A systematic review of predictors and moderators of response to psychological therapies in OCD: do we have enough empirical evidence to target treatment?

Obsessive-compulsive disorder (OCD) is a disabling mental health condition. Despite effective psychological treatments for OCD, a significant percentage of patients fail to experience lasting benefit. Factors underlying variable treatment response are poorly understood. Moderators of outcome can help understand "for whom" and "under what circumstances" an intervention works best and thus improve service effectiveness. This paper synthesizes the evidence on predictors and moderators and assesses the quality of reporting of related analyses in psychological therapies for adults with OCD. Trials were identified through electronic searches (CENTRAL, MEDLINE, PsycINFO, EMBASE), key author, and reference list searches of relevant systematic reviews. Fifty five percent (38/69) of relevant trials reported baseline factors associated with outcome; these encompassed clinical, demographic, interpersonal, OCD symptom-specific, psychological/psychosocial, and treatment-specific variables. Predictors were commonly assessed via a validated pre-randomization measure, though few trials adopted best practice by stating a priori hypotheses or conducting a test of interaction. Potential associations emerged between worse OCD treatment outcome and the following factors: hoarding pathology, increased anxiety and OCD symptom severity, certain OCD symptom subtypes, unemployment, and being single/not married. However, the applied utility of these analyses is currently limited by methodological weaknesses.