tDCS-augmented exposure therapy for pathological fears

Abstract

Exposure therapy is remarkably effective for treating anxiety and stress-related problems. Still, there is a need to enhance the efficacy, efficiency, and palatability of exposure. Recent efforts have sought to optimize extinction learning, through procedural variations, or by targeting underlying cellular mechanisms. Guided by evidence that brain stimulation can functionally target brain networks implicated in fear expression and extinction learning, the present study is a 2-arm, double-blind, placebo-controlled trial testing whether transcranial direct current stimulation (tDCS) can augment exposure therapy for several forms of pathological fear. Participants (N = 49) with at least moderate distress in response to snakes, spiders, or contamination-related threats were randomized to receive either active tDCS (1.7 mA, 20 min.; n = 27), or sham tDCS (1.7mA, 30 sec.; n = 22), followed by 30 min. of in-vivo exposure. Electrodes targeted excitation of the left medial prefrontal cortex (lmPFC) and inhibition of the right dorsolateral prefrontal cortex (rdlPFC) for those assigned to active tDCS, whereas polarity was counterbalanced across controls. The active tDCS group exhibited greater gains compared to sham tDCS in primary and secondary outcomes, including reductions in distress and threat appraisals through the 1-month follow-up, although these findings did not uniformly generalize to an untrained context. The active tDCS group also exhibited more rapid cognitive change during exposure, and enhanced approach in early exposure trials. Active tDCS also especially enhanced outcomes for those with greater phobic severity, a poorer response to exposure, elevated anxiety sensitivity, and an avoidant coping style. Exploratory analyses revealed tDCS-augmentation effects were partially accounted for by increased attentional and behavioral engagement with threat. Future research should apply tDCS to more severe conditions, and yoke stimulation to individual differences to maximize and promote the retention of clinical gains