Explanation for the choice of comparators

Clinical guidelines of the Association of the Scientific Medical Societies in Germany (Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften, AWMF) recommend the application of evidence-based treatment manuals of CBT as standard therapy for patients with anxiety disorders [60] and depression [61]. For patients with treatment failure in the past, no specific recommendations are given, except the adaptation of treatment to possible reasons for nonresponse or, if accepted by the patient, general change in treatment modality (from psychotherapy to pharmacotherapy or reverse). Thus, based on the guidelines cited above, standard interventions for patients with treatment failures do not differ from routine care and usually comprise traditional cognitive and behavioral interventions, but not third wave therapies.

Intervention description

Both treatments comprise a 9-week baseline phase and a 20-week intervention phase.

Baseline phase

In the PBT condition, a hypothetical network model of the problem is derived, and EMA is conducted based on the key components of the model: situational context, cognition, emotion, body symptom, behavior, cognitive processing, and motivational schema. Focusing on these dimensions, typical examples of maladaptive responses are determined, and subsequently adaptive counterparts representing the desired poles of the dimensions that should be targeted in the treatment are defined. Then, participants are instructed to apply the mobile app Status (Vacay ©) which prompts the judgment of the seven dimensions established in the hypothetical network model on a bipolar scale ranging from − 100 (maladaptive) to + 100 (adaptive). Data are gathered in the situational context related to the problem. Therapists guide the adaptation of the items during the weekly sessions and help the patient to overcome difficulties in identifying situations and entering judgments of the components of the network model. EMA is completed when at least 100 measurements are taken. Then, a dynamic network analysis is computed for assessing autoregressive and cross-lagged effects of the variables [21]. These effects are estimated and visualized in a network representing variables as “nodes,” the effects between them as directed arrows (“edges”), and autoregressive effects as “self-loops.”

In the baseline phase of r-CBT, qualitative self-observational data are collected, using unstructured handwritten diaries of situations related to the problem, including notes on behaviors, cognitions, and emotions. Therapists assist patients in completing the diaries on a daily basis, support them to deepen the understanding of the problem, and derive a behavioral analysis of the individual problem based on the SORKC model according to Kanfer and Saslow (1965; [22]), as required for the application of CBT in German routine mental health care.

Treatment phase

This phase consists of 20 sessions for both treatment conditions. In PBT, treatment is initiated by a collaborative interpretation of the dynamic network model based on EMA collected during the baseline. Therapists are instructed to identify the central node, significant edges, self-loops, and positive or negative feedback loops between the nodes [19]. Based on the outcome of the dynamic network model, interventions are selected on the basis of empirical evidence for mechanisms of change matching to the central node of the individual patient, besides feedback loops and self-loops, as the key process maintaining the maladaptive pattern [10]. Interventions are conceptualized in the evolutionary framework as variation, selection, and retention of an adaptive mode of the central node related to the specific context of the problem [13]. The change of this variable is monitored using daily judgments on the basis of EMA. Further treatment planning focuses on additional targets to establish the adaptive modes of the dimensions as defined in the positive network model.

In r-CBT, as opposed to PBT, a naturalistic setting is retained for treatment decisions. Treatment planning follows traditional theories about the effects of the interventions on factors maintaining the disorder, e.g., avoidance and exposure in anxiety disorder or reduced reinforcement of activities and behavioral activation in depression [23]. Interventions are selected on the basis of common treatment manuals related to diagnoses, e.g., CBT for depression. Individual data from the behavioral analysis are used to tailor the techniques to the problem behaviors or dysfunctional thoughts of patients. Treatment process focuses mainly on the implementation of the manualized interventions adapted to the individual patient as recommended in the National guidelines for treatment of depression and anxiety disorders.

Criteria for discontinuing or modifying allocated interventions

Adverse events will be monitored by the therapists, reviewed by the supervisors and reported to the PIs throughout the trial.

Study treatment must be terminated for one of the following reasons: (a) withdrawal of patient’s consent to study treatment or (b) study treatment termination by the investigator. Study treatment of a patient will be terminated by the investigator for one of the following reasons: (a) severe serious complications which makes it necessary to stop the study treatment, including acute suicidality, or (b) non-compliance with the study protocol. If the investigator terminates the treatment of the patient prematurely, he has to inform the patient about his decision, and the primary reason for withdrawal will be recorded in the patient file. If the patient caused the premature withdrawal, the data collected before termination may be used if the patient agrees and an informed consent for follow-up is signed by the patient. Allocated interventions will be adapted on consultation of the supervisor, in case of worsening of the patient’s condition.

Strategies to improve adherence to interventions

Adherence to interventions will be supported by the strategies included in the treatment manuals. In r-CBT, these strategies include exploration of possible reasons for non-compliance, psychoeducation about the treatment, and clarification of treatment goals. In PBT, exploration of motivational factors, validation of barriers, and shared decision making in the selection of interventions will be applied.

Relevant concomitant care permitted or prohibited during the trial

Concurrent and stabilized psychopharmacological treatment will be permitted if prescribed by a psychiatrist. Concurrent psychotherapy will be prohibited and leads to exclusion from the trial.

Provisions for post-trial care

If continuation of treatment is considered as necessary by the patient and the therapist at post-treatment, patients will be offered psychotherapy in the outpatient clinic.

Outcomes Primary endpoints

Emotional distress, as assessed by the total score on the DASS-21 [25] after treatment, consisting of 20 sessions in both conditions, represents the primary outcome measure.

Secondary outcomes

Health-related quality of life will be assessed using the international standard uroqol-5D (EQ-5D; [26]). Positive mental health including emotional, psychological, and social aspects of well-being is assessed by the unidimensional Positive-Mental Health Scale (PMH, [27]) with 9 self-report items. The Anticipatory and Consummatory Interpersonal Pleasure Scale (ACIPS; [28]) is a 17-item self-report inventory and will be used to measure the pleasure patients experience in interpersonal situations. Psychological flexibility is measured by the 3-items self-report inventory Acceptance and Action Questionnaire Version 2 (AAQ-2; [29]).

The Reflective Functioning Questionnaire (RFQ; [30]) is a 54-item self-report inventory assessing the respondent’s ability to understand the internal mental states of self and others. Mentalizing capacity is divided in two subscales, Certainty and Uncertainty about mental states. The Client Satisfaction Questionnaire (CSQ-8; [31]) is an 8-item self-report instrument constructed to measure satisfaction with health services, which will be used only at post-assessment.

Weekly and daily patients’ self-ratings of treatment process

The Processed Based Assessment Tool (PBAT; [32]) is a transtheoretical set of 18 self-report items, assessing variation, selection, and retention of adaptive behavior. The Depression Anxiety Stress Scale-10 (DASS-10; [33]) is the short version of the DASS-21, a self-report inventory measuring stress, anxiety, and depression in three subscales. The Cognitive-Behavioral-Therapy Skills Questionnaire (CBTSQ; [34]) is a 6-item self-report inventory measuring patients’ use of cognitive behavioral therapy interventions, with the dimensions behavioral activation and cognitive restructuring.

The Status-PBT (Vacay ©, 2024) is a mobile application for EMA during baseline phase which uses personalized questions and captures six dimensions (thought, emotion, body sensation, behavior, cognitive processing, motivational schema) on bipolar continuous scales ranging from − 100 to + 100. Similarity of the context with typical problem situations as defined in the hypothetical network model is rated on a continuous scale ranging from 0 to + 100.

Therapists’ ratings

The Mini International Neuropsychiatric Interview [20] will be applied in the Version 7.0 for DSM-5 and contains 18 modules for the major mental disorders. At the enrolment interview, all modules will be used to assess inclusion criteria and comorbidity, but the modules anorexia and bulimia nervosa, binge eating, and prolonged grief are only carried out in full if there are indications in the interview. The presence of personality disorders is assessed according to the Structured Clinical Interview for DSM 5 for Personality Disorders (SCID-PD [35]).

A checklist of interventions for therapists is used after each session to check adherence, based on literature reviews [36, 37] and meta-analyses [38,39,40]. The Process-based Decision-making Questionnaire (PBDMQ) [24] contains 24 items and was developed to assess adherence with PBT. The “Clinical Global Impression Scale” (CGI; [41]) is 3-item observer-rated scale measuring the clinical impression of the severity of the mental disorder and is used to track changes in symptom severity.

Moderators

The Kolb Learning Style Inventory [KLSI; [42]) will be administered at pre-treatment to assess active experimentation vs. abstract conceptualization learning style. The Credibility/Expectancy Questionnaire (CEQ; [43]) comprises 6 items three items of the subscale credibility and another three items of the expectancy subscale. The Helping Alliance Questionnaire (HAQ-11; [44]) comprises 11 items and measures therapeutic alliance. The questionnaire will be completed by patients and therapists at pre- and post-treatment.

Participant timeline

Patients are evaluated by clinicians to be eligible for participation in the study on the basis of inclusion and exclusion criteria described before. If patients are eligible for treatment, they will be provided with information about the project. Patients who consent to participate in the project will be included in the pretreatment assessment (see Table 1). Patients who cannot or will not participate in the study will be offered treatment as usual in the outpatient clinic.

Table 1 Overview of measurementsSample size

Sample size estimation is based on the expected outcome in DASS-21, with treatment condition as between-subjects factor and a within-subjects repeated measurement factor (pre, post, follow-up). Since no previous trial has examined the effects of PBT, the expected effect size is set to a moderate effect of f = 0.25. Using an alpha level (α) of = 0.05 and a power of = 0.8 with correlation among repeated measures estimated at r = 0.4, 78 patients are needed (39 in each arm) to detect significant differences. To compensate for non-starters, a total sample of 80 patients will be randomized.

Recruitment

The outpatient clinic of the Department of Psychology has previously been engaged in several clinical trials. The number of attending patients is about 1000 patients per year. Thus, adequate participant enrolment can be expected to reach target sample size.