Summary: | Contamination fear features prominently in obsessive compulsive disorder (OCD), but little is known about its various subtypes. In addition to the better-recognised contact contamination, feelings of dirtiness can occur in the absence of physical contact with a contaminant; this is referred to as mental contamination. Morphing fear, or a fear of being tainted by negative characteristics of others, is conceptualised as a type of mental contamination. This thesis investigates different contamination fears in OCD with the goal of understanding their phenomenology and aetiology, aiding in assessment, and advancing treatment Part I of this thesis focuses on the aetiology and reduction of contamination fears. Retrospective interviews with 30 clinical OCD participants with contamination concerns revealed the majority believed their onset was due to learning events. Negative learning experiences were found to be a viable determinant in contact contamination fear acquisition in an experiment using 76 non-fearful non-clinical participants. Another experiment gave some indication that contact contamination fears can be reduced though positive or neutral learning experiences in a non-clinical analogue sample with significant contamination fears (n = 55). Of interest in Part 11 of this thesis is the assessment and treatment of morphing fear. A questionnaire was developed to help assess for the presence and degree of morphing fear, with the aim to be useful in further research and clinical practice. Approximately 1263 participants were used in the development of the measure; the questionnaire was tested on a control and self-reported OeD group and was found to have good psychometriC properties. A novel cognitively-based CBT intervention for morphing fear was successful in reducing symptom severity of an OCD sufferer in a Single-case quasi-experimental design.
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