Acceptance and Commitment Therapy-based Group Therapy for Mental Health After Stroke - a Pilot Study
Phase: NA
Conditions: Stroke, Intracerebral Hemorrhage, Depressive Symptoms, Anxiety, Stress
Sponsor: Bielefeld University

 
 
 
 
 
 
Acceptance and Commitment Therapy-based  
Group Therapy for Mental Health After Stroke –  
a Pilot Study   
Study Protocol and Statistical Analysis Plan  
12.02.2024 
 
 
 
 
 
 
 
 
 
 
Dr. Simon Ladwig (Principal Investigator) 
simon.ladwig@uni-bielefeld.de 
AE18 – Clinical Neuropsychology and Psychotherapy 
Bielefeld University, Germany 
 

Background 
Stroke is the most common cause of acquired disability in adulthood (Krishnamurthi et al., 
2020). After a stroke, every third survivor develops depression, and every fourth survivor 
develops an anxiety disorder, significantly affecting rehabilitation and quality of life (Blöchl et 
al., 2019; Kim et al., 2018; Liu et al., 2023; Rafsten et al., 2018). The most commonly studied 
psychotherapeutic approach after a stroke is cognitive-behavioral therapy (CBT), but the 
evidence for this approach’s efficacy is heterogeneous (Allida et al., 2023; Gao et al., 2016; 
Lincoln & Flannaghan, 2003). This may be attributed to inadequate adaptation to language 
and cognitive impairments and a limited fit of the CBT approach for stroke survivors 
(Kneebone, 2016; Robinson et al., 2019). 
An alternative to CBT is a modern, mindfulness-based development of behavioral therapy: 
Acceptance and Commitment Therapy (ACT). ACT principles are conveyed through metaphors, 
visualizations, and behavioral exercises. This approach does not directly aim to reduce 
psychopathology like depressive symptoms but aims to improve psychological flexibility, 
which is understood as a central resource of mental health. Pilot studies suggest the 
effectiveness of ACT in individuals with brain damage (Majumdar & Morris, 2019; Rauwenhoff 
et al., 2023; Sathananthan et al., 2022). 
Group therapies are also suitable after a stroke, as they are both economically feasible and 
implementable in neurological rehabilitation facilities. Additionally, the diversity of 
perspectives and social integration can promote mental health (Ladwig et al., 2023; 
McCracken & Gutiérrez-Martínez, 2011). 
The efficacy of ACT group therapy has not been investigated after a stroke up to now, and 
there is no German-language manual adapted for the treatment of individuals with brain 
injury. Therefore, this pilot study examines the feasibility, acceptance, and preliminary 
efficacy of an adapted ACT group therapy manual, developed in the UK and proven efficacious 
in treating individuals with brain damage (e.g., stroke, traumatic brain injury, and brain tumor 
surgeries) (Bowers et al., 2021). 
The manual was translated into German and adjusted to the needs of stroke survivors, who 
often have a higher age, more comorbidities, and specific neurological impairments compared 
to the general group of brain-damaged individuals. To reduce cognitive load and adapt to 
conventions in the German healthcare system, the session duration is shortened from 165 
minutes to 90 minutes. Additionally, the study tests outcome questionnaires translated into 
German and/or simple language for the first time to adjust them to the participants' cognitive 
capacity. 
 
 
 
 
 

Objectives 
The study aims to provide answers to the following research questions 
1. Is the group therapy program feasible? 
2. Is the group therapy program accepted by stroke survivors and therapists? 
3. Are there first indications on the efficacy of the group therapy to improve 
psychopathology and/or ACT-specific outcome measures? 
Feasibility is hereby assessed via quantitative and objective indicators in accordance with a 
previous study investigating the efficacy of ACT in people with acquired brain damage 
(Sathananthan et al., 2022).  These indicators include recruitment rates (≥ 3 participants per 
group within six months), drop-out rates ≤ 20%, group attendance ≥ 80% (out of 8 participants 
* 8 sessions = 64), homework completion rates ≥ 50% (for each session from participants 
present in session), completion rates of outcome measures ≥ 80%, treatment fidelity ≥ 80% 
(adherence to objectives and contents listed in the manual). Fidelity ratings are based on video 
recordings of two randomly selected sessions. A research assistant rates the therapists’ 
behavior according to a checklist developed for that session. 
Patients rate therapy acceptance with a validated “group therapy session questionnaire” 
(GTS-P; Zoubek, 2013), which includes six items for each session assessing for example active 
involvement and comprehensibility of contents, and two items for the entire group therapy 
on satisfaction and prospect of success. Therapists rate therapy acceptance with a co-
developed questionnaire (GTS-T) including twelve items for each session which assess the 
same six contents as the patients’ questionnaire and additional six items on the therapist’s 
involvement and satisfaction. Therapists also rate acceptance for the entire group therapy for 
each patient on six items also resembling the six items of the patient session questionnaire 
(GTS-TP).  All items are rated on a five-point Likert scale (0 = not true at all to 4 = absolutely 
true). Mean  ratings in a previous study investigating a group therapy for people with diabetes 
and depression ranged from 2.26 to 2.86 in the different versions of the questionnaire 
(Zoubek, 2013). Accordingly, a mean value higher than 2 is considered as adequate therapy 
acceptance by patients and therapists in this study.  
  
Preliminary efficacy is evaluated both via reducing of psychopathological symptoms and 
increasing of ACT-specific outcomes. ACT aims to improve psychological flexibility, which itself 
consists of the six processes present in the moment, acceptance, cognitive defusion, self-as-
context, values and committed action (Hayes, 2016). In addition to the overall construct of 
psychological flexibility, the subconstructs valued living and self-as-context are investigated in 
this study. Valued living represents the action-focused component of commitment in ACT and 
was also reported to increase in people participating in the original group therapy program 
(Bowers et al., 2021). Self-as-context represents an ACT-specific conceptualization of the self. 
Self-concept was repeatedly demonstrated as an important determinant of mental health 
after brain injury (Ownsworth, 2014), yet self-as-context represents the so far least often 
investigated subconstruct of psychological flexibility in ACT research (Foote et al., 2023). 
Hence, we included these processes in this pilot study for the investigation of preliminary 
efficacy. 

Study Design 
The study employs a pre-post design without a control group. Consequently, there is no 
randomization or blinding to conditions. Group therapy is conducted with two groups, each 
consisting of six individuals. The therapy consists of 8 sessions, each lasting 90 minutes. A 30-
minute diagnostic examination with questionnaires, including socio-demographic and health-
related data, current psychopathology (depressive symptoms, PHQ-9; Kroenke et al., 2001; 
psychological burden, DASS-21; Lovibond & Lovibond, 1995; anxiety, GAD-7; Spitzer et al., 
2006), and ACT-specific outcomes (valued living, VQ; Smout et al., 2014; psychological 
flexibility, AAQ-ABI; Sylvester, 2011; self-as-context, SACS; Zettle et al., 2018) takes place just 
before the first session. AAQ-ABI and SACS were translated into German for the first time 
according to recommendations using independent forward and backward translations (Wild 
et al., 2005). The questionnaires PHQ-9, DASS-21, GAD-7, AAQ-ABI, VQ, and SACS were also 
translated into plain language by a professional translation service (“Office for Easy Language 
Bethel”, Bielefeld). After each session, participants and therapists rate the session using the 
GTS-P and the GTS-T, respectively. After the last session, all participants answer the same 
questionnaires as before the first session. They evaluate the entire therapy in the GTS-P and 
indicate if they would recommend the therapy to a friend with similar complaints (yes/no). 
The pre- and post-assessments are conducted by a trained assistant to exclude biases from 
the study therapists as facilitators. After the last session, therapists rate the entire therapy for 
each patient using the GTS-TP.  
In a session form, therapists also record the participation of individual persons (Yes/No) and 
the completion of homework assignments (Yes/No/Incomplete) for each session. If not 
completed or incomplete, subjective obstacles are queried and documented. This serves to 
examine feasibility regarding session adherence and homework completion (objective 1).  
 
Selection and Exclusion of Subjects 
The participants are recruited through initial consultations at the university’s 
neuropsychological outpatient clinic as well as through self-help groups and practitioners in 
the region involved in the aftercare of stroke survivors. For this purpose, information flyers 
are sent to neurological rehabilitation clinics as well as neurological, physiotherapy, 
occupational therapy, and speech therapy practices. Information and contact details for the 
study are also published on the homepage of the outpatient clinic and the research unit. 
Eligibility is evaluated by the principal investigator in an a-priori screening session using 
relative’s information as additional source, if possible. 
The study includes N = 12 adult individuals who: 
1. have experienced a stroke (ischemic infarction or intracerebral hemorrhage); 
2. report increased distress according to the DASS-21; 
3. demonstrate sufficient cognitive and linguistic abilities; and 
4. show sufficient motivation for therapy. 

Increased distress according to the DASS-21 is defined as exceeding a cutoff on at least one of 
the three subscales of the questionnaire (Depression = D > 10, Anxiety = A > 6, and Stress = S 
> 10; Nilges & Essau, 2015). In the initial consultation, the cognitive and linguistic performance 
is assessed based on the participants' self-report and, if applicable, that of a family member, 
supplemented by the external judgment of the study leader, who has extensive experience in 
clinical work with individuals with brain damage. If the participant, possibly with input from a 
family member, and the study leader agree that the person can effectively participate in and 
benefit from 90-minute group therapy sessions on a weekly basis, the criterion is considered 
fulfilled. Finally, therapy motivation is assessed by participants assuring their willingness to 
change their approach to the illness, attend sessions regularly, and complete homework 
assignments within the therapy program as fully as possible. 
Exclusion criteria are assessed based on self-report and external reports by the interested 
individual, the study leader, and possibly a family member, and include: 
1. Interaction or behavioral disorders that significantly hinder group participation (e.g., 
significantly increased irritability or apathy); 
2. Other severe psychiatric disorders (dementia, psychosis, personality disorder, intellectual 
disability); and 
3. Simultaneous psychotherapeutic or neuropsychological treatment. 
 
Treatment of Subjects 
Two study therapists lead a group, and the principal investigator serves as a therapist in both 
groups. The co-therapists are licensed psychotherapists. Table 1 provides an overview of the 
contents of the sessions and homework. 
 
Table 1. Overview of Sessions and Homework 
No. Content 
Homework 
1 
Introduction, Group Rules, Identification of 
Complaints, 
Formulation 
of 
Therapy 
Expectations, Exercise "What is in my Power?" 
(Derivation of ACT Therapy Rational) 
Deepening Therapy Rational: 
Recognizing uncontrollable things in 
daily life, associated control 
strategies, and alternative coping 
methods 
2 
Introduction to Mindfulness, Connection with 
Therapy Rational, Body Scan Exercise with 
Reflection 
Daily Body Scan Exercise, One-time 
"Mindful Meal" Exercise 
3 
Discussing the Function of Negative Emotions, 
Identifying Personal Negative Emotions and 
Daily Body Scan Exercise, One-time 
"Mindful Daily Activity" Exercise 

No. Content 
Homework 
Cognitions, Mindful Management of Unhelpful 
Experiences 
4 
Identifying Individual Complaints and Control 
Strategies as a Review, Exercise "ACT-in-a-
Nutshell" 
Daily Body Scan Exercise, One-time 
"Mindful Daily Activity" Exercise, 
Recording Activities Possible After 
Stroke 
5 
Exercise "Mindfulness of Breath," Exercise 
"Passengers on the Bus" (Cognitive Defusion, 
Values Orientation), Introduction of Values and 
Identification of Personal Values with List, 
Formulation of Initial Approach Steps 
Twice daily "Mindfulness of Breath" 
Exercise, One-time "Mindfulness for 
Sounds" Exercise, Naming Important 
Values and Initial Commitments 
6 
Development of Value-Concordant SMART Goals 
(Immediate, Short-term, Long-term) 
Twice daily "Mindfulness of Breath" 
Exercise, Completing the Worksheet 
on Values and Goals 
7 
Reflection on Values and Goals, Identification of 
Cognitive Obstacles and Helpful Cognitions in 
Goal Achievement (Value-Based Life Planning) 
Optionally daily Body Scan Exercise 
or twice daily "Mindfulness of 
Breath" Exercise 
8 
Reflection on Value-Based Life Planning and all 
Sessions, Exercise "Something Positive About..." 
Conclusion 
Guidance on Implementing Value-
Based Life Plan and Incorporating 
Mindfulness into Daily Life 
 
Assessment of Efficacy 
Study design, sample size, and application of novel questionnaire versions do not allow to 
sufficiently prove efficacy of the treatment. However, first indicators of efficacy are 
investigated by pre-/post comparisons of psychological flexibility (AAQ-ABI) and psychological 
burden (DASS-21). As secondary outcomes, changes in valued living (VQ), self-as-context 
(SACS), depressive symptoms (PHQ-9), and anxiety symptoms (GAD-7) are examined. 
Statistically significant changes are considered indicators of efficacy. In addition, number of 
participants under the cut-offs on DASS-21 (D ≤ 10, A ≤ 6, S ≤10), PHQ-9 (≤ 11), and GAD-7 (≤ 
11) before and after the therapy are assessed.  
Assessment of Safety and Adverse Events 
In the screening session, presence of dysphagia is assessed via self-report to consider and 
adjust provision of drinks and/or snacks during the group therapy for individuals with impaired 
swallowing functions. Regarding all other physical health risks, legal and university internal 
protective measures are followed. 

Severe adverse events (SAEs) are recorded after half of the sessions (end of session 4) and 
after the last session. SAEs include unplanned admissions to psychiatric ward, severe self-
mutilating behavior with threat to life, suicide attempts, and death. There is also space on the 
questionnaire to report further burdensome events. If participants miss a session without 
giving notice, therapists contact them or relatives via telephone to exclude SAEs. After 
reporting a SAE, a study therapist immediately counsels the participant on treatment options. 
In case of death, relatives are offered counseling. Reporting of an SAE leads to immediate 
pausing of the study. Each SAE is then reported to two psychotherapists who do not 
participate in facilitating the study therapy. They assess whether a causal relationship 
between the SAE and the intervention is probable. If a probable relationship is determined, 
the study is immediately terminated.  
Adverse events (AEs) are defined as an increase in documented symptoms of depression, 
anxiety, and stress, or the emergence of new symptoms by the end of therapy. Participants 
experiencing new symptoms are offered counseling on further treatment options. During the 
group therapy, participants may always approach therapists to report increased burden. 
Therapists may also decide to address suspected increase of burden in individual participants. 
In case of increased burden, participants are offered counselling on treatment options.  
 
Statistical Analysis Plan 
Missing values are replaced by multiple imputation including all assessed variables. Outliers 
are identified by visual inspection and inclusion/exclusion is decided on a case-by-case 
approach. Estimates are calculated based on 95% confidence intervals.  
Feasibility (research question 1) is assessed by frequencies fulfilling the predefined cut-offs 
(see objectives).  
The acceptance score of > 2 is evaluated by Wilcoxon-tests for one sample (one-sided) for all 
versions of the GTS (-P mean of single sessions and entire therapy, -T, and -TP). Significant 
changes in primary outcomes psychological flexibility (AAQ-ABI) and psychological burden 
(DASS-21) are assessed with Wilcoxon-tests for paired samples (one-sided); p-value is 
Bonferroni-adjusted (p = .025). Significant changes in secondary outcomes valued living (VQ), 
self-as-context (SACS), depressive symptoms (PHQ-9), and anxiety symptoms (GAD-7) are 
assessed with Wilcoxon-tests for paired samples (one-sided); p-value is Bonferroni-adjusted 
(p = .0125). Individual changes in primary and secondary outcomes are also based on reliable 
change indices with a significance level of α = .90 (one-sided). 
Sensitivity analyses examine the influence of the baseline variables age, gender, kind of stroke 
(ischemia vs. hemorrhage), current use of prescribed psychotropic drugs (yes/no), previous 
mental disorder (yes/no), and previous use of psychotherapy (yes/no) on changes in primary 
and secondary outcomes. These bivariate associations are investigated by Pearson 
correlations (for continuous covariates) and Chi² tests (for categorical covariates; p = .05, two-
sided) using the difference scores of the outcomes. Likewise, associations between therapy 
acceptance and the changes in efficacy outcomes (AAQ-ABI, DASS-21, VQ, SACS, PHQ-9 and 
GAD-7) are exploratively analyzed.  
 
 

Ethics 
All participants give written informed consent. The study was approved by the ethics review 
board of Bielefeld University (EUB-2023-341).  
 
References 
 
Allida, S. M., Hsieh, C.‑F., Cox, K. L., Patel, K., Rouncefield-Swales, A., Lightbody, C. E., House, A., & 
Hackett, M. L. (2023). Pharmacological, non-invasive brain stimulation and psychological 
interventions, and their combination, for treating depression after stroke. The Cochrane 
Database of Systematic Reviews, 7(7), CD003437. 
https://doi.org/10.1002/14651858.CD003437.pub5 
Blöchl, M., Meissner, S., & Nestler, S. (2019). Does depression after stroke negatively influence 
physical disability? A systematic review and meta-analysis of longitudinal studies. Journal of 
Affective Disorders, 247, 45–56. https://doi.org/10.1016/j.jad.2018.12.082 
Bowers, H., Hill, G [Geoffrey], Webster, A., & Bowman, A. R. (2021). Living well with neurological 
conditions: Clinical outcomes, insights and reflections on three years of Acceptance and 
Commitment Therapy group intervention. The Neuropsychologist, 1(12), 33–42. 
https://doi.org/10.53841/bpsneur.2021.1.12.33 
Foote, H., Bowen, A., Cotterill, S., Hill, G [Geoff], Pieri, M., & Patchwood, E. (2023). A scoping review 
to identify process and outcome measures used in acceptance and commitment therapy 
research, with adults with acquired neurological conditions. Clinical Rehabilitation, 37(6), 
808–835. https://doi.org/10.1177/02692155221144554 
Gao, J., Lin, M., Zhao, J., Bi, S., Ni, Z., & Shang, X. (2016). Different interventions for post-ischaemic 
stroke depression in different time periods: A single-blind randomized controlled trial with 
stratification by time after stroke. Clinical Rehabilitation, 31(1), 71–81. 
https://doi.org/10.1177/0269215515626232 
Hayes, S. C. (2016). Acceptance and commitment therapy: The process and practice of mindful change 
(2. ed.). Guilford Press.  
Kim, E.‑S., Kim, J.‑W., Kang, H.‑J., Bae, K.‑Y., Kim, S.‑W., Kim, J.‑T., Park, M.‑S., Cho, K.‑H., & Kim, J.‑M. 
(2018). Longitudinal impact of depression on quality of life in stroke patients. Psychiatry 
Investigation, 15(2), 141–146. https://doi.org/10.30773/pi.2017.10.11 
Kneebone, I. I. (2016). Stepped psychological care after stroke. Disability and Rehabilitation, 38(18), 
1836–1843. https://doi.org/10.3109/09638288.2015.1107764 
Krishnamurthi, R. V., Ikeda, T., & Feigin, V. L. (2020). Global, regional and country-specific burden of 
ischaemic stroke, intracerebral haemorrhage and subarachnoid haemorrhage: A systematic 
analysis of the Global Burden of Disease Study 2017. Neuroepidemiology, 54(2), 171–179. 
https://doi.org/10.1159/000506396 
Kroenke, K [K.], Spitzer, R. L [R. L.], & Williams, J. B. (2001). The PHQ-9: Validity of a brief depression 
severity measure. Journal of General Internal Medicine, 16(9), 606–613. 
https://doi.org/10.1046/j.1525-1497.2001.016009606.x 
Ladwig, S., Werheid, K., Südmeyer, M., & Volz, M. (2023). Predictors of post-stroke depression: 
Validation of established risk factors and introduction of a dynamic perspective in two 
longitudinal studies. Frontiers in Psychiatry, 14. https://doi.org/10.3389/fpsyt.2023.1093918 

Lincoln, N. B., & Flannaghan, T. (2003). Cognitive behavioral psychotherapy for depression following 
stroke: A randomized controlled trial. Stroke, 34(1), 111–115. 
https://doi.org/10.1161/01.STR.0000044167.44670.55 
Liu, L., Xu, M., Marshall, I. J., Da Wolfe, C., Wang, Y., & O’Connell, M. D. L. (2023). Prevalence and 
natural history of depression after stroke: A systematic review and meta-analysis of 
observational studies. PLoS Medicine, 20(3), e1004200. 
Lovibond, P. F., & Lovibond, S. H. (1995). The structure of negative emotional states: Comparison of 
the Depression Anxiety Stress Scales (DASS) with the Beck Depression and Anxiety 
Inventories. Behaviour Research and Therapy, 33(3), 335–343. https://doi.org/10.1016/0005-
7967(94)00075-U 
Majumdar, S., & Morris, R. (2019). Brief group-based acceptance and commitment therapy for stroke 
survivors. British Journal of Clinical Psychology, 58(1), 70–90. 
https://doi.org/10.1111/bjc.12198 
McCracken, L. M., & Gutiérrez-Martínez, O. (2011). Processes of change in psychological flexibility in 
an interdisciplinary group-based treatment for chronic pain based on Acceptance and 
Commitment Therapy. Behaviour Research and Therapy, 49(4), 267–274. 
https://doi.org/10.1016/j.brat.2011.02.004 
Nilges, P., & Essau, C. (2015). Die Depressions-Angst-Stress-Skalen: Der DASS - ein 
Screeningverfahren nicht nur für Schmerzpatienten [Depression, anxiety and stress scales : 
DASS-A screening procedure not only for pain patients] [Depression, anxiety and stress 
scales: DASS--A screening procedure not only for pain patients]. Schmerz, 29(6), 649–657. 
https://doi.org/10.1007/s00482-015-0019-z 
Ownsworth, T. (2014). Self-identity after brain injury (1st ed.). Neuropsychological rehabilitation: A 
modular handbook. Psychology Press.  
Rafsten, L., Danielsson, A., & Sunnerhagen, K. S. (2018). Anxiety after stroke: a systematic review and 
meta-analysis. Journal of Rehabilitation Medicine, 50(9), 769–778. 
Rauwenhoff, J. C. C., Bol, Y., Peeters, F., van den Hout, A. J. H. C., Geusgens, C. A. V., & van 
Heugten, C. M. (2023). Acceptance and commitment therapy for individuals with depressive 
and anxiety symptoms following acquired brain injury: A non-concurrent multiple baseline 
design across four cases. Neuropsychological Rehabilitation, 33(6), 1018–1048. 
https://doi.org/10.1080/09602011.2022.2053169 
Robinson, P. L., Russell, A., & Dysch, L. (2019). Third-wave therapies for long-term neurological 
conditions: A systematic review to evaluate the status and quality of evidence. Brain 
Impairment, 20(1), 58–80. https://doi.org/10.1017/BrImp.2019.2 
Sathananthan, N., Dimech-Betancourt, B., Morris, E., Vicendese, D., Knox, L., Gillanders, D., Das 
Nair, R., & Wong, D. (2022). A single-case experimental evaluation of a new group-based 
intervention to enhance adjustment to life with acquired brain injury: Valiant (valued living 
after neurological trauma). Neuropsychological Rehabilitation, 32(8), 2170–2202. 
https://doi.org/10.1080/09602011.2021.1971094 
Smout, M., Davies, M., Burns, N., & Christie, A. (2014). Development of the Valuing Questionnaire 
(VQ). Journal of Contextual Behavioral Science, 3(3), 164–172. 
https://doi.org/10.1016/j.jcbs.2014.06.001 
Spitzer, R. L [Robert L.], Kroenke, K [Kurt], Williams, J. B. W., & Löwe, B. (2006). A brief measure for 
assessing generalized anxiety disorder: The GAD-7. Archives of Internal Medicine, 166(10), 
1092–1097. https://doi.org/10.1001/archinte.166.10.1092 
Sylvester, M. (2011). Acceptance and Commitment Therapy for improving adaptive functioning in 
persons with a history of pediatric acquired brain injury [Doctoral thesis]. University of 
Nevada, Reno.  

Wild, D., Grove, A., Martin, M., Eremenco, S., McElroy, S., Verjee-Lorenz, A., & Erikson, P. (2005). 
Principles of good practice for the translation and cultural adaptation process for patient-
reported outcomes (PRO) measures: Report of the ISPOR task force for translation and 
cultural adaptation. Value in Health, 8(2), 94–104. https://doi.org/10.1111/j.1524-
4733.2005.04054.x 
Zettle, R. D., Gird, S. R., Webster, B. K., Carrasquillo-Richardson, N., Swails, J. A., & Burdsal, C. A. 
(2018). The Self-as-Context Scale: Development and preliminary psychometric properties. 
Journal of Contextual Behavioral Science, 10, 64–74. 
https://doi.org/10.1016/j.jcbs.2018.08.010 
Zoubek, K. (2013). Prozessevaluation einer kognitiv- verhaltenstherapeutischen Gruppentherapie bei 
Diabetes und Depression [Process evaluation of a cognitive-behavioral group therapy for 
diabetes and depression]: Entwicklung und Validierung der Patienten- und Therapeuten-
Gruppentherapiestundenbögen (GTS-P, GTS-T, GTS-TP) zur Vorhersage des Therapieerfolgs 
[Development and validation of the patient and therapist group therapy questionnaires (GTS-
P, GTS-T, GTS-TP) for predicting therapy success] [Doctoral thesis]. Johannes Gutenberg-
Universität, Mainz.