Table 2

Secondary outcomes and corresponding measures

Secondary outcome	Measure
Transdiagnostic mechanisms of change, targeted by psychotherapeutic modules
Rejection sensitivity (module 1)	Module questionnaire: The Rejection Sensitivity Questionnaire (RSQ)24 assesses the anxious-expectations component of rejection sensitivity. The RSQ encompasses 20 hypothetical interpersonal interactions, characterised by the potential of being rejected by others. For example, patients are asked to imagine asking someone from their workplace out for coffee. Patients rate each interaction on two scales: first, they indicate their concern or anxiety that they will be rejected on a 6-point Likert scale ranging from 1 (very unconcerned) to 6 (very concerned). Then they indicate the likelihood that the other person will engage in non-rejecting behaviour toward them on a 6-point Likert scale ranging from 1 (very unlikely) to 6 (very likely). The psychometric properties of the German version have been found to be good.86
Emotion dysregulation (module 2)	Module questionnaire: The 21-item State Difficulties in Emotion Regulation Scale (S-DERS)62 allows to assess different dimensions of emotion dysregulation repeatedly over brief periods of time. The S-DERS consists of four subscales, including Non-acceptance (ie, non-acceptance of current emotions), Modulate (ie, momentary difficulties modulating emotional and behavioural reactions), Awareness (ie, limited awareness of current emotions) and Clarity (ie, limited clarity about current emotions). Patients rate statements such as “My emotions feel overwhelming” on a 5-point Likert scale ranging from 1 (not at all) to 5 (completely). Preliminary evidence supports the psychometric properties of the measure.62
Difficulties in (close) interpersonal relationships (module 3)	Module questionnaire: The 45-item Outcome Questionnaire-45 (OQ-45)87 is recommended for routine outcome monitoring in a wide range of mental health service settings.88 The OQ-45 consists of three subscales, including Symptom Distress (25 items), Interpersonal Relations (11 items) and Social Role (9 items). Patients rate statements such as “I am concerned about family troubles” on a 5-point Likert scale ranging from 0 (never) to 4 (almost always). To determine difficulties in (close) interpersonal relationships, only the OQ-45 subscale Interpersonal Relations is used, which refers to the patient’s friendships, family life and romantic relationships. The psychometric properties of the German version have been found to be acceptable to good.64
Psychopathology
Severity of personality disorder	36-item Personality Inventory for DSM-5—Brief Form Plus Modified89 and 12-item German version of the Level of Personality Functioning Scale-Brief Form 2.090, both rated by patients.
Severity of borderline personality disorder symptomatology	14-item Fragebogen zu Gedanken und Gefühlen (English: Questionnaire on Thoughts and Feelings)91 and 23-item Borderline Symptom List92, both rated by patients.
Dissociation	4-item Dissoziations-Spannungs-Skala (English: 4-item Dissociation Tension Scale),93 rated by patients.
Mentalising	20-item Certainty about Mental States Questionnaire,94 rated by patients.
Social support	5-item ENRICHD Social Support Inventory,95 rated by patients.
DZPG minimum data set	Data set designed by experts of the German Center for Mental Health (Deutsches Zentrum für Psychische Gesundheit (DZPG)) to measure core patients’ characteristics. Single items have been selected from existing questionnaires to assess socio-demographics, the exposome, dimensions of the Research Domain Criteria, Hierarchical Taxonomy of Psychopathology and everyday functioning such as mental health and quality of life. Items are rated by patients.
Clinical impression of global functioning	Clinical Global Impressions (CGI),96 two 7-point scales assessing severity of psychopathology (CGI-Severity (CGI-S)) and change since initiation of treatment (CGI-Improvement (CGI-I)), rated by therapists.
Medication	Self-designed items to assess medication before, during and at the end of treatment, rated by patients, which will allow to calculate a standardised composite psychotropic medication score following established procedures.97
Psychotherapeutic processes
Therapeutic homework	Self-designed items to assess compliance with therapeutic homework, rated by patients and therapists.
Therapeutic interventions	Self-designed Therapeutic Elements Checklist to assess the use of all therapeutic interventions in the mechanism-based modular psychotherapy (MeMoPsy) and cognitive behavioural therapy condition, including the time spent on those interventions, rated by therapists.
Continuous process monitoring
Therapeutic mechanisms	12-item Stundenbogen für die allgemeine und differentielle Einzelpsychotherapie,98 rated by patients and therapists.
Therapeutic alliance	12-item Working Alliance Inventory—Short Revised,99 rated by patients and therapists.
Symptom distress	11-item Symptom Checklist,100 rated by patients.
Mental well-being	7-item Short Warwick-Edinburgh Mental Wellbeing Scale,101 rated by patients.
Patients’ intersession experiences	Self-designed 16-item Experiences Between Psychotherapy Sessions Questionnaire, targeting intersession experiences, rated by patients.
Course of transdiagnostic mechanisms of change	12 module-specific items, taken from the RSQ, S-DERS, OQ-45 subscale Interpersonal Relations, and Reflective Functioning Questionnaire,102 to assess state aspects of changes in rejection sensitivity, emotion dysregulation, difficulties in (close) interpersonal relationships and reflective functioning, rated by patients.
Therapist-rated severity of psychopathology	Global Assessment of Functioning and Global Assessment of Relational Functioning,73 two 100-point scales rated by therapists.
Additional assessments (optional)
Ecological Momentary Assessment (EMA)	Daily prompts (29 items) which patients are asked on their smartphone at eight random times per day over a period of 1 week before treatment (ie, 7 days after T0) and at the end of treatment (ie, 1 day after T2). EMA items assess transdiagnostic mechanisms of change (ie, rejection sensitivity, emotion dysregulation, difficulties in (close) interpersonal relationships), mental, physical and social stress, and positive and negative affect. Items are self-designed or taken from the Positive and Negative Affect Schedule.103
Functional fMRI	Three experimental paradigms performed in the MRI scanner to assess neural changes post (T2) compared with pre-treatment (T0) in interpersonal threat sensitivity,104 empathy and theory of mind,67 105 and social feedback processing.106
Hormone measurements	Saliva samples to determine cortisol levels in patients. Saliva samples are collected eight times per day to calculate cortisol awakening responses and diurnal profiles on three consecutive days within the 1 week EMA period before and at the end of treatment.
Qualitative interviews	At the end of treatment, qualitative interviews are conducted with the patients and therapists in the MeMoPsy condition in order to explore the experiences made with the therapy and the assessment of its usefulness from the perspective of both. Therapists will be asked about the extent to which they have used the available interventions, their expectations concerning the implementation of tailor-made therapy for clients, and their experiences with the algorithm-driven selection of therapy modules for a population meeting different clinical diagnoses. For the selection of interview partners, either ‘maximal variation sampling‘ or ‘stratified purposeful sampling’107 is used to consider a wide range of patients and therapists (eg, age, gender, socio-economic background, previously used therapy methods, professional experience).