A Clinical Trial with Combined Transcranial Direct Current Stimulation and Attentional Bias Modification in Alcohol-Dependent Patients

A systematic review and meta-analysis of neuromodulation therapies for substance use disorders

While pharmacological, behavioral and psychosocial treatments are available for substance use disorders (SUDs), they are not always effective or well-tolerated. Neuromodulation (NM) methods, including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS) and deep brain stimulation (DBS) may address SUDs by targeting addiction neurocircuitry. We evaluated the efficacy of NM to improve behavioral outcomes in SUDs. A systematic literature search was performed on MEDLINE, PsychINFO, and PubMed databases and a list of search terms for four key concepts (SUD, rTMS, tDCS, DBS) was applied. Ninety-four studies were identified that examined the effects of rTMS, tDCS, and DBS on substance use outcomes (e.g., craving, consumption, and relapse) amongst individuals with SUDs including alcohol, tobacco, cannabis, stimulants, and opioids. Meta-analyses were performed for alcohol and tobacco studies using rTMS and tDCS. We found that rTMS reduced substance use and craving, as indicated by medium to large effect sizes (Hedge's g > 0.5). Results were most encouraging when multiple stimulation sessions were applied, and the left dorsolateral prefrontal cortex (DLPFC) was targeted. tDCS also produced medium effect sizes for drug use and craving, though they were highly variable and less robust than rTMS; right anodal DLPFC stimulation appeared to be most efficacious. DBS studies were typically small, uncontrolled studies, but showed promise in reducing misuse of multiple substances. NM may be promising for the treatment of SUDs. Future studies should determine underlying neural mechanisms of NM, and further evaluate extended treatment durations, accelerated administration protocols and long-term outcomes with biochemical verification of substance use.

No time to lose: the current state of research in rapid-acting psychotherapeutics

The vast majority of treatments for psychiatric and substance use disorders take weeks to work. Notable exceptions to this rule exist, with some treatments such as intravenous ketamine resolving symptoms in minutes to hours. Current research is focused on identifying novel approaches to rapid-acting psychotherapeutics. Promising results from studies of novel classes of drugs and innovative brain stimulation therapies are currently being studied through both clinical and pre-clinical research, as described here. Research focused on understanding neurobiological mechanisms, effective therapeutic context, and implementation approaches are needed to maximize the potential reach of these therapies.

Craving modulates attentional bias towards alcohol in severe alcohol use disorder: An eye-tracking study

BACKGROUND AND AIMS

Competing models disagree on three theoretical questions regarding alcohol-related attentional bias (AB), a key process in severe alcohol use disorder (SAUD): (1) is AB more of a trait (fixed, associated with alcohol use severity) or state (fluid, associated with momentary craving states) characteristic of SAUD; (2) does AB purely reflect the over-activation of the reflexive/reward system or is it also influenced by the activity of the reflective/control system and (3) does AB rely upon early or later processing stages? We addressed these issues by investigating the time-course of AB and its modulation by subjective craving and cognitive load in SAUD.

DESIGN

A free-viewing eye-tracking task, presenting pictures of alcoholic and non-alcoholic beverages, combined with a concurrent cognitive task with three difficulty levels.

SETTING

A laboratory setting in the detoxification units of three Belgian hospitals.

PARTICIPANTS

We included 30 patients with SAUD self-reporting craving at testing time, 30 patients with SAUD reporting a total absence of craving and 30 controls matched on sex and age. All participants from SAUD groups met the DSM-5 criteria for SAUD.

MEASUREMENTS

We assessed AB through early and late eye-tracking indices. We evaluated the modulation of AB by craving (comparison between patients with/without craving) and cognitive load (variation of AB with the difficulty level of the concurrent task).

FINDINGS

Dwell time measure indicated that SAUD patients with craving allocated more attention towards alcohol-related stimuli than patients without craving (P < 0.001, d = 1.093), resulting in opposite approach/avoidance AB according to craving presence/absence. SAUD patients without craving showed a stronger avoidance AB than controls (P = 0.003, d = 0.806). AB did not vary according to cognitive load (P = 0.962, η2 p  = 0.004).

CONCLUSIONS

The direction of alcohol-related attentional bias (approach/avoidance) appears to be determined by patients' subjective craving at testing time and does not function as a stable trait of severe alcohol use disorder. Alcohol-related attentional bias appears to rely on later/controlled attentional stages but is not modulated by the saturation of the reflective/control system.

Targeting cravings in substance addiction with transcranial direct current stimulation: insights from a meta-analysis of sham-controlled trials

Addiction is a substantial health concern; craving-the core symptom of addiction-is strongly associated with relapse. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that reduces cravings by altering cortical excitability and connectivity in brain regions. This systematic review and meta-analysis was conducted (following the PRISMA guidelines) to evaluate the efficacy of tDCS in reducing cravings for substances. Our analysis included 43 randomized, sham-controlled trials involving 1,095 and 913 participants receiving tDCS and sham stimulation, respectively. We analyzed the changes in craving scores and found that tDCS led to a moderate reduction in cravings compared with the sham effects. This effect was particularly pronounced when bilateral stimulation was used, the anodal electrode was placed on the right dorsolateral prefrontal cortex, current intensities ranged from 1.5 to 2 mA, stimulation sessions lasted 20 minutes, and the electrodes size was ≥35 cm². Notably, tDCS effectively reduced cravings for opioids, methamphetamine, cocaine, and tobacco but not for alcohol or cannabis. Our findings indicate tDCS as a promising, noninvasive, and low-risk intervention for reducing cravings for opioids, methamphetamine, cocaine, and tobacco. Additional studies are warranted to refine stimulation parameters and evaluate the long-term efficacy of tDCS in managing substance cravings.

Approach-Bias Retraining and Other Training Interventions as Add-On in the Treatment of AUD Patients

In the past two decades, a variety of cognitive training interventions have been developed to help people overcome their addictive behaviors. Conceptually, it is important to distinguish between programs in which reactions to addiction-relevant cues are trained (varieties of cognitive bias modification, CBM) and programs in which general abilities are trained such as working memory or mindfulness. CBM was first developed to study the hypothesized causal role in mental disorders: by directly manipulating the bias, it was investigated to what extent this influenced disorder-relevant behavior. In these proof-of-principle studies, the bias was temporarily modified in volunteers, either temporarily increased or decreased, with corresponding effects on behavior (e.g., beer consumption), in case the bias was successfully manipulated. In subsequent clinical randomized controlled trials (RCTs), training (away from the substance vs. sham training) was added to clinical treatment. These studies have demonstrated that CBM, as added to treatment, reduces relapse with a small effect of about 10% (similar effect size as for medication, with the strongest evidence for approach-bias modification). This has not been found for general ability training (e.g., working memory training), although effects on other psychological functions have been found (e.g., impulsivity). Mindfulness also has been found to help people overcome addictions, and different from CBM, also as stand-alone intervention. Research on (neuro-)cognitive mechanisms underlying approach-bias modification has pointed to a new perspective in which automatic inferences rather than associations are influenced by training, which has led to the development of a new variety of training: ABC training.

Alcohol-specific inhibition training in patients with alcohol use disorder: a multi-centre, double-blind randomized clinical trial examining drinking outcome and working mechanisms

AIMS

For the first time, to our knowledge, in a clinical sample with alcohol use disorder (AUD), this study compared the effects of two versions of alcohol-specific inhibition training (Alc-IT) on drinking outcomes and on experimental parameters assessing two possible working mechanisms: stimulus devaluation and inhibitory enhancement.

DESIGN

Multi-centre, double-blind, three-arm clinical RCT with 3-, 6- and 12-month follow-up comparing standard Alc-IT, improved Alc-IT and an active control condition.

SETTING

Three specialized AUD treatment centres in Switzerland.

PARTICIPANTS

A total of 242 detoxified, recently abstinent patients with severe AUD (18-60 years; 29.8% female).

INTERVENTION AND COMPARATOR

Both interventions [standard Alc-IT (n = 84) and improved Alc-IT (n = 79)] and the comparator [unspecific inhibition training (n = 79)] consisted of six sessions of a modified inhibitory task (Go/NoGo task) with alcohol-related and neutral stimuli. Both versions of Alc-IT required response inhibition in alcohol-related trials but differed in Go/NoGo ratios (standard: 50/50; improved: 75/25), with improved Alc-IT posing higher inhibitory demands. The control condition, an unspecific inhibition training, featured alcohol-related pictures in Go as well as NoGo trials.

MEASUREMENTS

The primary outcome, percentage of days abstinent, was assessed at 3-month follow-up with a time-line follow-back interview.

FINDINGS

The group receiving improved Alc-IT showed a significantly higher percentage of days abstinent at 3-month follow-up compared with the control group [γ_control  = 74.30; γ_improved  = 85.78; β = 11.48, 95% confidence interval (CI) = 2.57, 20.40, P = 0.012, adjusted r²  = 0.062], while for standard Alc-IT no effect significantly different from zero was detected (γ_standard  = 70.95; β = -3.35, 95% CI = -12.20, 5.50, P = 0.457, adjusted r²  = -0.04).

CONCLUSIONS

Alcohol-specific inhibition training with high inhibitory demands increased days abstinent at 3-month follow-up in patients with severe alcohol use disorder. Such an improved, inhibitory-demanding, alcohol-specific inhibition training outperformed the standard version of alcohol-specific inhibition training, suggesting an inhibitory working mechanism.

A critical perspective on updating drug memories through the integration of memory editing and brain stimulation

Addiction is a persistent, recurring condition characterized by repeated relapses despite the desire to control drug use or maintain sobriety. The attainment of abstinence is hindered by persistent maladaptive drug-associated memories, which drive drug-seeking and use behavior. This article examines the preliminary evidence supporting the combination of non-invasive brain stimulation (NIBS) techniques and memory editing (or reconsolidation) interventions as add-on forms of treatment for individuals with substance-related disorders (SUD). Studies have shown that NIBS can modestly reduce drug use and craving through improved cognitive control or other undetermined reasons. Memory reconsolidation, a process by which a previously consolidated memory trace can be made labile again, can potentially erase or significantly weaken SUD memories underpinning craving and the propensity for relapse. This approach conveys enthusiasm while also emphasizing the importance of managing boundary conditions and null results for interventions found on fear memory reconsolidation. Recent studies, which align with the state-dependency and activity-selectivity hypotheses, have shown that the combination of NIBS and behavioral interventions holds promise for treating SUD by reducing self-reported and physiological aspects of craving. Effective long-term outcomes for this procedure require better identification of critical memories, a deeper understanding of the brain mechanisms underlying SUD and memory reconsolidation and overcoming any boundary conditions of destabilized memories. This will enable the procedure to be personalized to the unique needs of individual patients.

The Treatment of Substance Use Disorders: Recent Developments and New Perspectives

Substance-related disorders are complex psychiatric disorders that are characterized by continued consumption in spite of harmful consequences. Addiction affects various brain networks critically involved in learning, reward, and motivation, as well as inhibitory control. Currently applied therapeutic approaches aim at modification of behavior that ultimately leads to decrease of consumption or abstinence in individuals with substance use disorders. However, traditional treatment methods might benefit from recent neurobiological and cognitive neuroscientific research findings. Novel cognitive-behavioral approaches in the treatment of addictive behavior aim at enhancement of strategies to cope with stressful conditions as well as craving-inducing cues and target erroneous learning mechanisms, including cognitive bias modification, reconsolidation-based interventions, mindfulness-based interventions, virtual-reality-based cue exposure therapy as well as pharmacological augmentation strategies. This review discusses therapeutic strategies that target dysregulated neurocognitive processes associated with the development and maintenance of disordered substance use and may hold promise as effective treatments for substance-related disorders.

Boosting psychological change: Combining non-invasive brain stimulation with psychotherapy

Mental health disorders and substance use disorders are a leading cause of morbidity and mortality worldwide, and one of the most important challenges for public health systems. While evidence-based psychotherapy is generally pursued to address mental health challenges, psychological change is often hampered by non-adherence to treatments, relapses, and practical barriers (e.g., time, cost). In recent decades, Non-invasive brain stimulation (NIBS) techniques have emerged as promising tools to directly target dysfunctional neural circuitry and promote long-lasting plastic changes. While the therapeutic efficacy of NIBS protocols for mental illnesses has been established, neuromodulatory interventions might also be employed to support the processes activated by psychotherapy. Indeed, combining psychotherapy with NIBS might help tailor the treatment to the patient's unique characteristics and therapeutic goal, and would allow more direct control of the neuronal changes induced by therapy. Herein, we overview emerging evidence on the use of NIBS to enhance the psychotherapeutic effect, while highlighting the next steps in advancing clinical and research methods toward personalized intervention approaches.

Forgetting Alcohol: A Double-Blind, Randomized Controlled Trial Investigating Memory Inhibition Training in Young Binge Drinkers

Background

Binge Drinking (BD) has been associated with altered inhibitory control and augmented alcohol-cue reactivity. Memory inhibition (MI), the ability to voluntarily suppress unwanted thoughts/memories, may lead to forgetting of memories in several psychiatric conditions. However, despite its potential clinical implications, no study to date has explored the MI abilities in populations with substance misuse, such as binge drinkers (BDs).

Method

This study—registered in the NIH Clinical Trials Database (ClinicalTrials.gov identifier: NCT05237414)—aims firstly to examine the behavioral and electroencephalographic (EEG) correlates of MI among college BDs. For this purpose, 45 BDs and 45 age-matched non/low-drinkers (50% female) will be assessed by EEG while performing the Think/No-Think Alcohol task, a paradigm that evaluates alcohol-related MI. Additionally, this work aims to evaluate an alcohol-specific MI intervention protocol using cognitive training (CT) and transcranial direct current stimulation (tDCS) while its effects on behavioral and EEG outcomes are assessed. BDs will be randomly assigned to one MI training group: combined [CT and verum tDCS applied over the right dorsolateral prefrontal cortex (DLPFC)], cognitive (CT and sham tDCS), or control (sham CT and sham tDCS). Training will occur in three consecutive days, in three sessions. MI will be re-assessed in BDs through a post-training EEG assessment. Alcohol use and craving will be measured at the first EEG assessment, and both 10-days and 3-months post-training. In addition, behavioral and EEG data will be collected during the performance of an alcohol cue reactivity (ACR) task, which evaluates attentional bias toward alcoholic stimuli, before, and after the MI training sessions.

Discussion

This study protocol will provide the first behavioral and neurofunctional MI assessment in BDs. Along with poor MI abilities, BDs are expected to show alterations in event-related potentials and functional connectivity patterns associated with MI. Results should also demonstrate the effectiveness of the protocol, with BDs exhibiting an improved capacity to suppress alcohol-related memories after both combined and cognitive training, along with a reduction in alcohol use and craving in the short/medium-term. Collectively, these findings might have major implications for the understanding and treatment of alcohol misuse.

Clinical Trial Registration

[www.ClinicalTrials.gov], identifier [NCT05237414].

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.

How Should Transcranial Direct Current Stimulation be Used in Populations With Severe Alcohol Use Disorder? A Clinically Oriented Systematic Review

Background and rationale. Severe alcohol use disorder (SAUD) is a major public health concern, given its massive individual, interpersonal, and societal consequences. The available prevention and treatment programs have proven limited effectiveness, as relapse rates are still high in this clinical population. Developing effective interventions reducing the appearance and persistence of SAUD thus constitutes an experimental and clinical priority. Among the new therapeutic approaches, there is a growing interest for noninvasive neuromodulation techniques, and particularly for transcranial direct current stimulation (tDCS) as an adjunctive treatment in neuropsychiatric disorders, including SAUD. Methods. We propose a systematic review, based on preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines, evaluating the available evidence on the effectiveness of tDCS to improve clinical interventions in SAUD. Results. We provide an integrative overview of studies applying tDCS in clinical populations with SAUD, together with a standardized methodological quality assessment. We show that the currently available data remain inconsistent. Some data suggested that tDCS can (1) reduce craving, relapse or alcohol-cue reactivity and (2) improve cognitive control and inhibition. However, other studies did not observe any beneficial effect of tDCS in SAUD. Conclusions. Capitalizing on the identified strengths and shortcomings of available results, we present evidence-based clinical guidelines to integrate tDCS in current clinical settings and to combine it with neurocognitive training.

Attentional bias in alcohol drinkers: A systematic review of its link with consumption variables

In severe alcohol use disorder (SAUD), attentional bias refers to the preferential allocation of attentional resources toward alcohol-related cues. Dominant models consider that this bias plays a key role in the emergence and maintenance of SAUD. We evaluate the available experimental support for this assumption through a systematic literature review, providing a critical synthesis of studies exploring the links between alcohol consumption and attentional bias. Using PRISMA guidelines, we explored three databases (PsycINFO, PubMed, Scopus) and extracted 95 papers. We assessed their methodological quality and categorized them based on the population targeted, namely patients with SAUD or subclinical populations with various drinking patterns. We also classified papers according to the measures used (i.e., behavioral or eye-tracking measures). Overall, subclinical populations present an alcohol-related bias, but many studies in SAUD did not find such bias, nor approach/avoidance patterns. Moreover, attentional bias fluctuates alongside motivational states rather than according to alcohol use severity, which questions its stability. We provide recommendations to develop further theoretical knowledge and overcome methodological shortcomings.

State-dependent effects of neural stimulation on brain function and cognition

Invasive and non-invasive brain stimulation methods are widely used in neuroscience to establish causal relationships between distinct brain regions and the sensory, cognitive and motor functions they subserve. When combined with concurrent brain imaging, such stimulation methods can reveal patterns of neuronal activity responsible for regulating simple and complex behaviours at the level of local circuits and across widespread networks. Understanding how fluctuations in physiological states and task demands might influence the effects of brain stimulation on neural activity and behaviour is at the heart of how we use these tools to understand cognition. Here we review the concept of such 'state-dependent' changes in brain activity in response to neural stimulation, and consider examples from research on altered states of consciousness (for example, sleep and anaesthesia) and from task-based manipulations of selective attention and working memory. We relate relevant findings from non-invasive methods used in humans to those obtained from direct electrical and optogenetic stimulation of neuronal ensembles in animal models. Given the widespread use of brain stimulation as a research tool in the laboratory and as a means of augmenting or restoring brain function, consideration of the influence of changing physiological and cognitive states is crucial for increasing the reliability of these interventions.

Mini-review: When neurostimulation joins cognitive-behavioral therapy. On the need of combining evidence-based treatments for addiction disorders

Substance and behavioral addiction is a global health problem related to cognitive functioning and emotional responses like top-down control and craving. The present review discusses the role of non-invasive brain stimulation (NIBS) and cognitive-behavioral therapy (CBT) as evidence-based treatments for addiction disorders. The discussion spans between several evidence for both therapies, also considering the difference and heterogeneity among clinical protocols. Nowadays, literature is consistent in indicating the neurostimulation of the prefrontal cortex as effective for different kinds of addiction, corroborating the evidence that they rely on a common network in the brain. Likewise, within the CBT studies it is possible to observe a wide range of interventions that are overall effective in regulating the executive functions associated with addiction disorders. Nevertheless, the integration of NIBS and CBT in addictions has been scarcely considered in literature so far. For this reason, the present article is meant to foster empirical research in this field by highlighting the findings supporting these evidence-based interventions, both as stand-alone and integrated treatments. To this aim, psychological and neurophysiological mechanisms of NIBS and CBT in addictions are reviewed, and the rationale of their integration discussed. In particular, as evidence suggest these treatments affect top-down and bottom-up processes in different ways, with NIBS reducing craving and CBT boosting motivation and coping, we suggest their combination might better target the different components of addiction to promote abstinence.

Transcranial direct current stimulation (tDCS) reduces motivation to drink ethanol and reacquisition of ethanol self-administration in female mice

Transcranial direct current stimulation (tDCS) is an emerging noninvasive brain neuromodulation technique aimed at relieving symptoms associated with psychiatric disorders, including addiction. The goal of the present study was to better identify which phase of alcohol-related behavior (hedonic effect, behavioral sensitization, self-administration, or motivation to obtain the drug) might be modulated by repeated anodal tDCS over the frontal cortex (0.2 mA, 20 min, twice a day for 5 consecutive days), using female mice as a model. Our data showed that tDCS did not modulate the hedonic effects of ethanol as assessed by a conditioned place preference test (CPP) or the expression of ethanol-induced behavioral sensitization. Interestingly, tDCS robustly reduced reacquisition of ethanol consumption (50% decrease) following extinction of self-administration in an operant paradigm. Furthermore, tDCS significantly decreased motivation to drink ethanol on a progressive ratio schedule (30% decrease). Taken together, our results show a dissociation between the effects of tDCS on “liking” (hedonic aspect; no effect in the CPP) and “wanting” (motivation; decreased consumption on a progressive ratio schedule). Our tDCS procedure in rodents will allow us to better understand its mechanisms of action in order to accelerate its use as a complementary and innovative tool to help alcohol-dependent patients maintain abstinence or reduce ethanol intake.

Neurobiological mechanisms of control in alcohol use disorder - moving towards mechanism-based non-invasive brain stimulation treatments

Alcohol use disorder (AUD) is characterized by excessive habitual drinking and loss of control over alcohol intake despite negative consequences. Both of these aspects foster uncontrolled drinking and high relapse rates in AUD patients. Yet, common interventions mostly focus on the phenomenological level, and prioritize the reduction of craving and withdrawal symptoms. Our review provides a mechanistic understanding of AUD and suggests alternative therapeutic approaches targeting the mechanisms underlying dysfunctional alcohol-related behaviours. Specifically, we explain how repeated drinking fosters the development of rigid drinking habits and is associated with diminished cognitive control. These behavioural and cognitive effects are then functionally related to the neurobiochemical effects of alcohol abuse. We further explain how alterations in fronto-striatal network activity may constitute the neurobiological correlates of these alcohol-related dysfunctions. Finally, we discuss limitations in current pharmacological AUD therapies and suggest non-invasive brain stimulation (like TMS and tDCS interventions) as a potential addition/alternative for modulating the activation of both cortical and subcortical areas to help re-establish the functional balance between controlled and automatic behaviour.

Modulation of the cognitive event-related potential P3 by transcranial direct current stimulation: Systematic review and meta-analysis

Transcranial direct current stimulation (tDCS) has been widely used to modulate cognition and behavior. However, only a few studies have been probing the brain mechanism underlying the effects of tDCS on cognitive processing, especially throughout electrophysiological markers, such as the P3. This meta-analysis assessed the effects of tDCS in P3 amplitude and latency during an oddball, n-back, and Go/No-Go tasks, as well as during emotional processing. A total of 36 studies were identified, but only 23 were included in the quantitative analysis. The results show that the parietal P3 amplitude increased during oddball and n-back tasks, mostly after anodal stimulation over the left dorsolateral prefrontal cortex (p = 0.018, SMD = 0.4) and right inferior frontal gyrus (p < 0.001, SMD = 0.669) respectively. These findings suggest the potential usefulness of the parietal P3 ERP as a marker of tDCS-induced effects during task performance. Nonetheless, this study had a low number of studies and the presence of considerable risk of bias, highlighting issues to be addressed in the future.

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.

Modulation of Methamphetamine-Related Attention Bias by Intermittent Theta-Burst Stimulation on Left Dorsolateral Prefrontal Cortex

Background

Previous studies have identified the treatment effect of repetitive transcranial magnetic stimulation (rTMS) on cravings of patients with methamphetamine use disorder (MUD). However, the mechanism underlying the treatment effect remains largely unknown. A potential candidate mechanism could be that rTMS over the dorsolateral prefrontal cortex (DLPFC) modulates the attention bias to methamphetamine-related cues. The purpose of this study is therefore to determine the modulation of rTMS on methamphetamine-related attention bias and the corresponding electrophysiological changes.

Methods

Forty-nine patients with severe MUD were included for analysis. The subjects were randomized to receive the active intermittent theta-burst stimulation (iTBS) or sham iTBS targeting DLPFC for 20 sessions. Participants performed the Addiction Stroop Task before and after the treatment while being recorded by a 64-channel electroencephalogram. Baseline characteristics were collected through the Addiction Severity Index.

Results

Post-treatment evaluations showed a reduced error rate in discriminating the color of methamphetamine words in the active iTBS group compared with the sham iTBS group. Following rTMS treatment, we found the significant time-by-group effect for the N1 amplitude (methamphetamine words > neutral words) and P3 latency (methamphetamine words > neutral words). The change of N1 amplitude was positively correlated with cravings in the active group. Moreover, reduced power of neural oscillation in the beta band, manifesting at frontal central areas, was also found in the active group.

Conclusion

This study suggests that attention bias and the beta oscillation during the attentional processing of methamphetamine words in patients with MUD could be modulated by iTBS applied to left DLPFC.

Bilateral transcranial direct current stimulation attenuated symptoms of alcohol use disorder: A systematic review and meta-analysis

BACKGROUND

Alcohol use disorder is one of the common substance use disorders leading to mental and health problems. Despite the potential positive effects of transcranial direct current stimulation (tDCS) on symptoms of various substance use disorder, how specific tDCS protocols effectively influence on individuals with alcohol use disorder is still controversial. This systematic review and meta-analysis investigated beneficial effects of tDCS on symptoms of alcohol use disorder.

METHOD

Eighteen total studies met our inclusion criteria, and we used 25 total comparisons from the qualified studies for the data synthesis. We estimated effect sizes by quantifying changes in alcohol craving and consumption between active tDCS protocol and sham groups. In addition, three moderator variable analyses determined whether tDCS effects on symptoms of alcohol use disorder were different based on (a) bilateral versus unilateral tDCS protocols, (b) specific targeted regions, and (c) multiple sessions versus single session of tDCS protocols.

RESULTS

Random-effects model meta-analysis revealed small positive tDCS effects on alcohol craving and consumption. Specifically, bilateral tDCS protocols significantly reduced alcohol craving, and further anodal tDCS on right dorsolateral prefrontal cortex (DLPFC) and cathodal tDCS on left DLPFC revealed significant positive effects. The multiple sessions of tDCS protocols showed better effects on reducing alcohol craving.

CONCLUSIONS

The current findings suggested that bilateral tDCS protocols including anodal tDCS on right DLPFC and cathodal tDCS on left DLPFC with multiple sessions may effectively improve tDCS effects on symptoms of alcohol use disorder.

Transcranial Direct Current Stimulation (tDCS) Augments the Effects of Gamified, Mobile Attention Bias Modification

Anxiety-related attention bias (AB) is the preferential processing of threat observed in clinical and sub-clinical anxiety. Attention bias modification training (ABMT) is a computerized cognitive training technique designed to systematically direct attention away from threat and ameliorate AB, but mixed and null findings have highlighted gaps in our understanding of mechanisms underlying ABMT and how to design the most effective delivery systems. One neuromodulation technique, transcranial direct current stimulation (tDCS) across the pre-frontal cortex (PFC) may augment the effects of ABMT by strengthening top-down cognitive control processes, but the evidence base is limited and has not been generalized to current approaches in digital therapeutics, such as mobile applications. The present study was a single-blind randomized sham-controlled design. We tested whether tDCS across the PFC, vs. sham stimulation, effectively augments the beneficial effects of a gamified ABMT mobile app. Thirty-eight adults (Mage = 23.92, SD = 4.75; 18 females) evidencing low-to-moderate anxiety symptoms were randomly assigned to active or sham tDCS for 30-min while receiving ABMT via a mobile app. Participants reported on potential moderators of ABMT, including life stress and trait anxiety. ECG was recorded during a subsequent stressor to generate respiratory sinus arrhythmia (RSA) suppression as a metric of stress resilience. ABMT delivered via the app combined with tDCS (compared to sham) reduced AB and boosted stress resilience measured via RSA suppression, particularly for those reporting low life stress. Our results integrating tDCS with ABMT provide insight into the mechanisms of AB modulation and support ongoing evaluations of enhanced ABMT reliability and effectiveness via tDCS.

Evidence-Based Guidelines and Secondary Meta-Analysis for the Use of Transcranial Direct Current Stimulation in Neurological and Psychiatric Disorders

BACKGROUND

Transcranial direct current stimulation has shown promising clinical results, leading to increased demand for an evidence-based review on its clinical effects.

OBJECTIVE

We convened a team of transcranial direct current stimulation experts to conduct a systematic review of clinical trials with more than 1 session of stimulation testing: pain, Parkinson's disease motor function and cognition, stroke motor function and language, epilepsy, major depressive disorder, obsessive compulsive disorder, Tourette syndrome, schizophrenia, and drug addiction.

METHODS

Experts were asked to conduct this systematic review according to the search methodology from PRISMA guidelines. Recommendations on efficacy were categorized into Levels A (definitely effective), B (probably effective), C (possibly effective), or no recommendation. We assessed risk of bias for all included studies to confirm whether results were driven by potentially biased studies.

RESULTS

Although most of the clinical trials have been designed as proof-of-concept trials, some of the indications analyzed in this review can be considered as definitely effective (Level A), such as depression, and probably effective (Level B), such as neuropathic pain, fibromyalgia, migraine, post-operative patient-controlled analgesia and pain, Parkinson's disease (motor and cognition), stroke (motor), epilepsy, schizophrenia, and alcohol addiction. Assessment of bias showed that most of the studies had low risk of biases, and sensitivity analysis for bias did not change these results. Effect sizes vary from 0.01 to 0.70 and were significant in about 8 conditions, with the largest effect size being in postoperative acute pain and smaller in stroke motor recovery (nonsignificant when combined with robotic therapy).

CONCLUSION

All recommendations listed here are based on current published PubMed-indexed data. Despite high levels of evidence in some conditions, it must be underscored that effect sizes and duration of effects are often limited; thus, real clinical impact needs to be further determined with different study designs.

Combined transcranial direct current stimulation and psychological interventions: State of the art and promising perspectives for clinical psychology

Recent literature shows great heterogeneity in the reported efficacy of transcranial direct current stimulation (tDCS) as a stand-alone psychiatric treatment. Aiming to increase its efficacy, tDCS has been combined with psychological interventions. Our state-of-the-art overview of such combined treatment trials indicates, however, that these usually do not elicit synergistic clinical effects. We therefore explored more basic mechanisms related to the brain state-dependency of tDCS. Importantly, based on our overview, the efficacy of combined interventions may depend on whether individual patients present with endophenotypes that are implicated in the development and maintenance of psychopathology, such as prefrontal-mediated cognitive dysfunction. We discuss how future studies may contribute to the development of personally-tailored dual active treatments by adhering to the Research Domain Criteria (RDoC) framework. RDoC-based mechanistic research may reveal alternative neural circuits that should be functionally targeted by both tDCS and psychological interventions, with promising avenues for clinical psychological science and practice.

Noninvasive brain stimulation in alcohol craving: A systematic review and meta-analysis

BACKGROUND

Alcohol dependence (AD) is characterized by a set of physical and behavioral symptoms, which may include withdrawal, tolerance and craving. Recently, noninvasive brain stimulation (NIBS) methods, namely transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), have been investigated as possible new therapeutic approaches for adjusting the pathological neuroplasticity involved in alcohol dependence. Therefore, we conducted a systematic review and meta-analysis on the therapeutic uses of tDCS and rTMS in AD patients.

METHODS

A systematic search was performed on Scopus, Web of Science, PubMed, Cochrane library and ProQuest. Search terms presented the diagnoses of interest (alcohol dependence, alcohol craving, alcohol use disorders and hazardous drinkers) and the intervention of interest (NIBS, TMS, rTMS, TBS, tDCS, tACS and transcranial). Original articles reporting the use of tDCS or rTMS to treat AD were screened and studied by two researchers independently based on PRISMA guidelines. Next, in the meta-analysis step, random-effects model was utilized to measure the pooled effect size.

RESULTS

We found 34 eligible studies including 11 tDCS trials and 23 rTMS trials. Three of these studies were case-reports, four were open label trials and the remaining 27 were controlled trials which assessed tDCS/rTMS effects on the three cognitive, behavioral and biological dimensions in AD. The pooled standardized mean differences for the effects of tDCS and rTMS on alcohol cravings were - 0.13 [-0.34, 0.08] and - 0.43 [-1.02, 0.17], respectively.

CONCLUSION

There is no evidence for a positive effect of tDCS/rTMS on various dimensions of AD. We need more randomized, double blind, sham controlled trials with enough follow-up periods to evaluate the efficacy of tDCS/rTMS for alcohol dependence treatment.

Can we boost attention and inhibition in binge drinking? Electrophysiological impact of neurocognitive stimulation

RATIONALE

Binge drinking (i.e. excessive episodic alcohol consumption) among young adults has been associated with deleterious consequences, notably at the cognitive and brain levels. These behavioural impairments and brain alterations have a direct impact on psychological and interpersonal functioning, but they might also be involved in the transition towards severe alcohol use disorders. Development of effective rehabilitation programs to reduce these negative effects as they emerge thus constitutes a priority in subclinical populations.

OBJECTIVES

The present study tested the behavioural and electrophysiological impact of neurocognitive stimulation (i.e. transcranial direct current stimulation (tDCS) applied during a cognitive task) to improve attention and inhibition abilities in young binge drinkers.

METHODS

Two groups (20 binge drinkers and 20 non-binge drinkers) performed two sessions in a counterbalanced order. Each session consisted of an inhibition task (i.e. Neutral Go/No-Go) while participants received left frontal tDCS or sham stimulation, immediately followed by an Alcohol-related Go/No-Go task, while both behavioural and electrophysiological measures were recorded.

RESULTS

No significant differences were observed between groups or sessions (tDCS versus sham stimulation) at the behavioural level. However, electrophysiological measurements during the alcohol-related inhibition task revealed a specific effect of tDCS on attentional resource mobilization (indexed by the N2 component) in binge drinkers, whereas later inhibition processes (indexed by the P3 component) remained unchanged in this population.

CONCLUSIONS

The present findings indicate that tDCS can modify the electrophysiological correlates of cognitive processes in binge drinking. While the impact of such brain modifications on actual neuropsychological functioning and alcohol consumption behaviours remains to be determined, these results underline the potential interest of developing neurocognitive stimulation approaches in this population.

Can transcranial direct current stimulation (tDCS) improve impulsivity in healthy and psychiatric adult populations? A systematic review

Impulsivity is a multidimensional phenomenon that remains hard to define. It compounds the core pathological construct of many neuropsychiatric illnesses, and despite its close relation to suicide risk, it currently has no specific treatment. Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique whose application results in cognitive function improvement, both in healthy and psychiatric populations. Following PRISMA recommendations, a systematic review of the literature concerning tDCS's effects on impulsive behaviour was performed using the PubMed database. The research was based on the combination of the keyword 'tDCS' with 'impulsivity', 'response inhibition', 'risk-taking', 'planning', 'delay discounting' or 'craving'. The initial search yielded 309 articles, 92 of which were included. Seventy-four papers demonstrated improvement in task performance related to impulsivity in both healthy and clinical adult populations. However, results were often inconsistent. The conditions associated with improvement, such as tDCS parameters and other aspects that may influence tDCS's outcomes, are discussed. The overall effects of tDCS on impulsivity are promising. Yet further research is required to develop a more comprehensive understanding of impulsivity, allowing for a more accurate assessment of its behavioural outcomes as well as a definition of tDCS therapeutic protocols for impulsive disorders.

Non-invasive Brain Stimulation for Alcohol Use Disorders: State of the Art and Future Directions

Alcohol use disorders remain one of the leading causes of mortality and morbidity across the world, yet despite this impact, there are few treatment options for patients suffering from these disorders. To this end, non-invasive brain stimulation, most commonly utilizing technologies including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS), has recently emerged as promising potential treatments for alcohol use disorders. Enthusiasm for these interventions is fueled by their non-invasive nature, generally favorable safety profile, and ability to target and modulate brain regions implicated in substance use disorders. In this paper, we describe the underlying principles behind these commonly used stimulation technologies, summarize existing experiments and randomized controlled trials, and provide an integrative summary with suggestions for future areas of research. Currently available data generally supports the use of non-invasive brain stimulation as a near-term treatment for alcohol use disorder, with important caveats regarding the use of stimulation in this patient population.

Evidence for incentive salience sensitization as a pathway to alcohol use disorder

The incentive salience sensitization (ISS) theory of addiction holds that addictive behavior stems from the ability of drugs to progressively sensitize the brain circuitry that mediates attribution of incentive salience (IS) to reward-predictive cues and its behavioral manifestations. In this article, we establish the plausibility of ISS as an etiological pathway to alcohol use disorder (AUD). We provide a comprehensive and critical review of evidence for: (1) the ability of alcohol to sensitize the brain circuitry of IS attribution and expression; and (2) attribution of IS to alcohol-predictive cues and its sensitization in humans and non-human animals. We point out gaps in the literature and how these might be addressed. We also highlight how individuals with different alcohol subjective response phenotypes may differ in susceptibility to ISS as a pathway to AUD. Finally, we discuss important implications of this neuropsychological mechanism in AUD for psychological and pharmacological interventions attempting to attenuate alcohol craving and cue reactivity.

A Randomized Trial of Combined tDCS Over Right Inferior Frontal Cortex and Cognitive Bias Modification: Null Effects on Drinking and Alcohol Approach Bias

BACKGROUND

Deriving novel treatments for alcohol use disorders (AUDs) is of critical importance, as existing treatments are only modestly effective for reducing drinking. Two promising strategies for treating AUDs include cognitive bias modification (CBM) and transcranial direct current stimulation (tDCS). While each strategy has shown positive results in reducing drinking or alcohol-related constructs (e.g., craving), initial tests of the combination of CBM and tDCS have shown mixed results. The present study investigated the degree to which combining CBM and tDCS (2.0 mA anodal current over F10) could reduce alcohol approach biases and alcohol consumption.

METHODS

Seventy-nine at-risk drinkers were randomized to 1 of 4 conditions in a 2 × 2 factorial design: verum CBM/verum tDCS, verum CBM/sham tDCS, sham CBM/verum tDCS, or sham CBM/sham tDCS. Participants completed a baseline assessment of alcohol approach bias and drinking quantity/frequency (i.e., drinks per drinking day [DDD] and percent heavy drinking days [PHDD]), 4 sessions of combined CBM and tDCS, and follow-up assessments of approach bias and alcohol consumption.

RESULTS

Results indicated that while participants did demonstrate significant alcohol approach biases at baseline, neither CBM, tDCS, nor the interaction reduced the bias at the follow-up. In addition, there was evidence of a trend toward reducing DDD from baseline to the 1-week/1-month follow-ups, but there was no significant effect of the intervention on either DDD or PHDD.

CONCLUSIONS

These results partially replicated null results presented in similar CBM/tDCS trials and suggest that this combination, at least with anodal stimulation over dorsolateral or inferior frontal sites, may have limited utility to reduce drinking.

Alcohol-Specific Computerized Interventions to Alter Cognitive Biases: A Systematic Review of Effects on Experimental Tasks, Drinking Behavior, and Neuronal Activation

Background: In patients with alcohol use disorder, novel interventions to increase abstinence have attracted growing attention. Interventions aimed at modifying cognitive biases linked to alcohol use [i.e. cognitive bias modification (CBM)] may serve as an add-on to standard therapy. This systematic review thoroughly aggregates existing data on the effects of three alcohol-specific computerized interventions, namely attentional bias modification (AtBM), approach bias modification (ApBM), and inhibition training (IT). In doing so, each CBM's effects on experimental tasks assessing the relevant biases, drinking behavior, and neurophysiology are summarized. Also, the influence of drinking behavior severity and motivation to change drinking behavior are discussed. Methods: A literature search was conducted in four databases for original research articles published between 2000 and May 2019. Studies were eligible if investigating the effects of alcohol-specific computerized interventions (AtBM, ApBM, IT) on drinking behavior, bias change, and/or neurophysiology. Forty eligible articles were classified as being either a non-clinical experimental lab study (ELS) or clinical randomized-controlled trial (RCT) and summarized. Results: While AtBM seems to influence attentional bias, its effects on drinking behavior are inconsistent. As for ApBM, the best effects on drinking behavior are obtained in clinical samples. Effects of ApBM on approach bias are mixed. Interestingly, those clinical RCTs which investigated ApBM effects on bias change as well as on drinking outcome, reported consistent effects in both measures (i.e. either effects on bias and drinking or no effects). Studies on IT are limited to non-clinical samples and show inconsistent effects on drinking behavior. Considering ITs effects on implicit semantic associations, most studies do not support the conceptualization of IT as a form of memory bias modification, while reports on IT's effects on inhibitory control are still incomplete. Conclusions about the overall influence of drinking behavior severity are hampered by the non-uniform use of sample descriptions. Conclusions: In clinical samples, ApBM has shown more consistent beneficial effects, while evidence on AtBM is more inconsistent, and data on IT still lacks important information. Conclusions about the influence of drinking behavior severity would be facilitated by a uniform use of clearly defined sample descriptions.