Intolerance of Uncertainty (IU)

Abstract

The Intolerance of Uncertainty Scale (IUS) is a widely utilized self-report instrument designed to measure an individual’s dispositional tendency to react negatively—emotionally, cognitively, and behaviorally—to uncertain situations and events. Originally developed as a 27-item measure (IUS-27) by Buhr and Dugas, it operationalizes Intolerance of Uncertainty (IU) as a core cognitive factor implicated in the development and maintenance of generalized anxiety disorder (GAD) and pathological worry. A revised, shorter 12-item version (IUS-12) was later validated by Carleton, Norton, and Asmundson (2007) for increased efficiency in clinical and research settings. The scale has demonstrated strong psychometric properties and is a critical tool for assessing a transdiagnostic risk factor across various anxiety and mood disorders.

Keywords

Intolerance of Uncertainty, IUS, Worry, Generalized Anxiety Disorder, GAD, Anxiety, Cognitive vulnerability, Assessment scale, Psychological measurement, Self-report.

Authors

Kristin E. M. Buhr, Michel J. Dugas, R. Nicholas Carleton, Murray A. P. J. Norton, Gordon J. G. Asmundson

Purpose

The primary purpose of the Intolerance of Uncertainty Scale is to quantify individual differences in the characteristic negative reaction to ambiguity and the unknown. It specifically measures the extent to which a person perceives uncertain situations as stressful, unacceptable, or debilitating.

The scale serves as a diagnostic and research tool, particularly useful in cognitive-behavioral models of anxiety disorders, where Intolerance of Uncertainty is hypothesized to be a central cognitive vulnerability factor driving excessive worry and avoidance behaviors. The shorter IUS-12 version was developed to maintain the strong psychometric rigor of the original scale while reducing administration time, making it highly valuable for quick screening and repeated measures in clinical trials.

Construct

The IUS measures the psychological construct of Intolerance of Uncertainty (IU). This construct is defined not merely as a dislike of uncertainty, but as a dispositional negative reaction to uncertain events, characterized by a tendency to believe that uncertainty is fundamentally stressful, unfair, and reflects negatively on one’s competence.

IU is considered a transdiagnostic factor, meaning it is not specific to a single disorder but contributes significantly to the symptom severity and maintenance of multiple anxiety and mood disorders, including Generalized Anxiety Disorder (GAD), social anxiety, and depression. High scores on the IUS indicate a greater emotional, cognitive, and behavioral difficulty in coping with ambiguity, leading to excessive attempts to control, predict, or avoid uncertain outcomes.

Validity

The IUS, in both its 27-item and 12-item versions, has demonstrated strong construct and criterion validity across numerous studies. Research indicates that the scale exhibits high convergent validity with measures of worry, anxiety, and neuroticism. Importantly, studies by Buhr and Dugas (2006) established its discriminant validity, showing that the IUS accounts for unique variance in pathological worry even when controlling for general anxiety and depression measures, confirming its distinct role in the etiology of GAD.

Furthermore, the IUS-12 has shown robust validity in predicting symptoms of social anxiety (Carleton et al., 2010) and has been found to be significantly elevated across a range of anxiety disorders, including panic disorder and obsessive-compulsive disorder, supporting its status as a core transdiagnostic construct.

Reliability

The reliability of the Intolerance of Uncertainty Scale is consistently reported as excellent. The original IUS-27 and the shorter IUS-12 both demonstrate high internal consistency (typically measured by Cronbach’s alpha), often exceeding .90 in clinical and non-clinical samples.

Test-retest reliability has also been confirmed across various time intervals, indicating that the IUS measures a stable trait-like characteristic. These strong reliability indices support the consistent and accurate measurement of the IU construct across diverse populations and settings.

Factor Analysis

Initial factor analysis of the IUS-27 suggested a multi-factor structure, though it is often scored as a single, unitary measure of IU. However, the development of the IUS-12 led to a more clearly defined two-factor structure, which has been consistently supported through confirmatory factor analysis (CFA), including in studies of non-English samples (e.g., Helsen et al., 2013).

The two factors identified in the IUS-12 are:

• Prospective Anxiety (Items 1-7): Reflects the tendency to plan ahead, seek certainty, and experience distress related to future unknown events.
• Inhibitory Anxiety (Items 8-12): Reflects the tendency to be paralyzed or unable to function in the face of uncertainty, leading to avoidance or inaction.

Instrument

Test Type: Self-report questionnaire

Format: Likert scale response format

Language Available: English, French, Dutch (and numerous other translations)

Population Group: Clinical and non-clinical adult populations

Age Group: Adolescents and Adults (typically 18+)

Population Details: Primarily developed and validated on university students and clinical samples diagnosed with Generalized Anxiety Disorder.

Test Methodology: Respondents rate the extent to which each statement is characteristic of them using a 5-point scale (1 = not at all characteristic of me, 5 = entirely characteristic of me).

Keywords

IUS-27, IUS-12, Prospective Anxiety, Inhibitory Anxiety, Psychopathology, Measurement, Cognitive-Behavioral Therapy, Transdiagnostic factor.

Authors

Author ORCID Identifier: N/A (Not provided in source content)

Affiliation Email addresses: N/A (Not provided in source content)

Correspondence Address: N/A (Not provided in source content)

Permissions & Fee and Test Year

The Intolerance of Uncertainty Scale is frequently used in academic research without charge, though formal permission should be sought from the original authors (Buhr & Dugas) for commercial or extensive clinical application. The original IUS-27 was formalized around 2002, following the foundational work in Kristin Buhr’s 2001 Master’s thesis. The IUS-12 short form was developed and published in 2007.

The original PDF instruments can be downloaded here: http://www.collectionscanada.gc.ca/obj/s4/f2/dsk3/ftp04/MQ64017.pdf and here: https://biblio.ugent.be/publication/2959485/file/6776170.pdf

Reference’s

• Buhr, Kristin E. M. (2001). Examination of the Relationship between Intolerance of Uncertainty and Worry. Montreal, Quebec, Canada, Masters of Art Thesis.
• Buhr, K., & Dugas, M. J. (2002). The Intolerance of Uncertainty Scale: psychometric properties of the English version. Behaviour research and therapy, 40(8), 931–45.
• Buhr, K., & Dugas, M. J. (2006). Investigating the construct validity of intolerance of uncertainty and its unique relationship with worry. Journal of Anxiety Disorders, 20(2), 222–236.
• Carleton, R. N., Collimore, K. C., & Asmundson, G. J. G. (2010). ‘‘It’s not just the judgements —It’s that I don’t know’’: Intolerance of uncertainty as a predictor of social anxiety. Journal of Anxiety Disorders, 24, 189-195.
• Carleton, R. N., Gosselin, P., & Asmundson, G. J. G. (2010). The Intolerance of Uncertainty Index: Replication with an English sample. Psychological Assessment, 22(2), 396-406.
• Carleton, R. N., Mulvogue, M. K., Thibodeau, M. A., McCabe, R. E., Antony, M. M., & Asmundson, G. J. G. (2012). Increasingly certain about uncertainty: Intolerance of uncertainty across anxiety and depression. Journal of Anxiety Disorders, 26, 468-479.
• Carleton, R. N., Norton, M. A. P. J., & Asmundson, G. J. G. (2007). Fearing the unknown: A short version of the Intolerance of Uncertainty Scale. Journal of Anxiety Disorders, 21, 105-117.
• Helsen, Kim., Bussche, Eva Van den., Vlaeyen, Johan W.S. Goubert, Liesbet. (2013). Confirmatory factor analysis of the Dutch Intolerance of Uncertainty Scale: Comparison of the full and short version. J Behav Ther Exp Psychiatry;44(1):21-9.

Items of the Intolerance of Uncertainty (IUS)

IMPORTANT: The following scale items must be preserved in their original language and must not be changed in any way.

Intolerance of Uncertainty (IUS-27)

1. Uncertainty stops me from ha‎ving a firm opinion.
2. Being uncertain means that a person is disorganized.
3. Uncertainty makes life intolerable.
4. It’s unfair not ha‎ving any guarantees in life.
5. My mind can’t be relaxed if I don’t know what will happen tomorrow.
6. Uncertainty makes me uneasy‚ anxious‚ or stressed.
7. Unforeseen events upset me greatly.
8. It frustrates me not ha‎ving all the information I need.
9. Uncertainty keeps me from living a full life.
10. One should always look ahead so as to avoid surprises.
11. A small unforeseen event can spoil everything‚ even with the best of planning.
12. When it’s time to act‚ uncertainty paralyses me.
13. Being uncertain means that I am not first rate.
14. When I am uncertain‚ I can’t go forward.
15. When I am uncertain I can’t function very well.
16. Unlike me‚ others always seem to know where they are going in their lives.
17. Uncertainty makes me vulnerable‚ unhappy‚ or sad.
18. I always want to know what the future has in store for me.
19. I can’t stand being taken by surprise.
20. The smallest doubt can stop me from acting.
21. I should be able to organize everything in advance.
22. Being uncertain means that I lack confidence.
23. I think it’s unfair that other people seem sure about their future.
24. Uncertainty keeps me from sleeping soundly.
25. I must get away from all uncertain situations.
26. The ambiguities in life stress me.
27. I can’t stand being undecided about my future.

Intolerance of Uncertainty (IUS-12)

1. Unforeseen events upset me greatly.
2. It frustrates me not ha‎ving all the information I need.
3. One should always look ahead so as to avoid surprises.
4. A small unforeseen event can spoil everything‚ even with the best planning.
5. I always want to know what the future has in store for me.
6. I can’t stand being taken by surprise.
7. I should be able to organize everything in advance.
8. Uncertainty keeps me from living a full life.
9. When it’s time to act‚ uncertainty paralyses me.
10. When I am uncertain‚ I can’t function very well.
11. The smallest doubt can stop me from acting.
12. I must get away from all uncertain situations.