Non-invasive Brain Stimulation of the Prefrontal Cortex in Substance Use Disorders

Overview

Every year, alcohol causes 3 million deaths worldwide. Even though a lot of treatments already exist, many of them are characterized by a high percentage of drop-out or relapse. Transcranial direct current stimulation (tDCS), a NIBS, is receiving increased attention as a possible new addiction treatment. However, little consensus exists in the concrete parameters (e.g. montage, current, intensity). Moreover, a lot of tDCS research focuses on subjective outcomes, like the report of craving, which are more prone to different biases and fluctuations. In this study, we aim to investigate the effect of HD-tDCS, a more focal stimulation variant, on AUDs. Using this intervention, stimulation can be restricted to one hemisphere, controlling for possible inhibition effects of the cathode. A between-subject design will be carried out, including patients with an AUD. Participants will receive 5 sessions of either real or sham right anodal HD-tDCS over the dorsolateral prefrontal cortex (dlPFC). Craving will be accounted for at baseline and after every stimulation session. Moreover, we will measure the activity of the brain in rest and during two inhibition tasks (Go/NoGo and cue reactivity task). This objective measure will be carried out both before (baseline) and at two time points after the stimulation, to measure effects on both the short and longer term. One month after the intervention, abstinence will be checked through a follow-up phone call. Through this study, we aim to describe positive effects of right dlPFC stimulation on craving, abstinence, and EEG measures.

Population This study will focus on patients with AUD, as these are the easiest to recruit. Participants in this study will be enrolled in a residential SUD treatment or a day hospital SUD treatment. As such, medical supervision can be guaranteed. In addition, sobriety is assessed objectively and routinely as part of TAU, enabling exclusion of patients under influence of alcohol. Cognitive impairment will be assessed using the MoCA and participants with a score below 10 (severe cognitive impairment) will be excluded. Design This study will use a between-subjects design. The experiment will be conducted double-blind to minimalize placebo effects and researcher bias. Group allocation will be conducted semi-randomly, with matching of participants' sex. The otherwise identical placebo protocol features sham stimulation (after a short ramp up, current drops again). The short ramp up is used to induce the same sensations as in the stimulation group (possible itching and tingling). Measures Self-report Self-report measures will be collected prior to the intervention to discern endophenotypes predicting treatment response. The Behavioral Inhibition/Behavioral Activation System (BIS/BAS), Effortful Control Scales, Barrat Impulsiveness Scale and the Alcohol Use Disorders Identification Test (AUDIT) are collected. The Beck Depression Inventory (BDI) will be collected both before and after intervention. Cognitive screening The Montreal Cognitive Assessment (MoCA) will be used to exclude patients with severe cognitive impairment. Participants with a score of 10 or lower on the MoCA will be excluded from the study. Medication regime The medication regime of the participants will be registered, since medication may influence tDCS effects. Resting state EEG A resting state EEG is collected before the intervention as well as immediately after the first stimulation session and after the last stimulation session. These timepoints are used to collect data concerning the effect of tDCS on both short term and longer term. ERPs and behavioral measures Apart from resting state, event related potentials (ERP's) will be collected at the same time points, during different behavioral tasks: a cue reactivity task reflecting activation of the reward system and a Go-NoGo task reflecting executive functions, more concrete response inhibition. * Cue-reactivity task: In this task, participants will be requested to indicate the occurrence of any infrequent stimulus by pressing the response button as fast as possible. Participants will be shown successions of pictures of a person drinking water (frequent), alcohol (infrequent) or soft drinks (equally infrequent). All stimuli will be presented in a random order. Three different alcohol-related pictures will be used, selected during the screening for alcohol preference. * Go/NoGo task: In this task, participants have to press a button as fast as possible, whenever the Go stimulus (the letter M) is displayed. When another, infrequent stimulus is displayed (NoGo, the letter W), they have to refrain from pressing the button. The letters are superimposed on an alcohol-related picture or a non-alcohol related picture. In both tasks, trials followed by incorrect responses will be eliminated from the data set. Reaction times and percentage of errors will be registered as behavioral measures. Safety and blinding After every session of HD-tDCS adverse effects will be assessed. Moreover, participants will systematically be asked whether they believe to have received real or placebo stimulation in the past session. Subjective craving A subjective craving measure will be carried out before the intervention and after every stimulation session. Follow-up 1 month after the last stimulation session, verbally self-reported abstinence status will be registered. To do so, the Quick Drinking Screen (QDS) will be used. Intervention 5 sessions of 2mA HD-tDCS (active or sham) will be used as intervention during 20 minutes.