Evolving an idionomic approach to processes of change: Towards a unified personalized science of human improvement.

The wide variety of "third wave" cognitive behavioral therapy (CBT) methods (e.g., Acceptance and Commitment Therapy or "ACT", Compassion Focused Therapy, Meta-Cognitive therapy, Functional Analytic Therapy, Dialectic Behavior Therapy, Mindfulness-Based Cognitive Therapy) have left a mark on the field that appears to be growing. As ACT enters its 40th year, the present paper examines key features of its development strategy as a ground from which to consider the future of CBT and evidence-based therapy. We discuss four key features of ACT development: universalism, multi-level and multi-dimensional processes linked to basic principles, idiographic concepts and methods, and an evolutionary approach. We argue that these features have facilitated the development of Process-Based Therapy (PBT) and its Extended Evolutionary Meta-Model (EEMM) of processes of change, but that idiographic methods need special contemporary emphasis, because traditional methodological and statistical approaches to processes of change are based on mathematical assumptions that cannot be met and thus limit progress in this area. We argue we need to target multi-level, multi-dimensional biopsychosocial processes of change evaluated via a functional, idionomic approach that begins with frequent idiographic assessment, and then scales to nomothetic (group level) findings when it improves idiographic fit. To identify candidate processes of change, we review the world's literature on mediational findings of randomized trials of psychological interventions for mental health outcomes. After examining nearly 55,000 studies, we identify 72 measures that have successfully mediated intervention outcomes and have been replicated. The EEMM can readily summarize and understand that set of findings, and idionomic statistical methods are available to turn these processes into a new empirical form of functional analysis applicable to the individual's goals and needs. PBT frees intervention science from the unhelpful latent disease model and creates an approach that promises more rapid progress toward a unified, personalized science of human improvement.