurological and psychiatric diseases and the variations in the specific symptoms of those diseases. The review showed that the variability in individual response to therapeutic interventions stems from the gene level. This knowledge can contribute towards the dawn of a new era of personalized medicine.

The effect of bilateral tDCS over dorsolateral prefrontal cortex on the cognitive abilities of men with opioid use disorder under methadone therapy: A sham-controlled clinical trial

Background/aim

Opioid use disorder (OUD) can have negative impact on cognitive functions. This study aims to evaluate the effect of bilateral transcranial direct-current stimulation (tDCS) over the right/left dorsolateral prefrontal cortex (DLPFC) on the cognitive abilities of OUD men.

Methods

This study is a double-blind sham-controlled randomized clinical trial with a pretest/posttest design. Participants were 31 men with OUD living in Zanjan, Iran, assigned to three groups of left anode/right cathode tDCS, right anode/left cathode tDCS, and sham tDCS. The two active groups received tDCS (2 mA) at 10 sessions each for 10–20 min. The Cognitive Abilities Questionnaire (CAQ) in Persian was used to measure their cognitive abilities before and after intervention. Collected data were analyzed in SPSS v.22 software.

Results

Bilateral DLPFC stimulation resulted in a significant improvement in cognitive flexibility, planning, decision making, inhibitory control/selective attention, and memory of patients in the two active tDCS groups, while the sham tDCS had no significant effect on their cognitive abilities.

Conclusion

Bilateral tDCS over DLPFC, as an effective and complementary treatment, can improve the cognitive abilities of men with OUD.

Trial registration: This study is a double-blind sham-controlled clinical trial (Parallel, IRCT20170513033946N5. Registered 19 Jan 2019, https://en.irct.ir/trial/36081).

Transcranial direct current stimulation combined with alcohol cue inhibitory control training reduces the risk of early alcohol relapse: A randomized placebo-controlled clinical trial

BACKGROUND

Approximately half of all people with alcohol use disorder (AUD) relapse into alcohol reuse in the next few weeks after a withdrawal treatment. Brain stimulation and cognitive training represent recent forms of complementary interventions in the context of AUD.

OBJECTIVE

To evaluate the clinical efficacy of five sessions of 2 mA bilateral transcranial direct current stimulation (tDCS) for 20 min over the dorsolateral prefrontal cortex (DLPFC) (left cathodal/right anodal) combined with alcohol cue inhibitory control training (ICT) as part of rehabilitation. The secondary outcomes were executive functioning (e.g. response inhibition) and craving intensity, two mechanisms strongly related to abstinence.

METHODS

A randomized clinical trial with patients (n = 125) with severe AUD at a withdrawal treatment unit. Each patient was randomly assigned to one of four conditions, in a 2 [verum vs. sham tDCS] x 2 [alcohol cue vs. neutral ICT] factorial design. The main outcome of treatment was the abstinence rate after two weeks or more (up to one year).

RESULTS

Verum tDCS improved the abstinence rate at the 2-week follow-up compared to the sham condition, independently of the training condition (79.7% [95% CI = 69.8-89.6] vs. 60.7% [95% CI = 48.3-73.1]; p = .02). A priori contrasts analyses revealed higher abstinence rates for the verum tDCS associated with alcohol cue ICT (86.1% [31/36; 95% CI = 74.6-97.6]) than for the other three conditions (64% [57/89; 95% CI = 54-74]). These positive clinical effects on abstinence did not persist beyond two weeks after the intervention. Neither the reduction of craving nor the improvement in executive control resulted specifically from prefrontal-tDCS and ICT.

CONCLUSIONS

AUD patients who received tDCS applied to DLPFC showed a significantly higher abstinence rate during the weeks following rehabilitation. When combined with alcohol specific ICT, brain stimulation may provide better clinical outcomes.

TRIAL REGISTRATION

ClinicalTrials.gov number NCT03447054 https://clinicaltrials.gov/ct2/show/NCT03447054.

Frontotemporal Transcranial Direct Current Stimulation Decreases Serum Mature Brain-Derived Neurotrophic Factor in Schizophrenia

Although transcranial direct current stimulation (tDCS) shows promise as a treatment for auditory verbal hallucinations in patients with schizophrenia, mechanisms through which tDCS may induce beneficial effects remain unclear. Evidence points to the involvement of neuronal plasticity mechanisms that are underpinned, amongst others, by brain-derived neurotrophic factor (BDNF) in its two main forms: pro and mature peptides. Here, we aimed to investigate whether tDCS modulates neural plasticity by measuring the acute effects of tDCS on peripheral mature BDNF levels in patients with schizophrenia. Blood samples were collected in 24 patients with schizophrenia before and after they received a single session of either active (20 min, 2 mA, n = 13) or sham (n = 11) frontotemporal tDCS with the anode over the left prefrontal cortex and the cathode over the left temporoparietal junction. We compared the tDCS-induced changes in serum mature BDNF (mBDNF) levels adjusted for baseline values between the two groups. The results showed that active tDCS was associated with a significantly larger decrease in mBDNF levels (mean −20% ± standard deviation 14) than sham tDCS (−8% ± 21) (F = 5.387; p = 0.030; η² = 0.205). Thus, mature BDNF may be involved in the beneficial effects of frontotemporal tDCS observed in patients with schizophrenia.

Efficacy and acceptability of transcranial direct current stimulation for treating depression: A meta-analysis of randomized controlled trials

BACKGROUND

Transcranial direct current stimulation (tDCS) is a promising nonpharmacological intervention for treating depression. We aimed to provide an updated meta-analysis assessing the anti-depressant efficacy of tDCS.

METHODS

We searched the literature from the first available date to 30 December 2020 to identify relevant randomized controlled trials (RCTs).

RESULTS

27 RCTs (N = 1204 patients, 653 in active tDCS and 551 in sham tDCS) were included. Active tDCS was superior to sham tDCS (g = 0.46, 95 % CI 0.15-0.76) in modulating depressive symptoms measured by depression rating scales. Active tDCS was also superior to sham tDCS in reducing response and remission rates, but these differences did not reach statistically significant levels (OR_response = 1.75, 95 % CI 0.85-3.58; OR_remission = 1.29, 95 % CI 0.59-2.83). The two groups had comparable dropout rates (OR = 1.28, 95 % CI 0.62-1.64).

CONCLUSION

For treatments of depressive episodes, tDCS may be efficacious. Specific tDCS parameters (e.g., a 2-mA stimulation current and 30-min sessions) and clinical characteristics (e.g., antidepressant-free) may augment the treatment efficacy of tDCS.

A sham-controlled clinical trial to examine the effect of bilateral tDCS on craving, TNF-α and IL-6 expression levels, and impulsivity of males with opioid use disorder

BACKGROUND

Opioid use disorder (OUD) is one of the problems and concerns of all countries in the world. On the other hand, transcranial direct current stimulation (tDCS) has been used as a new therapeutic intervention in various psychiatric disorders.

OBJECTIVE

This study aimed to investigate the effect of bilateral tDCS on the expression levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), craving and impulsive behaviors of male patients with OUD.

METHODS

This is a double-blind sham-controlled clinical trial. Participants were 31 male patients with OUD divided into three groups of left anode/right cathode tDCS, right anode/left cathode tDCS, and sham tDCS. They received active tDCS (2 mA, 20 min), applied over their dorsolateral prefrontal cortex (DLPFC) for 10 consecutive days. Expression levels of IL-6 and TNF-α cytokines were measured using ELISA method, and the Desires for Drug Questionnaire and the Barratt Impulsiveness Scale version 11 were used to assess the craving and impulsivity of subjects, respectively.

RESULTS

Both active and sham tDCS could significantly reduce drug craving in subjects (p < 0.05). Active tDCS over the right/left DLPFC significantly reduced impulsivity and its dimensions (overall, attentional, motor, and nonplanning) compared to the sham tDCS (p < 0.05). It could also reduce the expression levels of IL-6 and TNF-α, but the difference was not statistically significant.

CONCLUSIONS

The active tDCS over the right/left DLPFC, as a noninvasive and complementary treatment, can be used along with other common methods for the treatment of patients with OUD. It can improve their cognitive functions by reducing impulsivity.

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.

Cognitive outcomes of the bipolar depression electrical treatment trial (BETTER): a randomized, double-blind, sham-controlled study

Bipolar depression is associated with marked cognitive deficits. Pharmacological treatments for this condition are limited and may aggravate depressive and cognitive symptoms. Therefore, therapeutic interventions that preserve adequate cognitive functioning are necessary. Our previous results demonstrated significant clinical efficacy of transcranial direct current stimulation (tDCS) in the Bipolar Depression Electrical Treatment Trial (BETTER). Here, cognitive outcomes of this study are reported. We randomized 59 patients with bipolar disorder I or II in an acute depressive episode to receive active (12 2 mA, 30-min, anodal-left, cathodal-right prefrontal cortex tDCS sessions) or sham tDCS. Patients were on stable pharmacological regimen for at least 2 weeks. A battery of 12 neuropsychological assessments in five cognitive domains (attention and processing speed, memory, language, inhibitory control, and working memory and executive function) was performed at baseline, after two weeks and at endpoint (week 6). No significant differences between groups over 6 weeks of treatment were observed for any cognitive outcomes. Moreover, no decrease in cognitive performance was observed. Our findings warrant further replication in larger studies. Trial Registration: clinicaltrials.gov Identifier: NCT02152878.

Effects of unilateral tDCS over left prefrontal cortex on emotion regulation in depression: Evidence from concurrent functional magnetic resonance imaging

Major depressive disorder (MDD) is the most common mood disorder and a primary cause of disability worldwide. MDD symptomatology entails disturbances in emotion regulation, namely one's ability to modify the intensity and duration of emotional reactions towards affective events. Transcranial direct current stimulation (tDCS) has emerged as a promising treatment for MDD. Yet, positive tDCS outcomes vary across studies, while the precise effects of the procedure for cortical excitability in MDD during emotion regulation remain largely unexplored. Here, we leveraged functional magnetic resonance imaging (fMRI)-compatible tDCS technology to examine the functional consequences of a unilateral anodal tDCS montage at 1.5 mA over left PFC (area F3; with the reference electrode over an extracephalic location) for brain activity during an emotion-regulation task in MDD patients and age-matched healthy control subjects. Our results revealed down-regulation of negative emotions in the right amygdala and visual cortex of healthy controls but not MDD patients prior to stimulation, the degree of which correlated with the magnitude of the participants' reappraisal scores. TDCS did not elicit significant changes in neural activation patterns for either group. These findings contribute to the literature on the pathophysiology of MDD by showing that a key disturbance in the disorder entails the ineffective down-regulation of activity not only within the amygdala, but also within visual cortical areas in response to negative information. Further, these results suggest that relative to bifrontal tDCS montages, unilateral stimulation of moderate intensity over left PFC may not be sufficient to elicit therapeutic effects for MDD.

Anodal and cathodal tDCS modulate neural activity and selectively affect GABA and glutamate syntheses in the visual cortex of cats

KEY POINTS

The present study showed that anodal and cathodal transcranial direct current stimulation (tDCS) can respectively increase and decrease the amplitude of visually evoked field potentials in the stimulated visual cortex of cats, with the effect lasting for ∼60-70 min. We directly measured tDCS-induced changes in the concentration of inhibitory and excitatory neurotransmitters in the visual cortex using the enzyme-linked immunosorbent assay method and showed that anodal and cathodal tDCS can selectively decrease the concentration of GABA and glutamate in the stimulated cortical area. Anodal and cathodal tDCS can selectively inhibit the synthesis of GABA and glutamate by suppressing the expression of GABA- and glutamate-synthesizing enzymes, respectively.

ABSTRACT

Transcranial direct current stimulation (tDCS) evokes long-lasting neuronal excitability in the target brain region. The underlying neural mechanisms remain poorly understood. The present study examined tDCS-induced alterations in neuronal activities, as well as the concentration and synthesis of GABA and glutamate (GLU), in area 21a (A21a) of cat visual cortex. Our analysis showed that anodal and cathodal tDCS respectively enhanced and suppressed neuronal activities in A21a, as indicated by a significantly increased and decreased amplitude of visually evoked field potentials (VEPs). The tDCS-induced effect lasted for ∼60-70 min. By contrast, sham tDCS had no significant impact on the VEPs in A21a. On the other hand, the concentration of GABA, but not that of GLU, in A21a significantly decreased after anodal tDCS relative to sham tDCS, whereas the concentration of GLU, but not that of GABA, in A21a significantly decreased after cathodal tDCS relative to sham tDCS. Furthermore, the expression of GABA-synthesizing enzymes GAD65 and GAD67 in A21a significantly decreased in terms of both mRNA and protein concentrations after anodal tDCS relative to sham tDCS, whereas that of GLU-synthesizing enzyme glutaminase (GLS) did not change significantly after anodal tDCS. By contrast, both mRNA and protein concentrations of GLS in A21a significantly decreased after cathodal tDCS relative to sham tDCS, whereas those of GAD65/GAD67 showed no significant change after cathodal tDCS. Taken together, these results indicate that anodal and cathodal tDCS may selectively reduce GABA and GLU syntheses and thus respectively enhance and suppress neuronal excitability in the stimulated brain area.

Global functional connectivity density alterations in patients with bipolar disorder with auditory verbal hallucinations and modest short-term effects of transcranial direct current stimulation augmentation treatment-Baseline and follow-up study

OBJECTIVES

To investigate the neuroimaging characteristics of auditory verbal hallucinations (AVHs) in patients with bipolar disorder (BP) experiencing depressive episodes with and without AVHs, and alterations in those characteristics after transcranial direct current stimulation (tDCS).

METHODS

For a baseline pilot study, we recruited 80 patients with BP and depressive status (40 with and 40 without AVHs), and 40 healthy controls (HCs). Their global functional connectivity density (gFCD) was screened by functional magnetic resonance imaging (fMRI). Voxel-wise one-way analysis of covariance (ANCOVA) was conducted to detect intergroup differences in gFCD. In a follow-up study, the effects of 5 weeks of tDCS augmentation treatment on clinical symptoms and gFCD were assessed in the 40 BP patients with AVHs.

RESULTS

Compared to HCs, BP patients with and without AVHs exhibited increased gFCD in the central parietal lobe, insular lobe, and middle cingulate cortex, with decreased gFCD in the posterior parietal cortex, lateral prefrontal cortex, and occipital lobe (all bilateral). Only patients with AVHs showed increased gFCD in the Broca and Wernicke regions, and decreased gFCD in the hippocampus (all bilateral). After 5 weeks of tDCS, AVHs were slightly alleviated and gFCD abnormalities in the hippocampus were mildly attenuated.

CONCLUSIONS

Patients with BP and AVHs showed disturbances in the brain's communication capacity mainly in the left frontoparietal network, control network, and memory circuitry. Five weeks of tDCS alleviated AVHs slightly, without improving depressive symptoms, and attenuated hippocampal gFCD alterations in these patients.