Inhibitory control underpins the relationship between cognitive and psychological inflexibility after a moderate to severe traumatic brain injury.

Cognitive flexibility is proposed as being one "building block" of psychological inflexibility/flexibility, yet empirical studies examining these associations are scarce. This study aims to examine the relationship between these constructs in those with a moderate to severe traumatic brain injury who demonstrate impairments in cognitive flexibility. A total of 66 individuals with a traumatic brain injury were administered a battery of cognitive flexibility measures in conjunction with their standard neuropsychological assessment, general (Acceptance and Action Questionnaire-II [AAQ-II]) and context-specific (Acceptance and Action Questionnaire-Acquired Brain Injury [AAQ-ABI]) measures of psychological inflexibility and psychological distress (Depression Anxiety Stress Scale-21). Linear regression modeling found the Stroop color-word interference score was the only measure of cognitive flexibility that was significantly associated with AAQ-ABI (β = -.14, p < .001), a finding that remained when controlling for Full-Scale Intelligence Quotient and education. Similarly, the Stroop color-word interference score significantly predicted the AAQ-II (β = -0.13, p = .024). Simple mediation analysis found the AAQ-ABI and AAQ-II fully mediated the relationship between the Stroop color-word interference score and psychological distress. This research provides support for the theory of cognitive flexibility being an essential component of psychological inflexibility. Inhibitory control may be an important process within cognitive flexibility that contributes to psychological inflexibility. (PsycInfo Database Record (c) 2025 APA, all rights reserved).