What this is
- This protocol outlines a randomized controlled trial comparing cognitive behavioural therapy (CBT) combined with () against CBT alone for patients with .
- The study targets 156 outpatients diagnosed with depression or anxiety disorders who experience significant interpersonal difficulties.
- The aim is to evaluate the efficacy and feasibility of in improving interpersonal skills and reducing distress.
Essence
- The trial investigates whether adding to standard cognitive behavioural therapy enhances treatment outcomes for patients with . It aims to show greater reductions in interpersonal distress and symptom severity compared to CBT alone.
Key takeaways
- The study includes 156 patients with a primary diagnosis of depression or anxiety and significant . Participants will receive either CBT alone or CBT plus .
- consists of 12 weekly group sessions, focusing on improving interpersonal skills through modules like nonverbal communication and conflict resolution.
- The primary outcome is the change in interpersonal distress, assessed using the Inventory of (IIP-32) from baseline to post-assessment.
Caveats
- The study relies on self-reported measures, which may introduce bias. Additionally, the results may not be generalizable beyond the specific patient population studied.
Definitions
- Interpersonal Problems: Difficulties in relationships that persistently cause distress, often linked to various psychiatric conditions.
- Kiesler Circle Training (KCT): A group intervention designed to improve interpersonal skills through structured training modules.
Simplified
Introduction
In recent decades, there has been a shift in the conceptualisation of mental disorders. Moving away from a categorical approach centred on discrete diagnostic groups, the field has adopted a transdiagnostic perspective advocating for a dimensional understanding of psychopathology.1 The categorical approach, notably used by the current Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the International Classification of Diseases (ICD-11), proposes a group of symptoms to define specific disease entities. In this framework, symptoms are seen as manifestations of an underlying common cause, which requires disorder-specific interventions.2 However, the categorical approach fails to account for the high comorbidity rates observed across disorders3 and does not explain why disorder-specific treatments often lead to improvements in symptoms that were not the primary focus of the intervention.4 5
In contrast, the transdiagnostic approach argues that many disorders share key etiological processes that transcend traditional diagnostic boundaries, with the interplay of these processes playing a causal role in the emergence and maintenance of psychopathology across diagnostic categories. The transdiagnostic approach calls for innovative and effective treatment strategies6 7 that target the various domains of transdiagnostic processes, including attention, memory, reasoning, thought and behaviour.8
Interpersonal problems
The present study focuses on interpersonal functioning as a key transdiagnostic process within the behavioural domain. Interpersonal problems are defined as difficulties that occur persistently and repetitively in relationships with others and cause distress.9 Interpersonal problems are by definition a hallmark of personality disorders, but they also manifest across a range of other psychiatric conditions. Patients with psychiatric diagnoses experience significantly more interpersonal difficulties than healthy reference groups10 and report higher levels of general distress in social interactions.11 These difficulties are a small but robust negative predictor of psychotherapy outcomes.9 As such, addressing interpersonal issues within therapy is likely to enhance overall therapeutic effectiveness.
Deficits in interpersonal functioning have been linked to early maladaptive interactions with significant others. Child maltreatment, especially emotional abuse and neglect,12 is a well-established predictor of depression and anxiety.13 14 It is closely associated with heightened interpersonal difficulties,15 16 likely due to its impact on the ability to form and maintain healthy relationships in adulthood.17 According to a recent meta-analysis, child maltreatment is associated with lower global social functioning (r = −0.11 to −0.20) and poorer interpersonal relations (r = −0.18 to −0.33).18 While the impact of child maltreatment on the course of treatment remains inconclusive,19 20 there is evidence that psychotherapeutic approaches that consider the biographical background are particularly effective. Patients with distinct patterns of emotional neglect and abuse demonstrated better treatment outcomes with the Cognitive Behavioral System of Psychotherapy (CBASP) compared with non-specific supportive psychotherapy.21 These findings emphasise the importance of psychotherapeutic interventions addressing the interpersonal impact of child maltreatment, such as those applied in the Kiesler Circle Training (KCT).
Improving interpersonal skills: the Kiesler Circle Training (KCT)
The KCT is based on an empirically derived structural model used to organise interpersonal functioning within the Contemporary Integrative Interpersonal Theory (CIIT).22 This model arranges the variety of interpersonal behaviours in terms of a circular continuum allocated on two orthogonal axes: the vertical axis addresses interpersonal control (agency), which ranges from dominant to submissive behaviour, whereas the horizontal axis addresses interpersonal communion, which ranges from friendliness to hostility (figure 1). The circumplex model allows illustrating complementary action tendencies to anticipate others’ reactions and to guide one’s own behaviour to achieve interpersonal goals. Patients with anxiety and depression are often associated with a rigid pattern of socially avoidant interpersonal behaviour,23 24 referring to low agentic and low communal behaviours. KCT is designed for increasing the awareness of interpersonal action tendencies and for improving interpersonal behavioural flexibility. It is based on the individual biographical background, the so-called significant-other history, and targets corrective interpersonal experiences against former interpersonal experiences of child maltreatment. KCT originated from CBASP,25 but was adopted and manualised for the group setting.26 In a phase I study conducted in an inpatient CBASP setting, patients with the primary diagnosis of persistent depressive disorder along with high rates of interpersonal problems and child maltreatment demonstrated reduced interpersonal problems after 12 weeks of treatment including weekly KCT group sessions.27 The reduction of interpersonal problems was moreover significantly associated with the reduction of depression severity (r=0.57). However, the homogeneous patient group, the inpatient setting and the absence of a control group limit the interpretation regarding the efficacy and feasibility of KCT as transdiagnostic group intervention.
Kiesler’s circumplex model. The x axis depicts communion; y axis depicts agency. Arrows illustrate interpersonal action tendencies.
Aims and hypotheses
The present study aims to investigate the efficacy and feasibility of a transdiagnostic GRroup intervention for improving InterPersonal Skills (study acronym: GRIPS), the KCT, by comparing individual, state-of-the-art cognitive behavioural therapy (CBT) augmented by KCT group sessions with individual CBT only in patients with a categorical diagnosis of either depression or anxiety and significant interpersonal problems. Interpersonal distress represents the primary outcome. Considering the widespread prevalence of interpersonal problems across various categorical diagnoses, including mood disorders, anxiety and phobic fears, psychosis, substance use disorders, eating disorders and personality disorders,10 11 28 the reduction of interpersonal distress is supposed to accompany symptomatic change of the respective categorical diagnosis. The main hypotheses are:
The study will also examine secondary hypotheses related to moderating and mediating effects on interpersonal functioning. Specifically, we will test the hypothesis that the impact of KCT on reducing interpersonal problems is moderated by experiences of child maltreatment, with individuals reporting higher levels of maltreatment benefiting more from the intervention. Additionally, we hypothesise that the quantity and quality of daily social interactions mediate these improvements.
Methods and analysis
Study design
This prospective randomised controlled phase II trial (RCT) compares two active conditions: CBT in individual sessions augmented by 12 weekly KCT group sessions (experimental group, CBT+) versus CBT in individual sessions only (control group, CBT). Individual patients will be randomised 1:1 to each condition, with randomisation conducted separately at each study centre and stratified by primary diagnosis (depression or anxiety) to ensure balanced group distribution. The allocation sequence will be generated using computer-generated random numbers. The study will be conducted at the Centre for Psychological Psychotherapy (ZPP) at the University of Greifswald, Germany, and the Institute for Integrative Psychotherapy Training (IPB) at the Medical School Berlin, Germany. Both sites will conduct CBT+ and CBT only in an outpatient setting. After study inclusion, patients will be assessed at baseline (T1, weeks 1–2), mid-treatment (T2, week 8), post-treatment (T3, week 14) and follow-up (T4, 3 months later).
Study population and recruitment
156 patients with a categorical diagnosis of either a depressive or an anxiety disorder according to DSM-5 and significant interpersonal problems (one SD above the German norm according to Thomas et al29) will be recruited. Patients eligible for the trial must comply with the following inclusion criteria at randomisation:
Key exclusion criteria are the following:
Study inclusion is possible at any point during the course of ongoing individual CBT. To ensure sufficient patient recruitment in the planned period of 20 months, the study will be regularly announced in person and by flyers and newsletters.
To lower dropouts, patients randomised to the control group will be offered to join the KCT group therapy after completion of the FU assessment (T4). These patients will be asked to answer the evaluation forms for the KCT modules, which will increase the amount of feedback that contribute to the improvement of the KCT manual for a future study. Moreover, all patients will get an expense allowance for taking part in the assessments at T2 and T4.
Sample size
The sample size calculation is based on Holgersen et al,30 who argue that a clinical significance can only be assumed with an effect size of Cohen’s d=0.5, considering the costs of implementing an additional group therapy. Our sample size calculation relies on a two-tailed two-sample t-test, while a baseline-adjusted analysis of covariance (ANCOVA) will be used for the primary efficacy analysis. This results in a higher power compared with the two-sided t-test, which ignores the influence of different baseline values. This strategy for calculating the sample size is a conservative procedure. With a two-sided t-test with equal variance, the power analysis resulted in a group sample size of 64. This sample size achieves a power of 80% for rejecting the null hypothesis of equal means at a significance level (alpha) of 0.05. Considering approximately 17% dropouts during the treatment phase based on our phase I study,26 the total number of patients to be recruited is 156 (78 per group). Consequently, approximately 250 patients will undergo eligibility screening using diagnostic tools (see figure 2).
Trial design. CBT, cognitive behavioural therapy; KCT, Kiesler Circle Training; T1, baseline; T2, mid-assessment; T3, post-assessment; T4, follow-up.
Outcome measures
Change in interpersonal distress by self-report from baseline (T1) to post-assessment (T3) represents the primary outcome (Hypothesis 1). Interpersonal distress will be assessed by the IIP-32,29 a short version of the original IIP-D.31 Individuals have to rate the extent to which a number of behaviours, thoughts and feelings in social interactions pose difficulties for them on 32 Likert-scaled items that range from 0 (not at all) to 4 (absolutely). The mean score of all items indicates the general level of interpersonal distress; higher values represent more severe interpersonal problems. The IIP-32 shows a high validity29 and a satisfactory sensitivity to change.32
Symptom severity changes with regard to the primary diagnosis (Hypothesis 2) from T1 to T3 will be assessed by independent and trained raters who are blinded for treatment assignment. Patients are advised not to reveal any information that might indicate their group assignment during the trial visits. In case the group assignment is revealed, a back-up rater will conduct the pending trial visits. For patients with a primary anxiety disorder, the 14-item version of the Hamilton Anxiety Rating Scale (HAM-A) will be investigated. For patients with a primary depressive disorder, the 24-item version of the Hamilton Rating Scale for Depression (HAM-D) will be used. HAM-A and HAM-D are semistructured interviews with good psychometric qualities33 34 that measure the severity of all symptom domains of anxiety and depression described by the DSM over the last 7 days. Change sum scores from pre-assessment (T1) to post-assessment (T3) will be standardised into z-values so that HAM-A and HAM-D scores can be combined for the analysis. The reliable change index (RCI) will be calculated to assess whether difference scores can be considered clinically meaningful.
Child maltreatment will be assessed as moderator of change using the Childhood Trauma Questionnaire.35 Ecological Momentary Assessment (EMA) will be used to identify mediators of change in interpersonal functioning and symptom severity. EMA involves collecting real-time data in the natural environment of participants via smartphones, allowing to capture the dynamics of interpersonal behaviour and emotional states as they unfold.36 In this study, data will be collected four times per day at random intervals. At each assessment, participants will report on core characteristics of their behaviour (quality of social interactions) in their most recent social interaction, the number of social interactions since the last assessment (quantity of social interactions), and their affective state. Participants can decide whether to consent to smartphone data collection and join the additional GRIPS-EMA study. This decision will not affect their continued participation in the GRIPS study.
A comprehensive overview of the frequency and scope of all trial visits is depicted in table 1. Table 2 summarises primary and secondary outcomes with its corresponding measures. Exploratory outcomes are summarised in a supplementary table (see onlinesupplemental tables 12).
| Screening | Baseline | Intervention | FU | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Trial visits | T0 | T1 | T2 | T3 | T4 | ||||
| Week | 0 | 1–2 | 4 | 6 | 8 | 10 | 12 | 14 | 26 |
| Informed consent | X | ||||||||
| Inclusion/exclusion criteria | X | ||||||||
| SCID-5-CV | X | ||||||||
| SCID-5-PD | X | ||||||||
| Demographic information (OR) | X | ||||||||
| Randomisation 1 | X | ||||||||
| Primary outcome | |||||||||
| IIP-32 (SR) | X | X | X | X | X | ||||
| Secondary outcome | |||||||||
| Symptom severity (OR)—depression: HAM-D—anxiety: HAM-A | X | X | X | X | |||||
| Moderator of change | |||||||||
| CTQ (SR) | X | ||||||||
| Mediator of change | |||||||||
| EMA | X | X | X | ||||||
| Exploratory outcome | |||||||||
| Symptom severity (SR) depression: BDI-V, anxiety: BCQ and ACQ | X | X | X | X | |||||
| IMI-R (OR) | X | X | X | ||||||
| IIM (SR) | X | X | X | ||||||
| SEDI (SR), PHQ (SR) | X | X | X | ||||||
| WHOQoL-BREF (SR) | X | X | X | ||||||
| PID5BF+ (SR) | X | X | X | ||||||
| LPFS-BF (SR) | X | X | X | ||||||
| CAMSQ (SR) | X | X | |||||||
| Adverse events and side effects | |||||||||
| Medication 1 | X | X | X | ||||||
| Side effects (INEP) | X | ||||||||
| NUGE-24 (CBT+KCT only) | X | X | X | ||||||
| Outcome measure | Measure description |
|---|---|
| Primary outcome | |
| Inventory of Interpersonal Problems (german version): IIP-32 [29] [43] | The IIP-32 is a self-report form for interpersonal problems based on Horowitz's Circumplex Model. It consists of 32 items that assess difficulties in interacting with others on a 5-point Likert scale (0=not at all, 4=very much). |
| Secondary outcomes | |
| Hamilton Depression Rating Scale, 24 items version HAM-D [44] | The HAM-D is a semistructured interview, which measures the severity of depressive symptoms experienced in the last week. Blinded and trained study raters will assess the severity of symptoms for each of the 24 items using a scale ranging from 0 to 2, 0–3, or 0–4. The total score ranges from 0 to 75, with higher scores indicating a higher severity of depression. |
| Hamilton Anxiety Rating Scale HAM-A [34] | The HAM-A is a semistructured interview, which measures the severity of anxiety symptoms experienced in the last week. Blinded and trained study raters will assess the severity of symptoms for each of 14 items using a 5-point scale ranging from 0 to 4. The total score ranges from 0 to 56, with higher scores indicating a higher severity of anxiety. |
| Other outcome measures (moderation and mediation) | |
| Childhood Trauma Questionnaire (german version): CTQ [35] [45] | Child maltreatment is assessed as a main moderator at baseline. The CTQ is a self-report assessment designed to measure experiences of child trauma and abuse on five subscales (emotional abuse, physical abuse, sexual abuse, emotional neglect and physical neglect). Patients rate the frequency of 34 of these experiences on a 5-point scale (1=not at all, 5=very often), and each subscale score has a range from 5 to 25 points. Higher scores indicate a higher severity in child trauma. |
| Quality and quantity of daily social contacts | Patients answer short questionnaires four times a day, which appear on their smartphone at random times (Electronical Momentary Assessment, EMA). The number of social contacts, the quality of social contacts (interpersonal complementarity), interaction partner, affect and anxiety are assessed. |
Interventions
Experimental intervention: KCT
The KCT is a transdiagnostic group therapy developed for patients with interpersonal problems.26 27 Within the framework of this study, KCT will be investigated as augmentation of individual state-of-the-art CBT. KCT consists of 12 sessions of 100 min each in a group of up to 10 patients. One individual session of 100 min will be conducted before the beginning of the group with one of the two group therapists, both to establish a working alliance, given the concerns and worries patients with interpersonal problems might have before entering the group, and to develop a so-called individual transference model to anticipate upcoming interpersonal problems. This model assumes that negative experiences with significant others from the past translates into patients’ expectations about what is likely to happen in current social interactions. Therapists help their patients to (a) identify their individual interpersonal problems, (b) connect their past experiences with others to their present interpersonal fears (transference hypotheses) and (c) define individual treatment goals for the group sessions. The group therapy comprises five modules: (a) getting to know the interpersonal circle, (b) nonverbal communication, (c) verbal communication, (d) conflict training, (e) empathy and corrective interpersonal experiences. Group sessions are manualised but designed flexibly in a way that some interventions in each module are mandatory while others are flexible (box 1). All modules comprise both psychoeducative elements and experience-activating methods, such as role-play, to actively acquire and train interpersonal skills.
Control intervention: CBT
Modern, state-of-the-art individual CBT serves as the control intervention. At its core, CBT is based on the interaction between thoughts, emotions and behaviour. Individual CBT for depression and anxiety primarily focuses on intrapersonal therapeutic areas, such as identifying and modifying dysfunctional thoughts, promoting behavioural activation, conducting fear exposure, implementing behavioural experiments or teaching relaxation skills. Additionally, it may address interpersonal areas, such as social skills training and enhancing social competence. Modern, state-of-the-art CBT also integrates concepts from the so-called ‘third wave’ of therapy, including the exploration of negative schemas, skills acquisition, mindfulness or acceptance-based strategies. In line with the categorical approach, disorder-specific treatment manuals are available for all diagnoses included in the study. However, state-of-the-art CBT does not necessarily entail strict adherence to a manual. Since both study sites are CBT training institutes that ensure supervision at least every 4 hours, it can be reasonably assumed that modern, state-of-the-art CBT is being implemented. Individual therapists will be asked to document the interventions used in each session via a checklist.
Adherence
Study therapists at both study sites are graduated psychologists who are at an advanced stage of postgraduate psychotherapy training. Study therapists who guide KCT participated in a full-day workshop in which the KCT modules were trained according to the group manual and challenging interpersonal situations within the group were trained by demonstration and role-play. Before treating study patients with KCT, therapists must meet specific competence criteria based on the CBASP adherence rating regarding the therapeutic relationship. These criteria include collaboration, therapeutic empathy towards the patient, effective listening, appropriate control, tolerance of negative affects, and the use of therapeutic self-disclosure when appropriate. Competence is assessed by evaluating a videotaped individual session in which a patient’s individual transference model is developed. The results of the rating are discussed in an individual supervision session before the start of group therapy, and, if necessary, modifications for behaviour change are identified and developed. After that, biweekly group supervision is mandatory for study therapists to ensure treatment adherence. KCT group sessions will be videotaped for supervision.
Data management and monitoring
Study data will be entered in pseudonymised form in a study database by authorised and trained members of the study team via electronic case report forms (eCRF). Self-reports are entered automatically into eCRF by patients. Data capture and data management will be performed using the study software SecuTrial (interActive Systems, Berlin) provided by Charité. SecuTrial features remote web-based data capture and real-time monitoring. The software has been designed to meet the requirements of the FDA (21 CFR Part 11) and the guidelines for Good Clinical Practice.
Statistical analysis
The analyses of the primary and secondary endpoints will be performed by a statistician blinded to treatment allocation. Statistical analysis will be performed according to the intention-to-treat principle and longitudinal dropouts will be handled via multiple imputation. Regarding the first hypothesis, primary analysis will consist of an ANCOVA for the treatment effect (time by group), adjusted for interpersonal distress at baseline, the number of individual sessions between T1 and T3, and treatment site. Regarding the second hypothesis, that is, mediation of the treatment effect in primary diagnosis by reductions in interpersonal distress, longitudinal structural equation models will be applied for disentangling causal effects. Here, measurements taken at T2 will serve as intermediate measurement. To test the moderator hypothesis about child maltreatment, a further ANCOVA will be conducted, including interaction effects. Sensitivity analysis will be conducted for the observed sample as well as the per-protocol cohort. The EMA data collected as part of the study will be analysed using latent growth curve models, which allow for the examination of longitudinal developmental processes. These models will be estimated as structural equation models, facilitating the integration of mediators into the causal model. Significance testing of the indirect mediation effect is embedded within the model, allowing a robust analysis of how real-life social interactions, as captured by EMA, mediate the effectiveness of the group intervention.
A detailed Statistical Analysis Plan will be prepared before database lock and start of the analysis.
Consent to participate
All prospective participants are informed about the opportunity to join the study through standardised informational materials at both study sites. If they express interest, a screening appointment will be scheduled, during which voluntary oral and written informed consent for study participation, as well as for the storage, evaluation and transfer of study-related data, will be obtained by research associates at the respective study centre. Participants will be thoroughly informed about their right to refuse participation or withdraw consent at any time, without the need to provide a reason. In the event of withdrawal of consent, participants will have the option to decide whether their data should be deleted or destroyed, or whether it can be used in anonymised form for this research project.
Safety/harms
To date, there have only been a few studies on the adverse effects of outpatient group psychotherapy including worsening of symptoms, unpleasant memories and feelings, stress, anxiety, sadness or sleep problems.37 In a previous study, KCT integrated into an inpatient CBASP framework was also examined for potential negative effects through a qualitative data analysis.27 Of the 87 patients, 41 (47%) reported negative aspects of the group therapy, which were related to structural issues within the inpatient setting, external disturbances, deficits in group cohesion, doubts about the CBASP concept, and group size. In the present study, we have addressed most of these concerns by conducting outpatient closed groups that are not part of a CBASP setting and by maintaining a stable group size with a maximum of 10 patients.
In the present trial, adverse events (AEs) are defined as (a) exacerbation of symptoms, (b) appearance of new symptoms, (c) passive suicidal thoughts and (d) active suicidal plans or intentions. Serious adverse events (SAEs) comprise (a) death or (b) any life-threatening event that requires inpatient medical treatment. AEs and SAEs are regularly documented at all trial visits. During the weekly KCT group sessions, group therapists are encouraged to carefully notice any (S)AEs and, if necessary, interview the patient using a paper-and-pencil version of the eCRF documentation. If a patient reports an (S)AE via eCRF, the patient is going to be contacted by the study team within 24 hours to assess the (S)AE in more depth regarding the circumstances, its duration (start/end date), intensity (mild, moderate, severe), assessment of causality (treatment related, probably related, unlikely related, not related, not assessable), the actions taken, and its outcome. Additionally, the patients’ individual CBT therapist will be informed. All SAEs, particularly severe adverse treatment reactions (SATRs), have to be reported to the principal and coprincipal investigators (AG, E-LB) and will be discussed with a Data Safety Monitoring Board. Suicidality and hospitalisation in reaction to the group intervention (SATR) are defined as individual stop criteria leading to discontinuation of the trial. The whole trial will be discontinued in case the study (co)principal investigators or members of the Data Safety Monitoring Board have serious ethical concerns regarding participants’ safety.
Data monitoring will be regularly conducted by a clinical monitor from CTO to ensure patients’ safety and integrity of the clinical data in adherence to the study protocol, data quality and accuracy. The process will be independent from investigators and the sponsor.
Ethics and dissemination
Positive ethical approval for the study and the study add-on with EMA was granted by the ethics committee of Charité Berlin (numbers: EA4/154/23, EA4/228/23) and the local ethics committees of the University of Greifswald and the Medical School of Berlin. The research outcomes will be disseminated through publication in international scientific journals and will also be shared with both the psychological and medical scientific communities through conference presentations.
Trial status
The study officially began in April 2023. The first patient was included in July 2024. The last patient entry is expected for March 2026 and data collection aims to be completed in September 2026.
Discussion
The transdiagnostic perspective on mental disorders has gained significant attention in clinical interventions, as demonstrated by an exponential increase in publications from 2018 (n=224) to 2023 (n=1033) (Cochrane search terms: “transdiagnostic” AND “treatment”; search date: 3 January 2024). Despite the recognised impact of social relationships on health, surprisingly few studies within this framework have focused on interpersonal functioning. Individuals who are socially isolated, are lonely or live alone are at an increased risk of premature mortality, with this risk comparable to well-established factors such as physical inactivity, obesity or substance abuse.38 The KCT provides techniques ideally suited for a transdiagnostic group intervention focusing on interpersonal problems. KCT has demonstrated its feasibility and effectiveness in improving interpersonal distress, even in challenging cases with treatment resistance, comorbidities and child maltreatment.27 We among others found that the reduction of interpersonal distress through treatment was associated with reduced depressive symptoms.2639,41 However, questions remain regarding the feasibility and efficacy of KCT in improving interpersonal problems for various diagnoses beyond persistent depressive disorder. Furthermore, it remains to be seen whether KCT will outperform the improvements achieved by individualised, state-of-the-art CBT, which is considered the gold standard in psychotherapy, despite the fact that more than half of patients do not achieve a response (eg, 42% CBT response rate in depression).42 Given that interpersonal problems can hinder therapeutic outcomes,9 it can be anticipated that an augmentation therapy focused on improving interpersonal functioning will lead to higher response rates and greater overall well-being. Unlike CBT, which addresses interpersonal functioning as one of many treatment foci, KCT delves into the individual biographical background and aims to correct interpersonal experiences through therapist and peer interactions, which is particularly significant for patients with interpersonal fears. Daily assessments of social contacts and their quality as mediators of interpersonal functioning, along with the consideration of child maltreatment as a moderator, will enhance our understanding of the impact that social interactions have on psychopathology.
Protocol amendments
The CI has the authority to modify the study protocol if necessary, even after the study has commenced. Any significant changes affecting patient safety, the scientific basis of the study, or other critical aspects will be communicated to the relevant ethics committees. The amended protocol can only be implemented after receiving a positive opinion from the ethics committee, the signature of the amendments by the original protocol signatories, and confirmation of receipt/approval of the amendments by all investigators.
supplementary material
Acknowledgements
We would like to thank Babette Renneberg and Martin Hautzinger for their contribution as independent experts and members of the Data Safety Monitoring Board. We would also like to thank Johannes Zimmermann for his support in developing the design of the ecological momentary assessments. We thank the Studienschmiede Charité and CTO-Team Berlin for their support in the application process and the study set-up.