Probing the relative psychometric validity of three measures of psychological inflexibility

The present study probed the relative structural and concurrent validity of responses to three self-report measures of psychological inflexibility with a large sample of college students (N = 797): the revised version of the Acceptance and Action Questionnaire (AAQ-II), the shorter version of the Avoidance and Fusion Questionnaire for Youth (AFQ-Y8), and the longer version of the Avoidance and Fusion Questionnaire for Youth (AFQ-Y17). Structural validity findings showed that responses to the AAQ-II and AFQ-Y8 indicated good data-model fit and latent construct reliability, whereas the data-model fit for responses to the AFQ-Y17 was poor, despite strong latent construct reliability. Concurrent validity findings demonstrated that scores derived from all three measures of psychological inflexibility had comparable correlations with several concurrent indicators of negative mental health (i.e., depression, anxiety, global negative affect), positive mental health (i.e., happiness, hope, global positive affect), and theoretically-similar therapeutic processes (i.e., mindfulness skills). Yet findings from hierarchical regressions evidenced some incremental validity when scores from the AAQ-II, AFQ-Y8, and AFQ-Y17 were taken together to predict concurrent mental health outcomes-suggesting potential differential construct representation among these three measures. Limitations of the present study and future directions for research and practice are discussed.