Efficacy of tDCS to enhance virtual reality exposure therapy response in acrophobia: A randomized controlled trial

[BACKGROUND]: Virtual reality exposure therapy (VRET) has been recognized as an effective treatment for specific phobias and has the potential to overcome the limitations of traditional exposure therapy. The pursuit of non-invasive brain stimulation provides a practical means of augmenting VRET. Transcranial direct current stimulation (tDCS), a non-invasive neuromodulation technique, stimulates the medial prefrontal cortex (mPFC), with the potential to enhance the effects of exposure therapy. Therefore, we conducted a randomized controlled trial to examine whether tDCS enhanced the effects of VRET in acrophobia. [METHOD]: This study recruited 64 college students with significant fear of height (based on the Acrophobia Questionnaire, AQ). Finally, 61 participants were randomly allocated to the tDCS active-stimulated group (n = 30) or the sham-stimulated group (n = 31). After stimulation, VRET was conducted, and clinical indices were recorded. The AQ was used as the first primary outcome, and Subjective Units of Distress (SUDS) and the Heights Interpretation Questionnaire (HIQ) were used as secondary outcomes. [RESULT]: There was a significant reduction in psychometric and behavioral anxiety measurements from pre to post treatment as indicated by main effects for the factor time (AQ-Anxiety: F (2.60) = 139.55, p < 0.001, η2 = 0.83; AQ-Avoidance: F (2.60) = 53.73, p < 0.001, η2 = 0.69; HIQ: F (2.60) = 128.12, p < 0.001, η2 = 0.81; STAI-Y-S: F (2.60) = 15.44, p < 0.001, η2 = 0.34; BAI: F (2.60) = 73.81, p < 0.001, η2 = 0.71). Compared with the sham-stimulated group, the reduction of AQ-Anxiety and SUDS in the first exposure trial (F (2,60) = 8.56, p = 0.001, η2 = 0.23; t = 2.34, p = 0.024, d = 0.61) was significantly faster in the active group. At follow-up, there was also a further reduction in AQ anxiety and avoidance (Anxiety: M = 56.51 ± 27.19; main effect time F (1,60) = 25.16, p < 0.001, η2 = 0.35; Avoidance: M = 12.57 ± 7.97; main effect time F (1,60) = 31.40, p < 0.001, η2 = 0.45) without interaction time*group (Anxiety: F (1.60) = 0.12, p = 0.740, η2 = 0.00; Avoidance: F (1.60) = 0.64, p = 0.430, η2 = 0.02). [CONCLUSION]: Results could be explained tDCS could accelerate the effects of VRET on acrophobia by stimulating mPFC, indicating that tDCS may be used as an enhancement technique for exposure therapy for specific phobias.