Combining Treatment Components in Transdiagnostic Therapy for Anxiety and Depression: A Randomized Controlled Trial

A relatively large proportion of psychotherapists endorse practicing eclectic or integrative therapy, drawing from different schools of therapy (Norcross & Alexander, 2019). This tendency towards integrative therapy has been expressed by former president of the Association of Cognitive and Behavioral Therapies, J. B. Persons, who writes: "We [clinicians] rarely proceed through a single protocol from beginning to end. Instead, we use what might be called a mix-and-match strategy, in which we select interventions or modules from one or even two or more protocols that we believe will be helpful to the patient" (Persons, 2005, p. 107). Indeed, there has been a growing research and clinical interest in personalized therapy where treatment components from different therapies are combined with the aim of targeting the symptomatology and theorized maintenance processes of the individual patient (Cohen et al., 2021; DeRubeis et al., 2014; Fisher et al., 2019; Fisher & Boswell, 2016; Hayes et al., 2022; Huibers et al., 2021; Sauer-Zavala et al., 2022). In addition to this, an increasing number of therapies are designed by combining components from different treatment models (e.g., modular and process-based therapies; Barlow et al., 2018; Hofmann & Hayes, 2019; Hofmann et al., 2021). As a result, patients are likely to be the recipients of several different techniques or strategies, based on different theoretical models, emphasizing different change principles. However, the extent to which compatibility exists between different treatment components remains an underexplored scientific question. The present study aims to fill this gap.

Combining cognitive behavioral therapies

Cognitive behavioral therapies (CBTs) are among the most well-researched psychological treatments for anxiety and depressive disorders (Cuijpers, 2017; Cuijpers et al., 2014). While CBT is often viewed as one of the major schools of psychotherapy, specific CBTs differ in their rationale and understanding of the key maintaining processes in psychopathology (Hayes, 2004). A core tenet of traditional CBT, also known as second-wave CBT, is that psychopathology is maintained by maladaptive or irrational thoughts (Beck, 1976). Thus, a commonly used therapeutic component derived from second-wave CBT is cognitive restructuring, where the patient is taught to think more realistically about emotion-evoking situations (Beck et al., 1979; Clark & Beck, 2010). Thus, cognitive restructuring can be said to target the content of thoughts.

In contrast, newer contemporary or so-called third-wave CBTs such as metacognitive therapy (MCT), acceptance and commitment therapy (ACT), and mindfulness-based cognitive therapy (MBCT) target thought processes (Hayes, 2004). A commonly used therapeutic component across third-wave CBTs involves teaching the patient to meet their experiences with mindfulness and acceptance rather than attempting to change their form (termed detached mindfulness in MCT, defusion in ACT, and decentering in MCT; Hayes et al., 2012; Segal et al., 2002; Wells, 2009). Thus, it can be argued that second- and third-wave CBTs reflect very different ways of approaching one's inner life.

Despite the differences between second- and third-wave CBTs, treatment components from each wave are often combined. One example of this is the widely employed Unified Protocol (UP) which is a transdiagnostic modular cognitive-behavioral treatment for emotional disorders (e.g., anxiety and depression) (Barlow et al., 2018). In UP, patients are asked to engage in cognitive restructuring (within the treatment module of cognitive flexibility) in one module and to practice detached mindfulness (within the treatment module of mindful emotion awareness) in another (Barlow et al., 2018). Several studies have documented that UP is an effective treatment for anxiety and depression (Longley & Gleiser, 2023). However, since the treatment modules in UP are rooted in different therapeutic traditions with different rationales, an intriguing question remains whether the treatment modules are in fact compatible. If not, then it is possible that UP is effective not because but rather despite the combination of the treatment modules (O'Toole et al., 2024).