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In this article, we develop a computational model of obsessive compulsive disorder (OCD). We propose that OCD is characterized by a difficulty in relying on past events to predict the consequences of patients' own actions and the unfolding of possible events. Clinically, this corresponds both to patients' difficulty in trusting their own actions (and therefore repeating them), and to their common preoccupation with unlikely chains of events. Critically, we develop this idea on the basis of the well-developed framework of the Bayesian brain, where this impairment is formalized as excessive uncertainty regarding state transitions. We illustrate the validity of this idea using quantitative simulations and use these to form specific empirical predictions. These predictions are evaluated in relation to existing evidence, and are used to delineate directions for future research. We show how seemingly unrelated findings and phenomena in OCD can be explained by the model including: a persistent experience that actions were not adequately performed and a tendency to repeat actions; excessive information gathering (i.e. checking); indecisiveness and pathological doubt; overreliance on habits at the expense of goal-directed behavior; and over-responsiveness to sensory stimuli, thoughts, and feedback. We discuss the relationship and interaction between our model and other prominent models of OCD, including models focusing on harm-avoidance, not-just-right experiences, or impairments in goal-directed behavior. Finally, we outline potential clinical implications and suggest lines for future research.

Several recent models of obsessive compulsive disorder (OCD) consider it to be a neurocognitive disorder involving inflexibility and disinhibition. Indeed, previous reviews of neuropsychological functioning in OCD suggested impaired performance in flexibility tasks. The current meta-analysis examines whether the reported differences in flexibility can be explained by general underperformance unrelated to flexibility. In addition, the role of feedback processing in inflexibility is investigated. To this end, we integrated evidence from 75 studies that compared patients with OCD with nonpsychiatric controls on at least one flexibility measure, while applying a novel approach in which task scores measuring flexibility were compared with control scores from the same tasks measuring other confounding processes. The results revealed no evidence for inflexibility in OCD, with patients’ performance most parsimoniously explained by nonspecific factors. These results challenge models stressing inflexibility as an endophenotype of OCD. Methodological implications for reviewing cognitive deficits in psychopathology are discussed.

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Scrupulosity, or obsessive-compulsive symptoms related to religiosity or religion, is a common presentation of obsessive compulsive disorder (OCD), and it is important to elucidate its phenomenology and measurement. Today, the most widespread questionnaire for the assessment of scrupulosity is the Penn Inventory of Scrupulosity (PIOS). The current study examines the psychometric properties of the PIOS in outpatient, treatment-seeking patients. Results of a confirmatory factor analysis suggested an unsatisfactory fit for previously suggested factor structures. A follow-up exploratory factor analysis suggested that a bifactor model was the most suitable solution. In addition, the scores of the PIOS and its revised subscales were found to have moderate-good concurrent validity; however, its scores discriminated poorly between patients with scrupulous obsessions and patients with OCD and other repugnant obsessions. Group differences and receiver operating characteristics (ROC) analyses both indicated that the PIOS is more suitable in discriminating scrupulous obsessions in Christian patients but not in other religious groups (i.e., Jews, nonreligious patients). Additional analyses revealed that the co-occurrence of scrupulous and other repugnant obsessions is also moderated by religious affiliation. These results raise questions in terms of grouping scrupulosity with other repugnant obsessions and suggest for the need of culturally sensitive instruments of scrupulosity. (PsycINFO Database Record