Augmenting Virtual Reality Exposure Therapy for Social and Intergroup Anxiety With Transcranial Direct Current Stimulation

Abstract

Objectives: Exposure therapy is a cornerstone of social anxiety treatment, yet not all patients respond. Symptoms in certain social situations, including intergroup (ie, out-group) contexts, may be particularly resistant to treatment. Exposure therapy outcomes may be improved by stimulating neural areas associated with safety learning, such as the medial prefrontal cortex (mPFC). The mPFC also plays an important role in identifying others as similar to oneself. We hypothesized that targeting the mPFC during exposure therapy would reduce intergroup anxiety and social anxiety.

Methods: Participants (N = 31) with the public speaking subtype of social anxiety received active (anodal) or sham transcranial direct current stimulation (tDCS) targeting the mPFC during exposure therapy. Exposure therapy consisted of giving speeches to audiences in virtual reality. To target intergroup anxiety, half of the public speaking exposure trials were conducted with out-group audiences, defined in this study as audiences of a different ethnicity.

Results: Contrary to hypotheses, tDCS did not facilitate symptom reduction. Some evidence even suggested that tDCS temporarily increased in-group favoritism, although these effects dissipated at 1-month follow-up. In addition, collapsing across all participants, we found reductions across time for public speaking anxiety and intergroup anxiety.

Conclusions: The data provide evidence that standard exposure therapy techniques for social anxiety can be adapted to target intergroup anxiety. Transcranial direct current stimulation targeting the mPFC may boost safety signaling, but only in contexts previously conditioned to signal safety, such as an in-group context.

Trial registration: ClinicalTrials.gov NCT03743571.

Figure 1

Procedural Overview Note. Experimental design and procedures. Part A depicts the flow of procedures from the beginning to end of the study. Part B depicts the VR public speaking environment and audiences which were used for speech tasks during behavioral assessments (BATs) and exposure therapy trials. Part C depicts the electrode placements for the study’s tDCS montage.

Figure 1

Procedural Overview Note. Experimental design and procedures. Part A depicts the flow of procedures from the beginning to end of the study. Part B depicts the VR public speaking environment and audiences which were used for speech tasks during behavioral assessments (BATs) and exposure therapy trials. Part C depicts the electrode placements for the study’s tDCS montage.

Figure 2

Treatment Process tDCS × Audience Interactions Note. For participants receiving active stimulation targeting the mPFC, in-group audiences were rated with lower expected threat ($M=28.79$ ($SE=6.47$) vs $M=32.44$ ($SE=6.66$); $p=.042$) and anxiety ($M=49.94$ ($SE=5.21$) vs $M=53.85$ ($SE=4.69$); $p=.011$) than out-group audiences. For participants receiving sham stimulation, there were no significant differences between in-group and out-group audiences for expected anxiety ($M=56.67$ ($SE=5.38$) vs $M=54.87$ ($SE=4.84$); $p=.235$) and expected threat ($M=39.47$ ($SE=6.68$) vs $M=35.84$ ($SE=6.88$); $p=.050$). The means displayed above are marginal means representing an average of all trials conducted during VR exposure therapy.

Figure 2

Treatment Process tDCS × Audience Interactions Note. For participants receiving active stimulation targeting the mPFC, in-group audiences were rated with lower expected threat ($M=28.79$ ($SE=6.47$) vs $M=32.44$ ($SE=6.66$); $p=.042$) and anxiety ($M=49.94$ ($SE=5.21$) vs $M=53.85$ ($SE=4.69$); $p=.011$) than out-group audiences. For participants receiving sham stimulation, there were no significant differences between in-group and out-group audiences for expected anxiety ($M=56.67$ ($SE=5.38$) vs $M=54.87$ ($SE=4.84$); $p=.235$) and expected threat ($M=39.47$ ($SE=6.68$) vs $M=35.84$ ($SE=6.88$); $p=.050$). The means displayed above are marginal means representing an average of all trials conducted during VR exposure therapy.

Figure 3

Treatment Outcome Audience × Time Interaction Note. Performance for tDCS conditions are shown separately for descriptive purposes; however, the significant interaction was an audience × time interaction and did not include tDCS condition. Audience context (in-group vs out-group) moderated the reduction from baseline to one-month follow up in ratings of peak anxiety reported during BATs, behavioral tests of public speaking fear. Simple effects analyses of means collapsed across tDCS condition demonstrate an in-group bias at baseline (in-group $M=61.08$ ($SE=5.72$) vs out-group $M=69.23$ ($SE=4.87$); $p=.030$) that is no longer present at one-month follow-up (in-group $M=31.16$ ($SE=4.67$) vs out-group $M=31.28$ ($SE=4.45$); $p=.959$). Thus, conducting exposure therapy in both in-group and out-group contexts may reduce in-group bias, although tDCS was not shown to potentiate this effect.