Abstract
Reductions in judgmental biases concerning the cost and probability of negative social events are presumed to be mechanisms of treatment for SAD. Methodological limitations of extant studies, however, leave open the possibility that, instead of causing symptom relief, reductions in judgmental biases are correlates or consequences of it. The present study evaluated changes in judgmental biases as mechanisms explaining the efficacy of CBT for SAD. Participants were 86 individuals who met DSM-IV-TR criteria for a primary diagnosis of SAD, participated in one of two treatment outcome studies of CBT for SAD, and completed measures of judgmental (i.e., cost and probability) biases and social anxiety at pre-, mid-, and posttreatment. Treated participants had significantly greater reductions in judgmental biases than not-treated participants; pre-to-post changes in cost and probability biases statistically mediated treatment outcome; and probability bias at midtreatment was a significant predictor of treatment outcome, even when modeled with a plausible rival mediator, working alliance. Contrary to hypotheses, cost bias at midtreatment was not a significant predictor of treatment outcome. Results suggest that reduction in probability bias is a mechanism by which CBT for SAD exerts its effects.