Description

Hypothesis

Personalized CBT will achieve a comparable treatment effect to the standardized CBT condition, i.e. a stronger reduction in the outcome measures (intercept and slope).

Participants

Recruitment takes place at selected university outpatient clinics throughout Germany. Patients will be recruited via the waiting list of the university's outpatient clinic, in cooperation with other currently running studies at the same university recruiting chronic pain patients, and via various media (e.g. newspaper articles) and doctors' offices. Study therapists will be recruited in the university's outpatient clinic as well. Inclusion criteria for patients are at least 18 years of age, having access to a smartphone, and the main diagnosis of chronic pain. The diagnosis will be checked using the brief version of the Diagnostic Interview for Mental Disorders (Mini-DIPS). For patients recruited via the waiting list, screening for suitability will take place during the first consultation at the university psychotherapy training center's outpatient clinic. Suitable participants will be informed about the study and referred if they agree to be contacted. Furthermore, patients that had to be excluded from other currently running studies will be referred if they agreed to be contacted as well.

Procedure & Measures:

Counterbalanced Repeated Measures Design: At this level, the primary outcome measure is pain disability index (PDI) and the WHO Disability Assessment Schedule 2.0 (WHODAS 2.0). Therapeutic alliance (Helping Alliance Questionnaire (HAQ), Working Alliance Inventory Short Revised (WAI-R); both therapist and patient version) and side effects (Negative Effects Questionnaire, NEQ) as well as expectations (Patient Questionnaire on Therapy Expectation and Evaluation, PATHEV) are collected as secondary outcome variables. These are collected before and after the diagnostic phase (A), after both interventions (C1, C2) and at follow-up (3 months). The HAQ, WAI-R, and NEQ constitute exceptions in this context. As these instruments pertain to the therapeutic relationship or the overall therapy process, they are not administered prior to the diagnostic phase, since no therapeutic contact has yet taken place. In addition, the therapist's case concept and a Perceived Causal Network (PECAN) of the therapist are collected after the diagnostic phase. Additional outcome measures are collected before the diagnostic phase (A), before the 3th baseline (B3) and at follow-up. As additional outcome measures the Depression Anxiety Stress Scale (DASS-21), the German Pain Solutions Questionnaire (PaSol), the Patient Global Impression of Change (PGIC) and Pain Self-Efficacy Questionnaire will be assed.

SCED: The participants begin with the standard diagnostic phase of routine clinical care (phase B, 5 sessions) with psychoeducation and the development of therapy goals. After a randomized baseline (phase A1, 1-3 weeks), the intervention phase (phase C) begins. Participants are randomly assigned to one of two groups. Group 1 begins with personalized CBT followed by standardized CBT whereas Group 2 begins with standardized CBT followed by personalized CBT. A second baseline takes place in both groups after the first intervention before the beginning of the second intervention (A2, randomized 1-3 weeks). After the two different therapeutic phases, another baseline (A3, 2 weeks) and afterwards an EMA phase of 3 weeks will be completed. In addition, there are two booster sessions with the therapist one and three months after the last therapy session. During the EMA phases, data will be collected 6 times per day. In all other phases, the questionnaires are asked 3 times a week.

Analysis

To evaluate group differences, a multilevel analysis (MLM) is calculated to take the nested data structure into account. The effects within the individual participant are calculated at level 1 and across the participants at level 2. To determine the required sample size, we performed a data simulation assuming a normal distribution with two predictors in the MLM: Treatment and order of treatment. The simulation revealed that a sample size of 59 participants is required, with a power of 0.80 aimed for to detect small effect sizes. Based on the dropout rate observed in a previous pilot study, a sample size of N = 75 is planned.

The Bayes Factor and visual analysis are used to continuously evaluate the intervention effect at the individual level. In the visual analysis, we look at level, trend, variability, immediacy, overlap, and consistency.