This research examined whether a one-session acceptance-focused Acceptance and Commitment Therapy (ACT) intervention could increase psychological flexibility (PF) in university students, and whether these changes were associated with changes in state anxiety. In addition, the study explored whether the intervention effect differed across three psychological flexibility processes: openness to experience, behavioral awareness, and valued action.

A total of 102 university students were included in the final analyses and were assigned to either an acceptance-focused ACT intervention or a psychoeducation control condition. Psychological flexibility and state anxiety were measured before and after the intervention. As expected, results showed that the intervention group had a significantly greater increase in PF compared to the control group. Interestingly, no direct effect of the intervention was found on state anxiety, suggesting that the intervention effect did not translate to a decreased state anxiety. However, there was found an indirect effect of the intervention on state anxiety through PF, which could be relevant to further invest in future research. Lastly, no statistically significant evidence was found that the intervention affected one PF process more strongly than others. However, power was initially too low to research this and the descriptive pattern suggested that openness to experience may have been most responsive to the intervention, which shows relevance for future research. 

In conclusions, these findings suggest that a brief acceptance-focused ACT intervention may be a promising approach for increasing psychological flexibility, while future research should further examine its relationship to state anxiety and the differences among PF processes.