Preliminary Examination of Sympathetic Magic as a Psychological Endophenotype for Obsessive-Compulsive Disorder.

Although sympathetic magic (SM) beliefs (i.e., irrational understanding of contagion transmission) are observed in obsessive-compulsive disorder (OCD), it is unclear if such beliefs are psychological endophenotypes. Furthermore, predictors of SM beliefs in OCD remain unknown. Accordingly, the present study examined whether SM beliefs function as an endophenotype for OCD and whether perceived vulnerability to disease (PVD) contributes to SM beliefs. A sample of 30 individuals with OCD, 26 first-degree relatives, and 25 age-matched healthy controls completed self-report questionnaires and a SM task where we touched a clean pencil to a "contaminated" toilet, and rated the degree to which the pencil was contaminated. A second pencil was touched to the first pencil and was then rated. This process was continued for 12 pencils (12 degrees of removal from contagion). Results revealed no significant differences in the extent to which the three groups perceived a "chain of contagion" (i.e., contamination slopes) for the successive degrees of removal from the original contagion. However, the OCD group reported significantly less contamination reduction on the task, a group difference that was mediated by PVD. These findings suggest that although SM beliefs may not be an OCD endophenotype, such beliefs may derive from a PVD.