Internet-based cognitive bias modification for obsessive compulsive disorder: study protocol for a randomized controlled trial

Background: Cognitive bias modification (CBM) interventions have demonstrated efficacy in augmenting core biases implicated in psychopathology. The current randomized controlled trial (RCT) will evaluate the efficacy of an internet-delivered positive imagery cognitive bias modification intervention for obsessive compulsive disorder (OCD) when compared to a control condition. Methods/Design: Patients meeting diagnostic criteria for a current or lifetime diagnosis of OCD will be recruited via the research arm of a not-for-profit clinical and research unit in Australia. The minimum sample size for each group (alpha set at 0.05, power at .80) was identified as 29, but increased to 35 to allow for 20% attrition. We will measure the impact of CBM on interpretations bias using the OC Bias Measure (The Ambiguous Scenarios Test for OCD ;AST-OCD) and OC-beliefs (The Obsessive Beliefs Questionnaire-TRIP; OBQ-TRIP). Secondary outcome measures include the Dimensional Obsessive-Compulsive Scale (DOCS), the Patient Health Questionnaire (PHQ-9), The Kessler Psychological Distress Scale (K10), and the Word Sentence Association Test for OCD (WSAO). Change in diagnostic status will be indexed using the OCD Mini International Neuropsychiatric Interview (M.I.N.I) Module at baseline and follow up. Intent to treat (ITT) marginal and mixed effect models using restricted maximum likelihood (REML) estimation will be used to evaluate the primary hypotheses. Stability of bias change will be assessed at 1-month follow-up. Discussion: A limitation of the online nature of the study is the inability to include a behavioral outcome measure.