Hunt, Christopher2021-10-132021-10-132021-09https://hdl.handle.net/11299/224967University of Minnesota Ph.D. dissertation.September 2021. Major: Psychology. Advisor: Shmuel Lissek. 1 computer file (PDF); ix, 275 pages.Although the obsessions implicated in obsessive compulsive disorder (OCD) could theoretically involve any distressing topic, they typically gravitate toward a handful of specific themes (e.g., contamination, religion, sex, etc.). The universality of these themes across OCD patients from different time periods, cultures, and age-groups suggests they are manifestations of a common, underlying process, but little effort has been made to elucidate the identity of this process. One intriguing feature shared across most common obsessions is a heightened concern with consequences that are objectively terrible but highly unlikely (e.g., catching HIV from a door knob, being sent to hell for a fleeting immoral thought). The ubiquity of this particular consequence suggests that OCD may be characterized by an underlying sensitivity to improbable catastrophes (SIC), but this possibility has yet to be explored. The present dissertation sought to address this gap by examining whether OCD symptoms predicted higher anxious reactivity toward unlikely, highly aversive threats across three experimental studies. In the first study, college students with higher OCD symptoms exhibited greater avoidance of improbable, highly aversive threats, as well as greater expectancy and physiological reactivity for improbable threats in general. An extension of this investigation with different types of experimental threats (study two) showed that OCD symptoms predicted heightened expectancy of improbable threats involving both harmful and disgust-related consequences, while relations between OCD symptoms and avoidance of improbable, highly aversive consequences were specific to harmful threats. Finally, study three showed that differences in expectancy, anxiety, and avoidance for improbable threats prospectively predicted changes in OCD symptoms over the first year of college, with indices of anxious reactivity to improbable threat (anxiety, startle, avoidance) emerging as especially predictive among participants who rated the threat as highly aversive. Together, these studies implicate SIC as a novel pathogenic marker of OCD, and suggest its role in the illness may derive from a more general tendency to overestimate the likelihood of improbable outcomes bearing high subjective costs.enAvoidanceDecision-makingFear ConditioningObsessive-Compulsive DisorderThreat ProbabilityThreat SeverityThesis or Dissertation