OCD has been conceptualized as a disorder arising from dysfunctional beliefs, such as overestimating threads or pathological doubts. Yet, how these beliefs lead to compulsions and obsessions remains unclear. Here, we develop a computational model to examine the specific beliefs that trigger and sustain compulsive behavior in a simple handwashing scenario. Our results demonstrate that a single belief disturbance – a lack of trust in one’s avoidance action– can trigger and maintain compulsions and is directly linked to compulsion severity. This distrust can further explain a number of seemingly unrelated phenomena in OCD including the role of not-just-right feelings, intolerance to uncertainty, overestimation of threat or perfectionisms, and deficits in reversal and state learning. In conclusion, our findings shed new light on the underlying beliefs that drive compulsive behavior in OCD, providing a step forward in building a more comprehensive theory of this complex condition.
