Exploration of the relationship between psychological inflexibility and psychological symptoms from a complex network perspective

The hexaflex model of psychological flexibility is a process-based transdiagnostic model of psychopathology, intervention and psychological health. According to this model psychological flexibility and inflexibility are manifest through the interactions of specific processes. This conceptualization suggests that flexibility is a dynamic and complex construct that emerges from the interplay between its constituent elements. Network modelling is suitable to explore these kind of formative constructs in mental disorders since it focuses on the relationship between components of a construct. In this regard, in the first part of this thesis (Study 1), it was aimed to adapt the Multidimensional Psychological Flexibility Inventory (MPFI; Rolffs et al., 2016), which simultaneously assesses all of the 12 processes of psychological flexibility and inflexibility, to the Turkish language and investigate its psychometric properties. The aim of the second part of this thesis (Study 2) was to apply network analysis techniques to explore the complex relationships (1) between the processes of the hexaflex model, and (2) between transdiagnostic psychopathological symptoms and psychological inflexibility. The sample of Study 1 consisted of 603 individuals (469 females, mean age= 39 years, SD = 12.3). Participants were asked to fill out Multidimensional Psychological Flexibility Inventory (MPFI), Acceptance and Action Questionnaire-II (AAQ-II) and Depression, Anxiety and Stress Scale (DASS-21) in online format. The results showed that internal consistency for the MPFI's global Flexibility scale was α = .96 and it was α = .93 for the global Inflexibility scale. Pearson's r correlation coefficient between MPFI global Inflexibility scale and AAQ-II was .73. The correlation between DASS-21 total score and the MPFI global Inflexibility scale was .66. Overall, the findings of this study showed that the Turkish version of the MPFI is a reliable and valid instrument to assess psychological flexibility and inflexibility. The sample of Study 2 consisted of 777 individuals (607 females, mean age= 36.5 years, SD = 15.6). Participants were asked to fill out Multidimensional Psychological Flexibility Inventory (MPFI) and DSM-5 Self-Rated Level 1 Cross-Cutting Symptom Measure—Adult (DSM-CC) in online format. Two regularized partial correlation networks were estimated. First one consisted of flexibility and inflexibility processes. According to the findings inaction, impulsivity or avoidant behaviors regarding valued goals ("Inaction") had the highest strength centrality. Moreover cognitive "Fusion" was identified as a key bridge between flexibility and inflexibility. The second network consisted of inflexibility processes and psychopathological symptoms. The results demonstrated that among the inflexibility processes "Inaction" had the highest Expected Influence (EI). Furthermore, cognitive "Fusion" was identified as a bridge between inflexibility and psychopathological symptoms. Overall the findings of this study showed that the components of the hexaflex model are not equally influential and instead of focusing on the many facets of this construct, clinicians might benefit from directly targeting cognitive "Fusion" and "Inaction".