Does Verbal Crystallized Intelligence Predict Efficacy of Psychological Therapies for PTSD? Results from a Randomized Controlled Trial Comparing Dialectical Behavior Therapy for PTSD (DBT-PTSD) and Cognitive Processing Therapy (CPT)

Background Treatment response in posttraumatic stress disorder (PTSD) varies widely. Intelligence has been proposed as a potential predictor, particularly in cognitively demanding interventions such as Cognitive Processing Therapy (CPT), but evidence remains limited and mixed. Objective To examine whether pretreatment verbal crystallized IQ (cIQ) is associated with treatment outcome and dropout in individuals with childhood abuse-related PTSD receiving CPT or Dialectical Behavior Therapy for PTSD (DBT-PTSD). Methods Participants ( N = 193) from a randomized controlled trial completed a verbal crystallized intelligence test (MWT-B) at baseline. PTSD severity was assessed with the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5). General linear models tested associations between cIQ and symptom reduction; probit models examined dropout. Results Higher cIQ was associated with greater PTSD symptom reduction. Post-hoc analyses indicated that this effect was primarily observed in the CPT group. No clear association was found in the DBT-PTSD group. Verbal cIQ did not predict dropout. Conclusion Verbal cIQ may be associated with treatment outcomes in cognitively demanding interventions such as CPT. If this post-hoc finding is replicated in independent studies, it will refine our understanding for whom e.g., CPT works best.