Transcranial direct current stimulation in patients with obsessive compulsive disorder: A randomized controlled trial

Investigating brain structure and tDCS response in obsessive-compulsive disorder

Obsessive-Compulsive Disorder (OCD) is characterized by intrusive thoughts and repetitive behaviors, with associated brain abnormalities in various regions. This study explores the correlation between neural biomarkers and the response to transcranial Direct Current Stimulation (tDCS) in OCD patients. Using structural MRI data from two tDCS trials involving 55 OCD patients and 28 controls, cortical thickness, and gray matter morphometry was analyzed. Findings revealed thicker precentral and paracentral areas in OCD patients, compared to control (p < 0.001). Correlations between cortical thickness and treatment response indicated a significant association between a thinner precentral area and reduced Yale-Brown Obsessive Compulsive Scale (YBOCS) scores (p = 0.02). While results highlight the complexity of treatment response predictors, this study sheds light on potential neural markers for tDCS response in OCD patients. Further investigations with larger datasets are warranted to better understand the underpinnings of these biomarkers and their implications for personalized treatment approaches.

Transcranial direct current stimulation as early augmentation in adolescent obsessive compulsive disorder: A pilot proof-of-concept randomized control trial

BACKGROUND

Transcranial direct current stimulation (tDCS) is proven to be safe in treating various neurological conditions in children and adolescents. It is also an effective method in the treatment of OCD in adults.

AIM

To assess the safety and efficacy of tDCS as an add-on therapy in drug-naive adolescents with OCD.

METHODS

We studied drug-naïve adolescents with OCD, using a Children's Yale-Brown obsessive-compulsive scale (CY-BOCS) scale to assess their condition. Both active and sham groups were given fluoxetine, and we applied cathode and anode over the supplementary motor area and deltoid for 20 min in 10 sessions. Reassessment occurred at 2, 6, and 12 wk using CY-BOCS.

RESULTS

Eighteen adolescents completed the study (10-active, 8-sham group). CY-BOCS scores from baseline to 12 wk reduced significantly in both groups but change at baseline to 2 wk was significant in the active group only. The mean change at 2 wk was more in the active group (11.8 ± 7.77 vs 5.25 ± 2.22, P = 0.056). Adverse effects between the groups were comparable.

CONCLUSION

tDCS is safe and well tolerated for the treatment of OCD in adolescents. However, there is a need for further studies with a larger sample population to confirm the effectiveness of tDCS as early augmentation in OCD in this population.

Treating refractory obsessive compulsive disorder with cathodal transcranial direct current stimulation over the supplementary motor area: a large multisite randomized sham-controlled double-blind study

Background

The present study evaluated the therapeutic efficacy and tolerability of 10 transcranial direct current stimulation (tDCS) sessions in treatment-resistance obsessive-compulsive disorder (OCD) patients using a multisite double-blind sham-controlled design.

Methods

Eighty treatment-resistance outpatients suffering from obsessive-compulsive disorder were randomized to receive either active or sham transcranial direct current stimulation. The cathode was positioned over the supplementary motor area and the anode over the right supraorbital area. Patients were evaluated at baseline, end of treatment (day 14), one-month follow-up (day 45), and three-month follow-up (day 105) on the Yale-Brown Obsessive Compulsive Scale.

Results

Although a significant interaction between time and treatment was observed, the primary endpoint-measuring the change in Yale-Brown obsessive compulsive scale scores after two weeks-was not achieved. Conversely, the secondary endpoint, which concerned the change in Yale-Brown obsessive compulsive scale scores after three months, was successfully met. It is important to note, however, that there were no significant differences in the percentage of responders and remitters at any of the post-treatment assessments. This suggests that the treatment may not have had a clinically relevant impact. Patients well received the transcranial direct current stimulation treatment, indicating its good tolerability.

Conclusion

This is the largest controlled trial using transcranial direct current stimulation in treatment-resistance obsessive-compulsive disorder patients. Our results indicate the importance of studying the placebo effect in transcranial direct current stimulation and the necessity to consider a long follow-up time to best evaluate the effects of the intervention.

Clinical trial registration

ClinicalTrials.gov, identifier NCT03304600.

Case report: accelerated cathodal HD-tDCS over the right dorsolateral prefrontal cortex in hoarding disorder

Hoarding disorder is an under-recognized condition characterized by the excessive acquisition of possessions and difficulty in disposing of them, which can have dramatic consequences. As hoarding disorder is difficult to treat and associated with high levels of disability in all areas of functioning, there appears to be a critical need to develop novel, tailored therapeutic strategies. Non-invasive brain stimulation techniques hold promise as potential therapeutic interventions for various psychiatric conditions and as a tool to modulate impulsivity when applied over the dorsolateral prefrontal cortex (DLPFC). Therefore, we hypothesized that delivering accelerated cathodal high-definition direct transcranial stimulation (HD-tDCS) over the right DLPFC could be a suitable approach to alleviate symptoms in patients with hoarding disorder. In a case report, we observed beneficial clinical effects on acquisition and depressive symptoms after 15 sessions of three daily 20-min sessions. Accelerated cathodal HD-tDCS over the right DLPFC appears to be a safe and appropriate intervention for patients with hoarding disorder. However, randomized, sham-controlled trials are needed to further validate these encouraging findings.

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.

Disgust-reduction evaluative conditioning (DREC) and brain stimulation in patients with contamination-based obsessive-compulsive disorder: a protocol for a randomized control trial

BACKGROUND

The negative emotional valence of a stimulus can be altered if paired with a pleasant stimulus, a phenomenon referred to as evaluative conditioning. Disgust, as a central emotion in obsessive-compulsive disorder (OCD), particularly in the contamination subtype, may be an appropriate target for such a method. We know that disgust processing and OCD pathophysiology share in some brain areas, including the orbitofrontal cortex, as the neuromodulation techniques targeted in this area have been able to decrease OCD symptoms. We aim to conduct a randomized clinical trial to investigate the evaluative conditioning effect on disgust reduction in patients with contamination-based OCD when administered with or without neuromodulation targeted orbitofrontal cortex.

METHOD

In a single-blind randomized control trial (RCT), 55 patients with contamination-based OCD will be randomly assigned to four arms. In a factorial design, they will receive 10 sessions of evaluative conditioning training (either sham or real) plus cathodal transcranial direct current stimulation (tDCS) over the orbitofrontal cortex (either sham or real). The intensity of disgust experience and clinical symptoms will be investigated as primary outcomes and quantitative electroencephalogram and cognitive functions as secondary outcomes. The data will be collected at three assessment levels: baseline, after completing intervention sessions, and 2-month follow-up.

DISCUSSION

The present RCT is the first study that applies evaluative conditioning training in the OCD clinical sample. It will clarify the effect of the evaluative conditioning method alone and with tDCS on disgust reduction in patients with contamination-based OCD. It will provide initial evidence for such an emotion modulation method in the OCD population. The effect of this emotion-focused protocol on cognitive functions and electroencephalogram components is also of interest.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05907369. Registered on 16 June 2023. Retrospectively registered.

Mapping the neuroanatomical abnormalities in a phenotype of male compulsive rats

Compulsivity is considered a transdiagnostic dimension in obsessive-compulsive and related disorders, characterized by heterogeneous cognitive and behavioral phenotypes associated with abnormalities in cortico-striatal-thalamic-cortical circuitry. The present study investigated the structural morphology of white and gray matter in rats selected for low- (LD) and high- (HD) compulsive drinking behavior on a schedule-induced polydipsia (SIP) task. Regional brain morphology was assessed using ex-vivo high-resolution magnetic resonance imaging (MRI). Voxel-based morphometry of segmented MRI images revealed larger white matter volumes in anterior commissure and corpus callosum of HD rats compared with LD rats. HD rats also showed significantly larger regional volumes of dorsolateral orbitofrontal cortex, striatum, amygdala, hippocampus, midbrain, sub-thalamic nucleus, and cerebellum. By contrast, the medial prefrontal cortex was significantly smaller in HD rats compared with LD rats with no significant group differences in whole brain, ventricular, or cerebrospinal fluid volumes. These findings show that limbic cortico-basal ganglia structures implicated in impulse control disorders are distinct in rats that are vulnerable to develop compulsive behavior. Such abnormalities may be relevant to the etiology of compulsive disorders in humans.

Feasibility, acceptability and practicality of transcranial stimulation in obsessive compulsive symptoms (FEATSOCS): A randomised controlled crossover trial

BACKGROUND

Transcranial direct current stimulation (tDCS) is a non-invasive form of neurostimulation with potential for development as a self-administered intervention. It has shown promise as a safe and effective treatment for obsessive compulsive disorder (OCD) in a small number of studies. The two most favourable stimulation targets appear to be the left orbitofrontal cortex (L-OFC) and the supplementary motor area (SMA). We report the first study to test these targets head-to-head within a randomised sham-controlled trial. Our aim was to inform the design of future clinical research studies, by focussing on the acceptability and safety of the intervention, feasibility of recruitment, adherence to and tolerability of tDCS, and the size of any treatment-effect.

METHODS

FEATSOCS was a randomised, double-blind, sham-controlled, cross-over, multicentre study. Twenty adults with DSM-5-defined OCD were randomised to treatment, comprising three courses of clinic-based tDCS (SMA, L-OFC, Sham), randomly allocated and delivered in counterbalanced order. Each course comprised four 20-min 2 mA stimulations, delivered over two consecutive days, separated by a 'washout' period of at least four weeks. Assessments were carried out by raters who were blind to stimulation-type. Clinical outcomes were assessed before, during, and up to four weeks after stimulation. Patient representatives with lived experience of OCD were actively involved at all stages.

RESULTS

Clinicians showed willingness to recruit participants and recruitment to target was achieved. Adherence to treatment and study interventions was generally good, with only two dropouts. There were no serious adverse events, and adverse effects which did occur were transient and mostly mild in intensity. Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) scores were numerically improved from baseline to 24 h after the final stimulation across all intervention groups but tended to worsen thereafter. The greatest effect size was seen in the L-OFC arm, (Cohen's d = -0.5 [95% CI -1.2 to 0.2] versus Sham), suggesting this stimulation site should be pursued in further studies. Additional significant sham referenced improvements in secondary outcomes occurred in the L-OFC arm, and to a lesser extent with SMA stimulation.

CONCLUSIONS

tDCS was acceptable, practicable to apply, well-tolerated and appears a promising potential treatment for OCD. The L-OFC represents the most promising target based on clinical changes, though the effects on OCD symptoms were not statistically significant compared to sham. SMA stimulation showed lesser signs of promise. Further investigation of tDCS in OCD is warranted, to determine the optimal stimulation protocol (current, frequency, duration), longer-term effectiveness and brain-based mechanisms of effect. If efficacy is substantiated, consideration of home-based approaches represents a rational next step.

TRIAL REGISTRATION

ISRCTN17937049. https://doi.org/10.1186/ISRCTN17937049.

The Effects of Transcranial Direct Current Stimulation in Obsessive-Compulsive Disorder Symptoms: A Meta-Analysis and Integrated Electric Fields Modeling Analysis

Transcranial direct current stimulation (tDCS) has been showing promising effects for the treatment of obsessive-compulsive disorder (OCD), but there is still no conclusion on its efficacy for this disorder. We performed a systematic review and meta-analysis of trials using tDCS for OCD and a computer modeling analysis to evaluate the electric field (EF) strengths of different electrode assemblies in brain regions of interest (ROIs) (PROSPERO-42021262465). PubMed/MEDLINE, Embase, Cochrane Library and Web of Science databases were searched from inception to 25 September 2022. Randomized controlled trials (RCTs) and open-label studies were included. The primary aim was the effect size (Hedges' g) of continuous outcomes and potential moderators of response. For EF modeling, SimNIBS software was used. Four RCTs and four open-label trials were included (n = 241). Results revealed a large effect of tDCS in the endpoint, but no significant effect between active and sham protocols. No predictor of response was found. EF analysis revealed that montages using the main electrode over the (pre)supplementary motor area with an extracephalic reference electrode might lead to stronger EFs in the predefined ROIs. Our results revealed that tDCS might be a promising intervention to treat OCD; however, larger studies are warranted.

Therapeutic potential of brain stimulation techniques in the treatment of mental, psychiatric, and cognitive disorders

Treatment for brain diseases has been disappointing because available medications have failed to produce clinical response across all the patients. Many patients either do not respond or show partial and inconsistent effect, and even in patients who respond to the medications have high relapse rates. Brain stimulation has been seen as an alternative and effective remedy. As a result, brain stimulation has become one of the most valuable therapeutic tools for combating against brain diseases. In last decade, studies with the application of brain stimulation techniques not only have grown exponentially but also have expanded to wide range of brain disorders. Brain stimulation involves passing electric currents into the cortical and subcortical area brain cells with the use of noninvasive as well as invasive methods to amend brain functions. Over time, technological advancements have evolved into the development of precise devices; however, at present, most used noninvasive techniques are repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS), whereas the most common invasive technique is deep brain stimulation (DBS). In the current review, we will provide an overview of the potential of noninvasive (rTMS and tDCS) and invasive (DBS) brain stimulation techniques focusing on the treatment of mental, psychiatric, and cognitive disorders.

Neuromodulation of OCD: A review of invasive and non-invasive methods

Early research into neural correlates of obsessive compulsive disorder (OCD) has focused on individual components, several network-based models have emerged from more recent data on dysfunction within brain networks, including the the lateral orbitofrontal cortex (lOFC)-ventromedial caudate, limbic, salience, and default mode networks. Moreover, the interplay between multiple brain networks has been increasingly recognized. As the understanding of the neural circuitry underlying the pathophysiology of OCD continues to evolve, so will too our ability to specifically target these networks using invasive and noninvasive methods. This review discusses the rationale for and theory behind neuromodulation in the treatment of OCD.

Efficacy of Non-Invasive Brain Stimulation for Refractory Obsessive-Compulsive Disorder: A Meta-Analysis of Randomized Controlled Trials

Obsessive-compulsive disorder (OCD) is a neuropsychiatric disorder, with 30−40% of OCD patients being unresponsive to adequate trials of anti-OCD drugs and cognitive behavior therapy. The aim of this paper is to investigate the efficacy of non-invasive brain stimulation (NIBS) on treating refractory OCD. With PubMed, Embase, PsycInfo, and Cochrane Library used on 15 February 2022, 24 randomized controlled trials involving 663 patients were included. According to this analysis, NIBS including repetitive transcranial magnetic stimulation (rTMS), theta-burst stimulation (TBS), and transcranial direct current stimulation (tDCS), had a moderate effect on the reduction of Yale-Brown Obsessive Compulsive Scale (Y-BOCS) scores (SMD = 0.54, 95% CI: 0.26−0.81; p < 0.01). In the subgroup analysis, rTMS seemed to produce a better therapeutic effect (SMD = 0.73, 95% CI: 0.38−1.08; p < 0.01). Moreover, excitatory (SMD = 1.13, 95% CI: 0.24−2.01; p = 0.01) and inhibitory (SMD = 0.81, 95% CI: 0.26−1.36; p < 0.01) stimulation of the dorsolateral prefrontal cortex (DLPFC) both alleviated OCD symptoms. In the secondary outcome of clinical response rates, NIBS treatment led to an increase in response rates (RR = 2.26, 95% CI: 1.57−3.25; p < 0.01).

Transcranial direct current stimulation improve symptoms and modulates cortical inhibition in obsessive-compulsive disorder: A TMS-EEG study

BACKGROUND

Obsessive-compulsive disorder (OCD) is a disabling condition for which approximately 40% of patients do not respond to first-line treatment. Transcranial direct current stimulation (tDCS) is a safe and accessible technique that modulates cortical excitability and inhibition, but evidence of its efficacy for OCD is insufficient.

OBJECTIVE

To investigate the efficacy of tDCS for OCD and alterations of cortical excitability and inhibition after treatment measured by concurrent transcranial magnetic stimulation-electroencephalography (TMS-EEG).

METHODS

Twenty-four OCD patients underwent 10 20-min sessions of 1.5 mA high-definition tDCS with a cathode placed over the right orbitofrontal cortex (OFC) and anode electrodes set around the cathodal electrode. TMS-EEG was performed before and after tDCS treatment. OCD symptom severitys was assessed using Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and the Beck Depression Inventory-Ⅱ (BDI-Ⅱ), and Beck Anxiety Inventory (BAI) were used to assess the severity of depression and anxiety symptoms. Twenty-seven healthy controls were recruited with TMS-EEG recorded.

RESULTS

Following tDCS, the Y-BOCS, BDI-Ⅱ, and BAI scores decreased significantly (all p = 0.000). TMS-evoked N100 amplitude, thought to be related to GABA_B receptor function, was significantly reduced after tDCS (Z = -2.143, p = 0.032) which was higher in OCD patients than in healthy controls at baseline (Z = -2.151, p = 0.031).

LIMITATIONS

Pharmacotherapy during tDCS treatment may influence the effect of tDCS and EEG.

CONCLUSIONS

Cathodal high-definition tDCS applied over the OFC could improve OCD, depression, and anxiety symptoms along with alleviation of GABA_B receptor function.

Examining transcranial random noise stimulation as an add-on treatment for persistent symptoms in schizophrenia (STIM'Zo): a study protocol for a multicentre, double-blind, randomized sham-controlled clinical trial

Background

One out of three patients with schizophrenia failed to respond adequately to antipsychotics and continue to experience debilitating symptoms such as auditory hallucinations and negative symptoms. The development of additional therapeutic approaches for these persistent symptoms constitutes a major goal for patients. Here, we develop a randomized-controlled trial testing the efficacy of high-frequency transcranial random noise stimulation (hf-tRNS) for the treatment of resistant/persistent symptoms of schizophrenia in patients with various profiles of symptoms, cognitive deficits and illness duration. We also aim to investigate the biological and cognitive effects of hf-tRNS and to identify the predictors of clinical response.

Methods

In a randomized, double-blind, 2-arm parallel-group, controlled, multicentre study, 144 patients with schizophrenia and persistent symptoms despite the prescription of at least one antipsychotic treatment will be randomly allocated to receive either active (n = 72) or sham (n = 72) hf-tRNS. hf-tRNS (100–500 Hz) will be delivered for 20 min with a current intensity of 2 mA and a 1-mA offset twice a day on 5 consecutive weekdays. The anode will be placed over the left dorsolateral prefrontal cortex and the cathode over the left temporoparietal junction. Patients’ symptoms will be assessed prior to hf-tRNS (baseline), after the 10 sessions, and at 1-, 3- and 6-month follow-up. The primary outcome will be the number of responders defined as a reduction of at least 25% from the baseline scores on the Positive and Negative Syndrome Scale (PANSS) after the 10 sessions. Secondary outcomes will include brain activity and connectivity, source monitoring performances, social cognition, other clinical (including auditory hallucinations) and biological variables, and attitude toward treatment.

Discussion

The results of this trial will constitute a first step toward establishing the usefulness of hf-tRNS in schizophrenia whatever the stage of the illness and the level of treatment resistance. We hypothesize a long-lasting effect of active hf-tRNS on the severity of schizophrenia symptoms as compared to sham. This trial will also have implications for the use of hf-tRNS as a preventive intervention of relapse in patients with schizophrenia.

Trial registration

ClinicalTrials.gov NCT02744989. Prospectively registered on 20 April 2016

Feasibility and acceptability of transcranial stimulation in obsessive-compulsive symptoms (FEATSOCS): study protocol for a randomised controlled trial of transcranial direct current stimulation (tDCS) in obsessive-compulsive disorder (OCD)

Background

Obsessive–compulsive disorder (OCD) is a neuropsychiatric disorder which often proves refractory to current treatment approaches. Transcranial direct current stimulation (tDCS), a noninvasive form of neurostimulation, with potential for development as a self-administered intervention, has shown potential as a safe and efficacious treatment for OCD in a small number of trials. The two most promising stimulation sites are located above the orbitofrontal cortex (OFC) and the supplementary motor area (SMA).

Methods

The aim of this feasibility study is to inform the development of a definitive trial, focussing on the acceptability, safety of the intervention, feasibility of recruitment, adherence and tolerability to tDCS and study assessments and the size of the treatment effect. To this end, we will deliver a double-blind, sham-controlled, crossover randomised multicentre study in 25 adults with OCD. Each participant will receive three courses of tDCS (SMA, OFC and sham), randomly allocated and given in counterbalanced order. Each course comprises four 20-min stimulations, delivered over two consecutive days, separated by at least 4 weeks’ washout period. We will collect information about recruitment, study conduct and tDCS delivery. Blinded raters will assess clinical outcomes before, during and up to 4 weeks after stimulation using validated scales. We will include relevant objective neurocognitive tasks, testing cognitive flexibility, motor disinhibition, cooperation and habit learning.

Discussion

We will analyse the magnitude of the effect of the interventions on OCD symptoms alongside the standard deviation of the outcome measure, to estimate effect size and determine the optimal stimulation target. We will also measure the duration of the effect of stimulation, to provide information on spacing treatments efficiently. We will evaluate the usefulness and limitations of specific neurocognitive tests to determine a definitive test battery. Additionally, qualitative data will be collected from participants to better understand their experience of taking part in a tDCS intervention, as well as the impact on their overall quality of life. These clinical outcomes will enable the project team to further refine the methodology to ensure optimal efficiency in terms of both delivering and assessing the treatment in a full-scale trial.

Trial registration

ISRCTN17937049. (date applied 08/07/2019).

Recruitment (ongoing) began 23rd July 2019 and is anticipated to complete 30th April 2021.

The Involvement of the Posterior Cerebellum in Reconstructing and Predicting Social Action Sequences

Recent advances in social neuroscience have highlighted the critical role of the cerebellum and especially the posterior cerebellar Crus in social mentalizing (i.e., theory of mind). Research in the past 5 years has provided growing evidence supporting the view that the posterior cerebellum builds internal action models of our social interactions to predict how other people's actions will be executed, and what our most likely responses to these actions will be. This paper presents an overview of a series of fMRI experiments on novel tasks involving a combination of (a) the learning or generation of chronological sequences of social actions either in an explicit or implicit manner, which (b) require social mentalizing on another person's mental state such as goals, beliefs, and implied traits. Together, the results strongly confirm the central role of the posterior cerebellar Crus in identifying and automatizing action sequencing during social mentalizing, and in predicting future action sequences based on social mentalizing inferences about others. This research program has important implications: It provides for the first time (a) fruitful starting points for diagnosing and investigating social sequencing dysfunctions in a variety of mental disorders which have also been related to cerebellar dysfunctions, (b) provides the necessary tools for testing whether non-invasive neurostimulation targeting the posterior cerebellum has a causal effect on social functioning, and (c) whether these stimulation techniques and training programs guided by novel cerebellar social sequencing insights, can be exploited to increase posterior cerebellar plasticity in order to alleviate social impairments in mental disorders.

The Role of the Posterior Cerebellum in Dysfunctional Social Sequencing

Recent advances in social neuroscience have highlighted the critical role of the cerebellum in social cognition, and especially the posterior cerebellum. Studies have supported the view that the posterior cerebellum builds internal action models of our social interactions to predict how other people's actions will be executed and what our most likely responses are to these actions. This mechanism allows to better anticipate action sequences during social interactions in an automatic and intuitive way and to fine-tune these anticipations, making it easier to understand other's social behaviors and mental states (e.g., beliefs, intentions, traits). In this paper, we argue that the central role of the posterior cerebellum in identifying and automatizing social action sequencing provides a fruitful starting point for investigating social dysfunctions in a variety of clinical pathologies, such as autism, obsessive-compulsive and bipolar disorder, depression, and addiction. Our key hypothesis is that dysfunctions of the posterior cerebellum lead to under- or overuse of inflexible social routines and lack of plasticity for learning new, more adaptive, social automatisms. We briefly review past research supporting this view and propose a program of research to test our hypothesis. This approach might alleviate a variety of mental problems of individuals who suffer from inflexible automatizations that stand in the way of adjustable and intuitive social behavior, by increasing posterior cerebellar plasticity using noninvasive neurostimulation or neuro-guided training programs.

Therapeutic Neurostimulation in Obsessive-Compulsive and Related Disorders: A Systematic Review

Invasive and noninvasive neurostimulation therapies for obsessive-compulsive and related disorders (OCRD) were systematically reviewed with the aim of assessing clinical characteristics, methodologies, neuroanatomical substrates, and varied stimulation parameters. Previous reviews have focused on a narrow scope, statistical rather than clinical significance, grouped together heterogenous protocols, and proposed inconclusive outcomes and directions. Herein, a comprehensive and transdiagnostic evaluation of all clinically relevant determinants is presented with translational clinical recommendations and novel response rates. Electroconvulsive therapy (ECT) studies were limited in number and quality but demonstrated greater efficacy than previously identified. Targeting the pre-SMA/SMA is recommended for transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS). TMS yielded superior outcomes, although polarity findings were conflicting, and refinement of frontal/cognitive control protocols may optimize outcomes. For both techniques, standardization of polarity, more treatment sessions (>20), and targeting multiple structures are encouraged. A deep brain stimulation (DBS) 'sweet spot' of the striatum for OCD was proposed, and CBT is strongly encouraged. Tourette's patients showed less variance and reliance on treatment optimization. Several DBS targets achieved consistent, rapid, and sustained clinical response. Analysis of fiber connectivity, as opposed to precise neural regions, should be implemented for target selection. Standardization of protocols is necessary to achieve translational outcomes.

Multifocal stimulation of the cerebro-cerebellar loop during the acquisition of a novel motor skill

Transcranial direct current stimulation (tDCS)-based interventions for augmenting motor learning are gaining interest in systems neuroscience and clinical research. Current approaches focus largely on monofocal motorcortical stimulation. Innovative stimulation protocols, accounting for motor learning related brain network interactions also, may further enhance effect sizes. Here, we tested different stimulation approaches targeting the cerebro-cerebellar loop. Forty young, healthy participants trained a fine motor skill with concurrent tDCS in four sessions over two days, testing the following conditions: (1) monofocal motorcortical, (2) sham, (3) monofocal cerebellar, or (4) sequential multifocal motorcortico-cerebellar stimulation in a double-blind, parallel design. Skill retention was assessed after circa 10 and 20 days. Furthermore, potential underlying mechanisms were studied, applying paired-pulse transcranial magnetic stimulation and multimodal magnetic resonance imaging-based techniques. Multisession motorcortical stimulation facilitated skill acquisition, when compared with sham. The data failed to reveal beneficial effects of monofocal cerebellar or additive effects of sequential multifocal motorcortico-cerebellar stimulation. Multimodal multiple linear regression modelling identified baseline task performance and structural integrity of the bilateral superior cerebellar peduncle as the most influential predictors for training success. Multisession application of motorcortical tDCS in several daily sessions may further boost motor training efficiency. This has potential implications for future rehabilitation trials.

Treatment effect variability in brain stimulation across psychiatric disorders: A meta-analysis of variance

Noninvasive brain stimulation methods such as transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are promising add-on treatments for a number of psychiatric conditions. Yet, some of the initial excitement is wearing off. Randomized controlled trials (RCT) have found inconsistent results. This inconsistency is suspected to be the consequence of variation in treatment effects and solvable by identifying responders in RCTs and individualizing treatment. However, is there enough evidence from RCTs that patients respond differently to treatment? This question can be addressed by comparing the variability in the active stimulation group with the variability in the sham group. We searched MEDLINE/PubMed and included all double-blinded, sham-controlled RCTs and crossover trials that used TMS or tDCS in adults with a unipolar or bipolar depression, bipolar disorder, schizophrenia spectrum disorder, or obsessive compulsive disorder. In accordance with the PRISMA guidelines to ensure data quality and validity, we extracted a measure of variability of the primary outcome. A total of 130 studies with 5748 patients were considered in the analysis. We calculated variance-weighted variability ratios for each comparison of active stimulation vs sham and entered them into a random-effects model. We hypothesized that treatment effect variability in TMS or tDCS would be reflected by increased variability after active compared with sham stimulation, or in other words, a variability ratio greater than one. Across diagnoses, we found only a minimal increase in variability after active stimulation compared with sham that did not reach statistical significance (variability ratio = 1.03; 95% CI, 0.97, 1.08, P = 0.358). In conclusion, this study found little evidence for treatment effect variability in brain stimulation, suggesting that the need for personalized or stratified medicine is still an open question.

The safety and efficacy of transcranial direct current stimulation as add-on therapy to fluoxetine in obsessive-compulsive disorder: a randomized, double-blind, sham-controlled, clinical trial

BACKGROUND

Obsessive-compulsive disorder (OCD) is an anxiety disorder that causes impairment in daily activities. This study aimed to assess the safety and efficacy of transcranial direct current stimulation (tDCS) as adjunctive therapy with fluoxetine in individuals diagnosed with moderate to severe OCD.

METHODS

This is a randomized, double-blind sham-controlled trial. Individuals with OCD who had baseline Yale-Brown obsessive-compulsive scale (Y-BOCS) of > 15 were enrolled. Eligible cases were randomly assigned in 1:1 ratio to receive either 20-min-period of stimulation with tDCS and fluoxetine (experimental arm) or fluoxetine only (sham control arm). The anodal electrode of tDCS was placed over the left dorsolateral prefrontal cortex (Fp3) and the cathodal electrode was placed over the right orbitofrontal cortex (F8). Two mA electrical stimulation with the tDCS was used for 20 min in individuals of experimental group. In the control group, electrodes were placed and stimulation was administered for 30 s to induce the same skin sensation as in experimental group. This procedure was performed three times per week for 8 weeks. Y-BOCS test was assessed at baseline, week 4 (after 12th stimulation), week 8 (after 24th stimulation), and 1 month after the last stimulation. The primary endpoints were the mean changes in Y-BOCS total score from baseline to the last visit. The secondary endpoints were the mean changes in obsession and compulsion sub-scores from baseline to the last visit. Adverse events were also assessed. Mixed design repeated measures analysis of variance assessed the endpoints.

RESULTS

Sixty individuals (30 in each group) were participated. All individuals in control group and 28 cases in experimental arm completed the trial. The mean Y-BOCS (F(1.85) = 30.83; P < 0.001), OCD obsession (F(2.23) = 25.01; P < 0.001), and compulsion (F(2.06) = 10.81; P < 0.001) scores decreased significantly during the study. No statistical differences were, however, detected between experimental and control groups (P > 0.05). The tDCS was well tolerated and no major adverse events were reported.

CONCLUSION

This study showed that among individuals with moderate to severe OCD, there was no significant difference regarding OC symptoms between cases used tDCS as adjunctive therapy with fluoxetine and individuals used fluoxetine only.

TRIAL REGISTRATION

IRCT2017030632904N1 . Registered 14 July 2017, http://irct.ir/user/trial/44193/view.

Treating refractory obsessive-compulsive disorder with transcranial direct current stimulation: An open label study

BACKGROUND

Obsessive-compulsive disorder (OCD) is a complex disorder with 40%-60% of patients' refractory to treatment. Transcranial direct current stimulation (tDCS) has been shown to induce potent and long-lasting effects on cortical excitability. The aim of the present clinical trial was to evaluate the therapeutic efficacy and tolerability of cathodal tDCS over the supplementary motor area (SMA) in treatment-resistant OCD patients.

METHODS

Twenty-one treatment-resistant OCD outpatients received 10 sessions of tDCS. Each treatment session consisted of 2 mA stimuli for 30 min. The cathode was positioned over the bilateral SMA and the anode over the right supraorbital area. Patients were evaluated at baseline, end of treatment, one-month follow-up, and three-month follow-up. Response to treatment was defined as at least a decrease of 35% on the Yale-Brown Obsessive-Compulsive Scale (YBOCS) and a score of 2 or less on the Clinical Global Impressions-Improvement (CGI-I) between baseline and 1-month follow-up.

RESULTS

There was a significant decrease of YBOCS scores between baseline and one-month assessment. At one month, five patients (24%) were considered as responders and 3 (15%) at 3 months. We also observed concomitant changes in depressive symptoms, and insight. The treatment was well tolerated. Short-lasting side effects were reported as localized tingling sensation and skin redness.

CONCLUSION

Our results suggest that the use of cathodal tDCS over the SMA and anodal tDCS over the right supraorbital area in OCD treatment-refractory patients is safe and promising to improve obsessive and compulsive symptoms. Large randomized controlled trials are needed to confirm this positive result.

Could Transcranial Direct Current Stimulation Join the Therapeutic Armamentarium in Obsessive-Compulsive Disorder?

Obsessive-compulsive disorder (OCD) is a mental disorder that can affect around 1-3% of individuals [...].