Cohort-Personality Composition’s Prediction of Treatment Outcomes in a Military Intensive Outpatient Program: A Registered Report

Intensive outpatient programs (IOPs) provide effective, accelerated therapeutic care in a cohort-based format. Although cohort dispositional characteristics (e.g., supportiveness) are theorized as meaningful to the treatment experience, their relation to treatment outcomes remains unexplored. Using longitudinal data from the Emory Healthcare Veterans Program (cohorts: N = 232; patients: N = 788; observations: N = 7,241), a 2-week IOP delivering daily individual and group-based cognitive-behavioral therapy for fear- and distress-related disorders, we tested whether cohort-personality composition (e.g., mean cohort-level Agreeableness) predicted clinical outcomes above and beyond patients’ individual traits. Variance in symptom trajectories was mostly attributable to between-persons differences (63%–73%), with modest cohort-level variability in intercepts (2%–5%) and slopes (1%–2%). All hypothesized cohort-personality effects were null. The only significant effect was cohort-level Neuroticism, which was associated with slightly higher baseline symptom severity and steeper symptom decreases during the treatment period, contrary to hypotheses.