Sudden gains in exposure therapy for obsessive-compulsive disorder.

Prior research in the treatment of depression and anxiety has demonstrated that a sudden reduction in symptoms between two consecutive sessions (sudden gain) is related to lower post-treatment symptom severity (e.g. Hofmann, Schulz, Meuret, Moscovitch, & Suvak, 2006; Tang & DeRubeis, 1999). However, only one study has examined sudden gains in the treatment of obsessive compulsive disorder (OCD). In that study, one-third of the patients with OCD experienced a sudden gain (Aderka et al., 2012). Further, patients who had a sudden gain had lower clinician-rated OCD symptom severity post-treatment (Aderka et al., 2012). In replication, the current study examined the frequency, characteristics, and clinical impact of sudden gains in 27 OCD patients during exposure and response prevention (ERP) therapy. Fifty two percent of patients experienced a sudden gain. The mean magnitude of a sudden gain represented, on average, 61.4% of total symptom reduction. Following treatment, individuals who had experienced a sudden gain were rated as less severe on the clinical global impression scale, but they did not experience a greater reduction in OCD symptoms (pre-to post-treatment) than those without a sudden gain. None of the pre-treatment characteristics tested were found to significantly predict whether a patient would have a sudden gain. Additional research examining predictors of, and patterns of, change in OCD symptoms is warranted.