(PS9-C52) Applying a Drift Diffusion Model to Test the Effect of Oxytocin on Attentional Bias in Body Dysmorphic Disorder

The COVID-19 pandemic has highlighted the importance of developing novel mechanistic interventions for psychiatric disorders. Body dysmorphic disorder (BDD) is a disorder distinguished by persistent preoccupation with perceived flaws in one’s physical appearance, and is associated with impairments in selective attention. Oxytocin may improve social cognition, though its therapeutic potential in modulating social-related attentional processes in BDD has not yet been examined. The goal of this study was to examine the effects of oxytocin on modulating attention involving social stimuli. 18 participants with BDD and 15 healthy controls were recruited in the community and online. Using a randomized, placebo-controlled, within-subject crossover design, participants received a single dose of 24 international units of intranasal oxytocin (Syntocinon) or matching placebo (1 week apart). After drug administration, participants completed a spatial cueing paradigm designed to assess disengagement from social stimuli (disgust or neutral faces), based on whether cues were in the same (valid trials) or opposite (invalid trials) location as the stimuli. 

We applied a Drift Diffusion Model (DDM), a well-validated computational model, that allowed us to parse apart components of participants’ reaction time and accuracy distribution at the trial level. We isolated participants’ extradecisional time components (e.g., attentional direction to stimulus, stimulus encoding, and execution motor response; t0), drift rate (i.e. averaged cognitive speed; v), and the decisional threshold (i.e. amount of evidence needed to initiate a decision response; a). Each of these parameters was derived separately for disgust and neutral face trials in invalidly-cued trials to measure participants’ ability to disengage from negative compared to neutral stimuli. We performed separate linear mixed models on the t0, v, and a bias (difference of t0, v, a in disgust–neutral faces), with patient group and drug condition as fixed effects, visit as a repeated random effect, and visit order as a covariate. We found a significant effect of group across all parameterswith BDD patients displaying higher t0 (F = 5.94, p = 0.02), lower v (F = 4.35, p = 0.045), and lower a (F = 6.50, p = 0.02), compared to controls on disgust–neutral trials. This indicates that on disgust versus neutral trials, BDD patients took longer to disengage from the invalidly-cued stimuli (higher t0), showed lower cognitive speed during the actual decision-process (lower v), and decreased conservativeness within their decision making style (lower a). However, no significant effect (all p > 0.08) of the drug was observed, nor any group by drug interaction effects, indicating that oxytocin (relative to placebo) did not modulate negative social-attentional biases in BDD patients. Our results point to a distinct attentional bias in BDD characterized by difficulty disengaging from disgust faces that is separate from biases in decision making. Further research is needed to replicate these results with a larger sample.