A Short-Form Acceptance and Commitment Therapy Intervention for Intolerance of Uncertainty

Author

• Myles Charter Arendtson, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2026

Degree Name

Doctor of Philosophy

Department

Psychology

First Advisor

Lee, Eric

Abstract

Background and Objectives: Uncertainty is a ubiquitous part of human experience, can evoke a significant aversive experience, and is sometimes accompanied by the inability to endure it. Intolerance of uncertainty is a dispositional incapacity to endure the aversive response triggered by the perceived absence of salient, key, or sufficient information (Carleton, 2012). Evidence suggests that intolerance of uncertainty shares considerable thematic overlap with acceptance and commitment therapy (ACT) constructs like psychological inflexibility, fusion, and experiential avoidance (Mallett et al., 2021; Smith et al., 2020; Ümmet & Çetintaş, 2022). The current study examined how inhibitive and prospective factors of intolerance of uncertainty and ACT constructs changed following a single session ACT intervention. Method: A single-session intervention tailored to intolerance of uncertainty was delivered, and analyzed through concurrent, randomized multiple-baseline single-case experimental design (SCED). Intolerance of uncertainty, psychological flexibility, experiential avoidance, fusion, mental well-being and distress were measured via daily survey, measured across twenty days. Results: Probability of superiority analyses and meta-analyses across participants (n = 5) indicated that the intervention showed statistically significant improvements in prospective and inhibitory intolerance of uncertainty, general distress, and fusion, ranging from small to large effects. However, no statistically significant change was found in mental well-being, psychological flexibility, or experiential avoidance. Limitations: Limitations include low engagement with daily surveys and attrition, potentially attributable to delivery and sampling methods. Conclusions: Results demonstrate the preliminary efficacy of a brief ACT intervention for intolerance of uncertainty and distress and point to the need for further intervention revision to improve its feasibility and acceptability.