UC San Diego

Acceptance and Commitment Therapy (ACT) is a third-wave cognitive-behavioral treatment that targets psychological flexibility (PF), or the ability to persist in behavior consistent with values regardless of unwanted private experiences. The growing use of ACT necessitates an accurate assessment of PF. The Comprehensive Assessment of Acceptance and Commitment Therapy (CompACT) is a three-factor measure of PF (Openness to Experience, Valued Action, and Behavioral Awareness) whose psychometric properties have been examined in limited populations. The current study examined the factor structure and psychometric properties of the CompACT in U.S. military personnel who enrolled in a weight management randomized controlled trial. Military personnel who either failed or were at risk of failing the Navy's physical fitness assessment or had overweight/obese body mass index (BMI; N = 178, M_age = 29.15 years; M_BMI = 33.13 kg/m²; 61.8% female) completed the CompACT and other questionnaires. Confirmatory factor analysis was used to evaluate the three-factor structure of the original 23-item CompACT (CompACT-23) as well as an 18-item version identified in a Portuguese sample (CompACT-18). Internal consistency and convergent validity with measures of weight-related experiential avoidance, perceived stress, anxiety, depression, PTSD symptoms, and life satisfaction were examined. The three-factor structure of the CompACT-23 showed poor fit to the data while the fit of the CompACT-18 was acceptable, as indicated by three descriptive indices (χ²/df = 1.73, RMSEA = 0.069, SRMR = 0.074). All descriptive fit indices in addition to two comparative fit indices (AIC and BIC) indicated improved model fit over the CompACT-23. The CompACT-18 and its subscales exhibited adequate internal consistency (α = 0.768 to 0.861) and convergent validity in expected directions with measures of weight-related experiential avoidance, perceived stress, anxiety, depression, PTSD symptoms, and satisfaction with life. Results support using the refined, English language CompACT-18 as a three-factor measure of PF in populations such as U.S. military personnel who may benefit from weight management intervention. Future research should explore the content validity of the full measure and the removed items. Lost content could mean the CompACT-23 and the CompACT-18 differentially assess PF. Additional studies should examine psychometric properties in large and more diverse samples to further evaluate the appropriateness of the measure across populations. Longitudinal studies are needed to examine test-retest reliability and sensitivity to change.