Psychische Flexibilität messen und im stationären Setting fördern

Background: The transdiagnostic Acceptance and Commitment Therapy (ACT)
transsituatively follows the overriding goal of promoting psychological flexibility (PF) across
various situations and settings. However, the common questionnaire-based operationalization
of PF necessary for empirical research on ACT and PF are criticized. Furthermore, only a few
studies investigating the effects of ACT on transdiagnostic samples and in inpatient settings
exist so far and further studies are needed.
Aim: In this thesis, (1) an alternative questionnaire for the assessment of PF is validated, (2)
different questionnaires for PF are compared regarding treatment sensitivity and (3) effects of
an inpatient ACT-based transdiagnostic treatment are examined.
Method: The Open and Engaged State Questionnaire (OESQ) was validated based on data of
the independent samples. The treatment sensitivity of the currently dominant PFquestionnaire
was compared to three alternative questionnaires for PF based on data of three
different samples. Finally, an observational study examined the effect of a transdiagnostic,
ACT-based inpatient treatment using pre-to-post comparisons and weekly-process-measures
from three independent sources.
Results: The OESQ showed good psychometric properties and can be highlighted in terms of
discriminatory and predictive validity compared to other PF-questionnaires. The currently
dominant PF-questionnaire showed lower treatment-sensitivity then all three other alternative
questionnaires. Finally, medium to high pre-to-post effect sizes in multiple variables and
linear increases in weekly process mesaures in PF as a result of transdiagnostic inpatient
ACT-treatment were observed.
Conclusions: As explicitly mentioned in the literature, an alternative questionnaire for PF was
developed and validated. The results regarding treatment sensitivity showed lacks in previous
assessments of PF and the results seem to suggest that possible effects of ACT regarding its
effects on PF may have been underestimated so far. Finally, the positive effects of ACT also
appear to be evident in inpatient settings and for transdiagnostic samples.