Inflexible responses to uncertainty: The mediating role of psychological inflexibility in the link between intolerance of uncertainty, traumatic stress, and somatic symptoms.

Objective: Intolerance of uncertainty (IU) and psychological inflexibility (PI) were shown to be risk factors of traumatic stress (TS) and somatic symptoms (SS) during COVID-19. The present study tested a structural equation model where PI mediated the relationships between IU, TS, and SS based on their theoretical and experimental overlaps. The contribution of all six PI facets including experiential avoidance (EA) and cognitive fusion (CF) were investigated.

Method: The sample was made up of 656 participants who reported elevated scores for TS and SS. Mediation analysis was conducted via structural equation modeling to test the proposed model. A sensitivity analysis followed the mediation analysis. Follow-up hierarchical regressions were conducted to examine the individual contribution of each PI facet.

Results: The overall model demonstrated a good fit (comparative fit index = .98; root-mean-square error of approximation = .07; total effects on TS and SS: β = .78, β = .60). IU was positively associated with TS and SS, and the relations were mediated by PI, with PI accounting for most of the effect. Hierarchical analyses revealed the less studied PI facets explained additional variance over and beyond EA and CF. EA and CF were no longer significant predictors of TS and SS after all PI facets were entered while controlling for IU and demographic variables.

Conclusions: The findings were consistent with previous researchers positing PI as an overarching construct encompassing IU and other related psychological vulnerabilities. PI facets beyond EA and CF warrant more investigations. Clinically, PI and PI facets could be important intervention targets for high IU individuals in times of uncertainty. (PsycInfo Database Record (c) 2025 APA, all rights reserved).