Ancillary Effects of High-Definition tDCS on Psychophysiology and Cognition in Adults Under Pharmacological Treatment for Anxiety Disorders
Authors:   , Orsini Taylor J. , Chysikou Evangelia 
Published: September 2023

Anxiety disorders are the most prevalent mental health disorder globally; yet the research dedicated to their study is disproportionately small. Anatomically, anxiety disorders are characterized by dysfunction in the limbic system and the prefrontal cortex (PFC). In the PFC specifically, previous research has indicated an imbalance between the left and right dorsolateral prefrontal cortex (dlPFC), wherein the left dlPFC is hypoactive, whereas the right dlPFC is hyperactive. Several cognitive deficits are associated with anxiety disorders-including, but not limited to, poor concentration, defective learning and working memory, longer decision-making latencies, and more. Although psychopharmacological treatments, such as selective serotonin reuptake inhibitors (SSRIs) and benzodiazepines, have shown to have positive effects for symptom reduction in anxiety disorders, little investigation has been dedicated to their impact on the cognitive deficits associated with the disease, or cognition in general. An alternative therapeutic intervention for psychiatric disorders, transcranial direct current stimulation (tDCS), has shown positive results for cognition in healthy and clinical populations. The goal of this study was to investigate the ancillary effects of high-definition 4 x 1 transcranial direct current stimulation (tDCS) on psychophysiology and cognition in patients with anxiety disorders who are treated with psychopharmacological agents, specifically SSRIs and benzodiazepines. The participant pool constitutes students currently enrolled at Drexel University who are clinically diagnosed with an anxiety disorder and who are either unmedicated, prescribed and taking an SSRI, or prescribed and taking a benzodiazepine. High-definition tDCS was applied in a within-subjects design under three different conditions: sham, active anodal tDCS over the left dlPFC, and active cathodal tDCS over the right dlPFC. Each participant received each type of stimulation, one per session for a total of three sessions. Throughout the study and during stimulation, participants completed various questionnaires and cognitive tasks. Based on prior literature, I hypothesized that participants treated with SSRIs would perform significantly better on the cognitive battery independent of the active stimulation conditions (anodal or cathodal). I further hypothesized that participants treated with benzodiazepines would perform significantly worse on the cognitive tasks compared to the other treatment groups, independent of any stimulation condition. I also hypothesized that active tDCS stimulation, either anodal stimulation over the left dlPFC or cathodal stimulation over the right dlPFC, would elicit significant reductions in anxiety symptom severity and better performance on cognitive tasks than sham stimulation in the SSRI treatment subgroup. Lastly, I hypothesized that active and sham stimulation conditions would elicit positive results for anxiety symptoms but null results for cognition for the benzodiazepine treatment subgroup, due to the sedative effects of benzodiazepine treatment. Independent two sample t-tests, and one-way and two-way ANOVAs, were run as a part of the preliminary analysis of the data collected. No statistical significance was observed in this preliminary sample, but some tests in the future could potentially lead to significant results with the inclusion of more participants, as discussed more in the discussion section.