Mental Contamination in Obsessive-Compulsive Disorder: Associations With Contamination Symptoms and Treatment Response

The most common symptom of obsessive-compulsive disorder (OCD) is contamination fear. Feelings of contamination can be provoked through contact with a physical contaminant, referred to as contact contamination (CC), as well as in the absence of one, referred to as mental contamination (MC). Prior research indicates that CC and MC are distinct, and MC may interfere with treatment for CC. However, no study to date has examined how MC may be associated with responses to physical contaminants and treatment response for CC. This study examined the relationships between CC and MC in a sample of individuals with elevated contamination symptoms (N = 88), half of whom met diagnostic criteria for OCD. Participants engaged in three sessions of exposure and response prevention (ERP) for CC and completed self-report measures and behavioral tasks assessing CC and MC at pretreatment, posttreatment, and follow-up. As hypothesized, at pretreatment, MC was positively associated with reactivity to physical contaminants, even after participants washed their hands. ERP for CC was associated with unique changes in CC and MC across self-report and behavioral measures, and greater pretreatment MC predicted greater posttreatment CC, though this effect was evident in only one of two CC measures. Additionally, specificity analyses indicated changes in MC were independent of changes in disgust propensity, a related construct. Pretreatment disgust propensity also predicted treatment outcome, though the addition of pretreatment disgust propensity as a covariate reduced the relationship between pretreatment MC and posttreatment CC to nonsignificance. Results suggest MC plays an important role in the manifestation and treatment of CC symptoms and may represent a manifestation of disgust proneness. Theoretical and clinical implications are discussed.