Introduction to Acceptance and Commitment Therapy: Theoretical, Practical, and Empirical Foundations

INTRODUCTION
Acceptance and commitment therapy (ACT) is a model of treatment organized in relation to a set of evidence-based principles designed to reduce human suffering and promote prosperity via instantiating psychological flexibility. Situated within the broad family of cognitive-behavioral therapies (CBTs), ACT builds upon previous generations and traditions within CBT to include a focus on acceptance, mindfulness, and values-based processes. Since its inception in the 1980s, the evidence for ACT has continued to grow exponentially. In light of this, ACT has been recognized by numerous health care organizations (eg, World Health Organization, American Psychological Association, and UK National Institute for Health and Care Excellence) as an empirically supported intervention for a range of conditions.

Due to its broad scope and focus on processes of change, ACT has been conceptualized as a prototype of a process-based therapy (PBT). This process-based focus means that applications of ACT have varied considerably throughout its development, while remaining true to the underlying theory. As the ACT research enterprise has matured over the past 4 decades, adaptations of ACT for a range of psychiatric disorders have emerged. Given the breadth of these clinical applications, ACT has been conceptualized as transdiagnostic in nature. As described in more detail in the forth-coming section on research support for ACT, one especially noteworthy feature of ACT’s research enterprise is that it has been applied to a number of important social issues and human challenges beyond the domain of clinical psychopathology. For example, ACT principles have been successfully used to improve workplace performance, reduce stigmatizing attitudes, decrease interpersonal partner violence, and ameliorate distress and burnout in human services workers, to name but a few of the diverse applications.

It is clear that ACT has had a substantial impact on the field of behavioral health, further cementing its status as an evidence-based intervention. While ACT embodies breadth and depth at its core, precision is also important in the sense that nuanced, in-depth applications of ACT are needed to sufficiently tailor ACT principles for particular problem areas. As such, this special issue of Psychiatric Clinics offers a collection of articles that explicate application of ACT to specific psychiatric conditions or problem areas. While much has been written over the years on the application of ACT for various mental health conditions, continued maturation and refinements in ACT theory, clinical applications, and empirical evidence of mediators and moderators suggest that an updated set of state-of-the-evidence articles in a psychiatry-specific outlet would be useful.

In the present special issue, we invited scholars with expertise in ACT as it applies to particular psychiatric areas to contribute targeted articles. While space limitations precluded an exhaustive coverage of all applications of ACT for psychiatric disorders, we chose to prioritize conditions where ACT has a reasonably robust history of research and development. We encouraged all contributors to include sections covering (a) tailored, targeted theoretic descriptions of ACT applied to the target area; (b) clinical lessons learned, including specific, nuanced adaptations to ACT needed when working with the specific population; and (c) research support for ACT in the target area, with an emphasis on treatment efficacy and processes/mechanisms of change. In service of promoting incisive, nuanced applications of ACT to particular areas, we also requested authors omit extended descriptions of the general ACT model. Instead, we reserved that task for this introductory article. In what follows, we provide an overview of ACT across the domains of theory, clinical practice, and empirical support, followed by an introduction to the special issue.