Obsessive-compulsive disorder (OCD) is relatively common (Ruscio, Stein, Chiu, & Kessler, 2010) and leads to significant functional impairment (World Health Organization, 2001). Research suggests that exposure and response prevention (EX/RP) is efficacious for reducing OCD symptoms (NICE, 2006); however, standard outpatient EX/RP does not effectively alleviate symptom severity among a substantial proportion of OCD patients (Abramowitz, 2006). Intensive EX/RP programs have been developed to address the needs of treatment-refractory OCD patients (Veale et al., 2016). While evidence from effectiveness studies suggests that intensive EX/RP programs lead to significant reductions in OCD symptom severity, a portion of patients do not demonstrate improvement in response to intensive treatment (e.g., Björgvinsson, Hart, et al., 2013; Boschen, Drummond, & Pillay, 2008). These findings underscore the need to identify reliable predictors of OCD patient response to intensive EX/RP to help target clinical and research efforts toward improving treatment outcomes for those least likely to respond to current treatment modalities. Therefore, the proposed study evaluated distinct trajectories of OCD symptom change across six-weeks of intensive treatment and examined factors that predict membership in those trajectory groups. Results suggested that three latent subgroups of OCD patients emerged with one demonstrating symptom relapse during intensive treatment. Further, OCD symptom severity was the only baseline factor that predicted latent-class membership. Implications and future directions of research are discussed.

Previous research has revealed heterogeneity in outcome trajectories among individuals seeking psychotherapy. However, questions remain as to the number, nature, and predictors of these trajectories. Therefore, the present study had three aims: 1) to identify heterogeneous latent groups among treatment trajectories of 212 clients with major depressive disorder (MDD) seeking psychotherapy at a community mental health training clinic; 2) to identify significant associations between clinical and demographic variables and group membership; and 3) to identify correlations between trajectory shape and positive treatment outcome. Prior to treatment, participants provided demographic information and completed symptom severity ratings. Once in treatment, participants completed a self-report of distress via the Outcome Questionnaire (OQ-45) at every session. Growth mixture modeling was utilized to identify distinct patient subgroups based on outcome trajectories among the sample. Three distinct latent classes of treatment trajectory were identified, providing evidence of heterogeneity in treatment trajectories among individuals with MDD. Baseline distress, pre-treatment work problems, and sleep difficulties were found to be predictive of an individual's membership in a specific trajectory group. Finally, specific shapes of change, namely early response and sudden gains, were associated with positive treatment outcome. Findings from this study can be used to identify patients at risk for treatment failure, allowing clinicians to intervene earlier to enhance mid-treatment feedback and prognosis.