Developing an item pool to assess processes of change in psychological interventions: The Process-Based Assessment Tool (PBAT)

Process-based therapy (PBT) focuses on treatment elements that target biopsychosocial processes of relevance to individual treatment goals. This focus requires new, more integrative and idionomic models that identify key processes of change, using high temporal density measurement applied at the level of the person. Standard measurement validation approaches are inadequate to this challenge. The present study develops and provides a preliminary validation of a process-based assessment tool (PBAT) -- an item pool meant for intensive longitudinal clinical assessment. Developed using the Extended-Evolutionary Meta-Model of PBT and evaluated using a machine-learning algorithm appropriate for the evaluation of individual items, we administered the PBAT online to a sample of 598 participants (290 male; 302 female; 6 unidentified. Mage = 32.6). Analyses revealed that the PBAT distinguishes between positive and negative processes, links in theoretically coherent ways to need satisfaction and thwarting, and links to clinically relevant outcomes of sadness, anger, anxiety, stress, lack of social support, vitality, and health. The PBAT provides a beginning step towards developing a process-based tool that allows clinicians and researchers to select individual items or sets of items for individual-focused idionomic research and practice.