A clinical trial evaluating the effects of combined transcranial direct current stimulation and alcohol approach bias retraining

Introduction: In two large clinical studies alcohol approach bias retraining, in which patients learn to avoid alcohol pictures (by pushing them with a joystick), has been found to be effective in reducing approach bias and increasing treatment outcome for alcohol patients. This form of training is called Cognitive Bias Modification (CBM). It is hypothesized that stimulation of the prefrontal cortex with transcranial direct current stimulation (tDCS) may improve this training. TDCS is a technique with which a small electrical current can be sent through the cortex, this is believed to influence neuronal polarization and increase plasticity; and thus can possibly enhance learning effects. Also, anodal tDCS over the dorsolateral prefrontal cortex (DLPFC) has been found to reduce craving for alcohol. Objectives: This study investigated whether transcranial Direct Current Stimulation (tDCS) could enhance effects of CBM on craving, approach bias, and relapse. Materials & method: One hundred alcohol-dependent inpatients (91 used for analysis) were randomized into 3 experimental groups in a double-blind parallel design. The experimental group received 4 sessions of CBM while receiving 2 mA of anodal tDCS over the DLPFC. There were two control groups: One received sham stimulation during training and one received active stimulation at a different moment in time. Before and after the treatment sessions there was a pre and post assessment; outcome measurements were alcohol approach bias (Approach Avoidance Task (AAT) & Implicit Association Test (IAT)), craving (Penn Alcohol Craving Scale (PACS) and relapse. Results: Craving and approach bias scores decreased over time, but there were no significant interactions with experimental condition. There was an indication of a beneficial effect of tDCS on approach bias only early in the training, from the first to second session. There was no effect on abstinence duration after three months. However, relapse rates after one year were lower in the conditions that received active stimulation. Conclusion: The current study presents a novel combination of CBM and tDCS for treatment of alcohol dependence. No strong evidence for a specific enhancement effect of tDCS on CBM was found. However, tDCS irrespective of timing relative to CBM showed promising effects on treatment outcome