The probability of change versus dropout in veterans receiving Cognitive Processing Therapy for posttraumatic stress disorder.

OBJECTIVE: We sought to elucidate the timing of symptom change and treatment dropout in a leading evidence-based psychotherapy for posttraumatic stress disorder, Cognitive Processing Therapy (CPT). Despite its efficacy across numerous populations, treatment nonresponse and premature dropout are common in CPT and other trauma-focused interventions, particularly among military veterans. Advancements are therefore needed to reduce dropout and increase retention. METHOD: Survival analysis was used to identify the temporal probability of symptom amelioration at each session of CPT (with written trauma account; CPT-A) and compare this with the cumulative, session-by-session probability of dropout. Data were obtained from 194 veterans seeking outpatient treatment at a Veterans Affairs specialty clinic. RESULTS: Overall, 49-61% of veterans reported meaningful symptom reduction in the course of CPT-A and 40% dropped out prematurely. The cumulative probability of dropout exceeded the probability of symptom change beginning after session six of therapy. Secondary analyses indicated that this six session rule generalized well across subgroups. CONCLUSIONS: When symptom amelioration is not observed by the midway point in CPT-A, a change in therapeutic approach appears warranted for preempting dropout among veterans and boosting treatment retention.