The intolerance of uncertainty construct in the context of anxiety disorders: Theoretical and practical perspectives

Abstract

Modern anxiety disorder models implicitly include intolerance of uncertainty (IU) as a critical component for the development and maintenance of these pervasive social and economic concerns. IU represents, at its core, fear of the unknown – a long-recognized, deep-seated fear identified in normative and pathological samples. Indeed, the intrinsic nature of IU can be argued as evolutionarily supported, a notion buttressed by initial biophysiological evidence from uncertainty-related research. Originally thought to be specific to generalized anxiety disorder, recent research has clearly demonstrated that IU is a broad transdiagnostic dispositional risk factor for the development and maintenance of clinically significant anxiety. The available evidence suggests that theorists, researchers and clinicians may benefit from explicitly incorporating IU into models, research designs, case conceptualizations and as a treatment target.

Full text

10.1586 /ERN.12.82 937
ISSN 1473-7175
© 2012 Expert Reviews Ltd
www.expert-reviews.com
Perspective
Increasing interest in the potential broad appli-
cability for intolerance of uncertainty (IU) in
understanding psychopathology has prompted a
recent surge in research. The present article was
constructed to contextualize IU relative to exist-
ing models of anxiety; provide a historical, bio-
logical and evolutionary context therein; define
and delineate IU; review current self-report
measures for IU; review the transdiagnostic
research on IU and discuss how IU functions in
a clinical context. Avenues for future research are
explored before being highlighted in the ‘Expert
commentary’ and the ‘Five-year view’ sections.
Anxiety & uncertainty
Anxiety disorders represent a pervasive social
and economic concern [1 ,2] warranting increased
attention from researchers and policy makers.
Key models of anxiety-related psychopathology
describe anxiety and fear as having three key
components [3]: physiological (i.e., autonomic
nervous system activation), cognitive (i.e.,
interpretation of the environmental and
physiological stimuli) and behavioral (i.e., the
selected response to the stimuli). Theorists have
also differentiated anx iety from fea r in an attempt
to facilitate explanations of the interactions
between experience and behavior [3 ,4]. Fear
has been described as a protective response to a
current, identifiable threat (e.g., being attacked),
typically accompanied by strong physiological
reactions (e.g., increased autonomic arousal) and
a fight or flight response [3]. Anxiety has been
described as physiologically similar to fear in that
there is increased autonomic arousal; however,
rather than occurring in response to a current,
identifiable threat, anxiety occurs in response to
a pending or potential threat that may or may
not occur (e.g., the possibility of being attacked,
somewhere, sometime). That said, with respect
to the experience of anxiety, it could be argued
that most threatening stimuli are consequentially
threatening, in that threatening stimuli (e.g.,
being attacked) are threatening as a function of
anticipated consequences (e.g., pain or injury)
and patterns of reinforcement, rather than being
inherently threatening [5] . The anxiety response
is then accompanied by proactive avoidance
behaviors, rather than the reactive fight-or-flight
response associated with fear.
A key cognitive distinction associated with
anxiety appears to be a “sense of uncontrollability
focused on the possibility of future threat, danger
or other potentially negative events” [4]. In other
R Nicholas Carleton
Department of Psychology, University
of Regina, 3737 Wascana Parkway,
Regina, SK S4S0A2, Canada
nick.carleton@uregina.ca
Modern anxiety disorder models implicitly include intolerance of uncertainty (IU) as a critical
component for the development and maintenance of these pervasive social and economic
concerns. IU represents, at its core, fear of the unknown – a long-recognized, deep-seated
fear identified in normative and pathological samples. Indeed, the intrinsic nature of IU can be
argued as evolutionarily supported, a notion buttressed by initial biophysiological evidence from
uncertainty-related research. Originally thought to be specific to generalized anxiety disorder,
recent research has clearly demonstrated that IU is a broad transdiagnostic dispositional risk factor
for the development and maintenance of clinically significant anxiety. The available evidence
suggests that theorists, researchers and clinicians may benefit from explicitly incorporating IU
into models, research designs, case conceptualizations and as a treatment target.
The intolerance of uncertainty
construct in the context of
anxiety disorders: theoretical
and practical perspectives
Expert Rev. Neurother. 12( 8), 937–9 47 (2012)
Keywor ds: anxiety • depression • intolerance of uncer tainty • tolerance of ambiguity • transdiagnostic
Expert Review of Neurotherapeutics
2012
12
8
937
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© 2012 Expert Reviews Ltd
10.1586/ERN.12.82
1473-7175
1744-8360
The intolerance of uncertainty construct
Carleton
Expert Rev. Neurother.
Perspective
THeMed ArTICLe y Anxiety disorders
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words, the cognitive components of anxiety require a potential
future threat coupled with the potential of insufficient agency
to avoid or overcome the threat-related potential consequences.
In this context, agency refers specifically to human agency as
described by Bandura [6] – an emergent reciprocal interactivity
between internal and external determinants – and is influenced
by efficacy beliefs, goal representations and anticipated outcomes.
The absence of certainty or agency related to the threat and the
associated potential consequences creates anxiety. By contrast,
certainty about the threat and the associated potential conse-
quences or agency necessarily results in either calm (e.g., no threat
and/or capacity to avoid or cope with the threat and the associ-
ated potential consequences) or fear (e.g., the potential threat or
potential associated consequences become realized). For example,
if being attacked and the associated potential consequences some-
how transitions from a possibility to an impossibility (i.e., all such
threats and/or the associated potential consequences are perma-
nently removed), there will be no anxiety about being attacked.
Similarly, if capacity to avoid or cope with the threat-related
potential consequences becomes certain (e.g., being attacked
will not result in any form of injury considered threatening by
the person being attacked), there will be no anxiety about being
attacked. Alternatively, if being attacked and the associated poten-
tial consequences transitions from a future possibility into a cur-
rent certainty (i.e., the attack begins), what may have been anxiety
will have become fear.
There are at least three practical considerations within the
aforementioned interpretation of Suárez and colleagues’ quote
[4] that further contextualize the experience of anxiety and uncer-
tainty. The first consideration is absence of agency (i.e., a sense
of uncontrollability), although the presence of agency has long
been established as limited at best [7–9]. That said, the absence
of agency is not necessarily inherently threatening. For example,
many people willfully seek to abdigate some or all agency at dif-
ferent times and under different circumstances (e.g., deity-driven
determinism; the popularity of disinhibitory substances). The sec-
ond consideration involves the inescapability of the potential for
future negative outcomes. Specifically, all persons will experience
limitations of agency and all persons are at risk of experiencing
future negative outcomes. These realities mean that all people will
experience uncertainty, placing them at risk for experiencing anxi-
ety; however, not all persons will experience clinically significant
anxiety (i.e., associated with distress or impairment), which is
a distinction of degree instead of a distinction of kind [1 0] . The
distinction appears based on individual differences in capacity
to tolerate the inevitable uncertainty associated with insufficient
agency and negative outcomes. The third consideration involves
events potentially perceived as threats that are unequivocally
certain but are also, as of yet, unrealized. Practically speaking,
there is only one such threat – death. All other future threats
and the associated potential consequences remain uncertain (i.e.,
anxiety provoking) until they are realized, which prompts fear
rather than anxiety. The full debate about these considerations
is beyond the scope of this paper. In the interim, based on the
definition from Suárez and colleagues [4] and the postulates of
other researchers [11,12], uncertainty appears to be an important,
if not necessary, component of anxiety.
Biological & evolutionary perspectives
The available evidence from large undergraduate [13 ,14] , com-
munity [15] and clinical populations [12 ,1 6–2 1] has indicated that
the ability to tolerate uncertainty is a ubiquitous dispositional
characteristic with a range of scores, substantial construct vari-
ability, a generally normal distribution and observable influences
on behavior [22 ,23] . Tolerating uncertainty as an individual differ-
ence variable is important in the experience of anxiety and readily
integrates into the automatic (i.e., preconscious or preattentive)
and strategic (i.e., elaborative) processing postulated in informa-
tion processing models of anxiety [10, 24]. Mathews and MacLeod
conducted what may have been the first review of attention-based
anxiety research and concluded that the earliest analyses of stimuli
may serve only to classify a stimulus as threatening or not [25,26] .
Since then, researchers have further supported the automatic clas-
sification of stimuli [27, 28] and a recent review has underscored the
system as important for the development and maintenance of
anxiety disorders [29] . At this automatic level, the ability to toler-
ate uncertainty may be reflected in a bias towards classification
of a novel stimulus as threatening, therein increasing autonomic
arousal and facilitating perceptions of anxiety at strategic process-
ing levels. Such speculation is supported by theory and evidence
that uncertainty itself is considered threatening [30–32] and can
exacerbate the perception of threat [33 ,34]. Indeed, people who are
intolerant of uncertainty are more likely to interpret all ambiguous
information as threatening [35], contributing to significant somatic
stress reactions (e.g., increased heart rate, blood pressure [3 6,37] ).
Recent research has also demonstrated a relationship between
inability to tolerate uncertainty and the startle response, indepen-
dently of worry, which underscores the importance of automatic
processing associated with uncertainty and threat [38] . During
the subsequent strategic processing, a more complex assessment
of the threat potential occurs that likely interacts with automatic
and strategic assessments of the coping capacity; however, an ina-
bility to tolerate uncertainty may impair problem-solving skills,
inhibiting action and increasing avoidance of uncertainty [39].
As stimuli become increasingly novel, the ability to tolerate
ambiguity or uncertainty becomes increasingly important to
explain the experience of anxiety. Novel situations (i.e., the
unknown) activating the autonomic nervous system would
have been evolutionarily supported so long as the system was
not hyperactive. From an evolutionary perspective, activation
of the autonomic nervous system while exploring a completely
novel environment would help protect against predation,
but activation caused by the presence of any novelty in an
otherwise familiar environment would have been incapacitating.
Furthermore, humans would be best served by balancing
tolerance and IU [4 0– 42], a balance best described by a continuum
for fearing the unknown. Indeed, Kroener and Dugas [43] have
provided compelling evidence supporting the ability to tolerate
uncertainty as not just an individual difference variable, but as
a dispositional characteristic; moreover, initial evidence suggests
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Perspective
the characteristics a continuous latent structure throughout the
population [18]. In modern society (arguably in most industrial
countries), tolerating uncertainty functions less as a critical
component for survival and more as a broad dispositional
risk factor for the development and maintenance of clinically
significant anxiety and depression [12 , 19–21 ,44] .
Defining IU
Specific references to tolerating uncertainty as a dispositional
characteristic are increasingly popular, but remain relatively
recent [11 ,12,18,20,4 3–47]. An early and potent reference to difficul-
ties tolerating uncertainty was made by Lovecraft in 1927, “The
oldest and strongest emotion of mankind is fear, and the oldest
and strongest kind of fear is fear of the unknown” (as cited in [48]).
The Lovecraft reference reflects the long-standing acceptance that
a fear of the unknown is a very basic human fear. Subsequently,
researchers have made references associated with uncertainty –
such as intolerance of ambiguity [49] – but specific references to
difficulty tolerating uncertainty did not appear until relatively
recently [50 ,51] . Uncertainty was described as a state resulting
from aversive or ambiguous stimuli, wherein increasing difficulty
tolerating uncertainty results in hypervigilance for threat cues.
Thereafter, difficulties managing uncertainty were empirically
associated with less-effective responses to negative life events
[52] and a desire for cognitive closure irrespective of the specifics
associated with that closure [53 ].
Researchers later postulated a causal relationship between
uncertainty and worry [31] , specified the related construct as
IU [32] , and provided the first construct-specific definition “as a
relatively broad construct representing cognitive, emotional, and
behavioral reactions to uncertainty in everyday life situations”
[32] . The definition was revised several times thereafter (Tabl e 1).
First, a focus on perception was added to the definition ([54] , as
cited in [55] ) and the construct broadened to include difficulties
with ambiguity and unpredictable changes ([5 6] , as cited in [57 ]).
Second, IU was described as a predisposition to react negatively
to uncertain events, independently of the perceived probabilities
and consequences associated therein [5 8]. Third, IU was described
as an excessive tendency to consider negative events as unaccep-
table; however, the probability of such events to occur are small
[59] . Fourth, IU was defined as a cognitive bias affecting the
perception, interpretation and behaviors associated with uncer-
tainty [60] . Fifth, IU was conceptualized as an excessive tendency
to find uncertainty distressing, to believe surprises are negative
and should be avoided, and to believe uncertainty about the
future is unfair [61, 62]. Sixth, the definition of IU was expanded
to include beliefs about the inability to cope with ambiguity
and change [47].
Reviews of the aforementioned research did not unanimously
support a single definition [55, 63], with some researchers argu-
ing there are “major conceptual problems with the construct of
IU” [63] . Since then, IU has been described as a future-oriented
dispositional characteristic resulting from negative beliefs about
uncertainty and its implications [45]. In the same year, a refined
definition of Dugas et al. was also proposed – specifically, that
IU is the tendency for an individual to consider the possibil-
ity of a negative event occurring as unacceptable and threaten-
ing, irrespective of the probability of its occurrence [11] . The
definition included the notion that IU was best represented by
prospective (e.g., cognitive) and inhibitory (e.g., behavioral)
dimensions that reflect a latent fear of the unknown [12 , 64] , a
duality that was further supported by the originator of the IU
construct, Freeston, and his colleagues [65]. Indeed, it appears
that IU definitions have all been elaborations on responses to
that “oldest and strongest kind of fear” (as cited in [48]), a fear of
the unknown. Conceptualizing IU as representing, at its core,
a dispositional fear of the unknown provides a clear and defen-
sible starting point for developing the construct in normative
and pathological samples. The suggested core definition is not
intended to invalidate previous definitions; instead, the previous
definitions can be reconceptualized as describing expressions
(typically clinical) of the core construct with variable intensity
along a continuum [18]. The proposed reconceptualization fits
well with recent recommendations that IU should be defined
continuously and specifically [65] , as well as initial evidence for
the continuous nature of IU [18]; however, the proposal warrants
theoretical and practical debate that will hopefully lead to a
consensus within the scientific community.
Uncertainty & ambiguity
A review of IU relative to (in)tolerance of ambiguity is important
because of the semantic overlap and differences in research tra-
jectories for the two constructs. A comprehensive history of the
differentiation is beyond the scope of the current paper, but is
available elsewhere [55]. In short, Frenkel-Brunswik posited toler-
ance and intolerance of ambiguity as representing a continuum
of individual difference variables [49]. Tolerance of ambiguity was
originally defined as the “tendency to perceive ambiguous situa-
tions as desirable”, whereas intolerance of ambiguity was defined
as “the tendency to perceive (i.e., interpret) ambiguous situations
as sources of threat” [66]. Ambiguity was related to rigidity [67],
authoritarian syndrome [49,66], and thought to pervasively influ-
ence human behavior [49,68]. Researchers have focused on toler-
ance of ambiguity [69,70], but there is a paucity of clinical research
[52,71–73]. (In)tolerance of ambiguity has always implicitly
or explicitly included IU [49,66,68], reflecting a shared fear of
the unknown (see, for example, the Measure of Ambiguity
Tolerance) [74–76].
Efforts to differentiate (in)tolerance of ambiguity and IU have
occurred relatively recently. Greco and Roger may have provided
the earliest direct conceptual distinction in that unambiguous
life events (e.g., whether or not a person is being attacked) still
involve uncertainty (e.g., the outcome of the attack remains
unknown) [36]. Grenier et al. further delineated the constructs,
starting with the initial overlapping definitions (i.e., ambiguity
as a source of threat) [50,51] and then detailing the divergence [55].
As part of their comprehensive review, a conceptual difference
between (in)tolerance of ambiguity and IU was provided;
specifically, (in)tolerance of ambiguity focuses on the ‘here and
now’ (i.e., situations characterized by ambiguous or equivocal
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Expert Rev. Neurother. 12(8), (2012)
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Perspective
features), whereas IU focuses on future events (i.e., situations
interpreted as threatening because of the potentially negative
consequences). That said, there is a notable lacking of empirical
research on the distinction, with some researchers calling the
distinction “questionable” [63].
(In)tolerance of ambiguity and IU are likely expressed by the
same neurological process biases at the automatic processing
level [25,26,29,72] ; however, conceptual differences likely occur
during elaborative processing [55] . At the strategic level, (in)
tolerance of ambiguity arguably describes a continuum of abil-
ity to cope with situations that have recognized but undefined
elements (i.e., stimuli), resulting in a limited number of poten-
tial outcomes. For example, a significant other provides the
ambiguous verbal stimuli, ‘we need to talk’. The actors in the
situation are all certain, as are the component definitions of the
stimuli, but the overall meaning of the stimuli is ambiguous,
and that ambiguity occurs in the present. Furthermore, uncer-
tainty remains inherent in the ambiguity (i.e., even in a limited
set of potential outcomes, the outcome itself – the consequences
– remains unknown, as do the associated details therein). The
consequences associated with the ambiguous stimuli exist in
the future as an infinitely perpetuating series of interdependent
responses that become increasingly difficult – eventually impos-
sible – to predict. The consequences are necessarily uncertain
(i.e., unknowable) in the present and remain uncertain even
after the ambiguity is resolved. Accordingly, (in)tolerance of
ambiguity and IU might be conceptualized as constructs that
overlap as a function of the same core fear of the unknown;
however, (in)tolerance of ambiguity may be subsumed by IU
in that it reflects increasingly temporally immediate and cir-
cumscribed perspectives on fearing the unknown, based on
the necessary narrowing of some possibilities into certainties
(i.e., events that have already happened) as a person moves
through time. By contrast, IU may reflect increasingly tempo-
rally distant perspectives on fearing the unknown, based on
the necessary widening of possibilities into the future. In any
case, such speculation awaits empirical evidence and further
theoretical debate.
Irrespective of decisions on the final definitions, IU has, to
date, received much more focus in clinical research than (in)
tolerance of ambiguity [55] . The available evidence suggests
modest associations between tolerance of ambiguity and psy-
chopathology [77,78] ; however, there is longstanding evidence
that uncertainty can be inherently threatening [30] , facilitating
anxiety and exacerbating the perception of threat [33,3 4], therein
potentiating an infinite series of catastrophic possibilities [7 9].
Based on the theoretical postulates herein, and in line with prior
recommendations [55], it appears clinical research and practice
should continue to focus on IU rather than (in)tolerance of
ambiguity.
Measuring IU
The first measure designed to assess IU was the 27-item IU scale
(IUS) [32] that used a 5-point Likert scale ranging from 1 (not
at all characteristic of me) to 5 (entirely characteristic of me).
The internal consistency and 5-week test–retest reliability were
both high, and there was moderate convergent validity with
measures of worry, anxiety and depression; however, the factor
structure was unstable [14, 32,60] . As such, the 12-item Intolerance
of Uncertainty Scale, Short Form (IUS-12) [64] was proposed.
The IUS-12 has a strong correlation with the original scale (rs =
0.94–0.96) [64,80] , and has been shown to have two factors with
identically high internal consistencies (i.e., α = 0.85) [64]. The
factor names originally made explict reference to anxiety, but
McEvoy and Mahoney provided a compelling argument that
resulted in the names being changed to prospective IU (seven
items; e.g., ‘I can’t stand being taken by surprise’; cognitive
or prospective) and inhibitory IU (five items; e.g., ‘When it’s
time to act, uncertainty paralyses me’; behavioral or currently
paralyzing). A recent comprehensive review article exploring
the factor structures and associated latent components has pro-
vided strong evidence of the robust nature of the IU construct
Table 1. Intolerance of uncertainty defined.
Historical definitions (paraphrased) Year Ref.
A broad construct representing cognitive, emotional and behavioral reactions to uncertainty in everyday situations 1994 [32]
Individual perceptions of information in uncertain situations that lead to a set of cognitive, emotional and behavioral
reactions, as well as difficulties with ambiguity and unpredictable changes
1995 [54 –57]
A predisposition to react negatively to uncertain events, independently of the perceived probabilities and consequences
associated with the events
2000 [58]
The excessive tendency of an individual to consider it unacceptable that a negative event may occur, however small the
probability of its occurrence
2001 [5 9]
A cognitive bias affecting the perception, interpretation and behaviors associated with uncertainty 2002 [60]
An excessive tendency to find uncertainty distressing, to believe surprises are negative and should be avoided, and to
believe uncertainty about the future is unfair
2004 [61,62]
A set of beliefs about the inability to cope with ambiguity and change 2006 [4 7]
A future-oriented dispositional characteristic resulting from negative beliefs about uncertainty and its implications 2007 [45]
The tendency for an individual to consider the possibility of a negative event occurring as unacceptable and threatening,
irrespective of the probability of its occurrence
2007 [11]
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as described [65]. Furthermore, evidence to date has indicated
differential discriminant validity associated with each subscale,
such that prospective IU appears more strongly associated with
generalized anxiety disorder (GAD) and obsessive compul-
sive disorder (OCD; i.e., anticipation of uncertainty), whereas
inhibitory IU appears more strongly associated with panic dis-
order, social anxiety disorder and depression (i.e., uncertainty
produces inhibition) [12, 19–2 1,44,81] . The IUS-12 has excellent
convergent validity with the original [11, 64,80] and the psycho-
metric properties have all been replicated and reified in clinical
and nonclinical samples [11 ,12,8 0]. The IUS-12 is particularly
useful for research because it is psychometrically comparable
to the longer IUS [80] , the Uncertainty Response Scale (which
is also much longer, but with a sound construction and good
potential) [36 ], and the new symptom-focused Intolerance of
Uncertainty Index (IUI) [82,8 3]. In addition, while the IUI
was developed largely as a clinical and outcome measure for
worry, the IUS-12 has been designed specifically to research
the core aspects of IU across different populations and differ-
ent disorders.
IU across anxiety disorders & depression
Researchers have historically focused on studying IU in GAD.
Indeed, as an independent construct IU was originally developed
as part of the explanation for the perpetual, often disabling worry
described as the hallmark of GAD [31,32]. Worry was identified as a
cognitive strategy used in attempts to control the unknown [58,84]
and the initial research supported the notion that, relative to people
with other anxiety disorders, people with a principle diagnosis of
GAD reported higher levels of IU [61,85]; however, the initial sample
sizes were relatively small and the tool used to measure IU was
designed to help identify and describe GAD. With that in mind,
IU as measured by the IUS is indeed a robust predictor of worry
[77,86]. People with high IU have been shown to worry more when
anxious than when calm [87], and some early research supported
notions that IU represented an individual difference variable that
distinguished GAD from other anxiety disorders [61,85,88]. Despite
the associations between IU, worry and GAD, neither IU nor
worry is exclusive to GAD [4,10,89] (see also [201]); moreover, other
forms of repetitive negative thinking (e.g., rumination, postevent
processing) are also not exclusive to GAD and instead appear to
represent transdiagnostic constructs [90–92] that warrant additional
research.
Initial suggestions that IU may be a construct applicable
beyond GAD stemmed from indirect comparisons by Norton,
who assessed relative contributions of IU across different ethnic
groups and diagnostic symptoms [14 ,8 8]. A subsequent investiga-
tion by Norton using a large undergraduate sample was able to
demonstrate the broad potential applicability of IU with struc-
tural equation modeling [93] . Contemporary evidence indicated
that IU was comparable in undergraduate persons likely meeting
criteria for OCD and/or GAD [47] , as well as clinical samples with
OCD [17] . The comparability was particularly strong for persons
with OCD and checking behaviors, and the results have since
been replicated [9 4,9 5].
Researchers working with large undergraduate samples have
also found evidence for an interdependent relationship between
IU, anxiety sensitivity – the fear of physical sensations associ-
ated with anxiety [96] – and panic disorder [11,87], such that IU
may be necessary for anxiety sensitivity [11]. Similarly, data from
undergraduate, community and clinical participants indicate the
relationship between IU and social anxiety appears comparable
to the relationship between the hallmark fear of negative evalu-
ation and social anxiety [81,95,97–100]. There has also been recent
evidence from similar samples of a relationship between IU and
health anxiety [101]. Furthermore, there is growing evidence from
undergraduate, community and clinical participant data that
IU is related to depression [19–21,93,95,98–10 0,102–10 4]; however, the
specific mechanisms underlying the relationship between IU and
depression warrant additional research [103–105]. For example, IU
may be related to depression as a function of the relationship
between IU and anxiety, and the relationship between anxiety
and depression. Rumination and worry about potentially nega-
tive consequences – neither of which is exclusive to GAD [90–92] –
can also be expected to increase as a function of IU, which would
then serve to increase depression symptoms. IU may also facili-
tate pessimistic certainty in that accepting negative consequences
as inevitable may be preferred to tolerating uncertainty.
A recent meta-analysis including 58 articles from the available
empirical research also found no support for the idea that IU
is GAD specific [106]; instead, the authors suggested previous
evidence that IU differentiates GAD from other disorders may
have been influenced by the GAD-specific content assessed by
the original IUS. That meta-analytic evidence was further sup-
ported by two studies using hierarchical regression analyses with
data from large samples of clinical patients (n = 463 and n =
218) with various anxiety disorders [12,21], wherein IU explained
variance in all symptom measures, even after controlling for
neuroticism [12]. IU has predicted variance in symptoms beyond
neuroticism [20,97], anxiety sensitivity [11,59,81,97], fear of anxi-
ety [87], metabeliefs [16,107] and positive and negative affectivity
[81]. Similarly, a large comparative analysis of IU – as measured
by the IUS-12 – was recently completed using Kernel density
estimation curves, analyses of variance, and a multiple-group
confirmatory factor analysis of invariance with data from clinical
(i.e., patients diagnosed with a variety of anxiety disorders or
depression; n = 376), community (n = 571) and undergradu-
ate samples (n = 428) [44]. The results indicated no differences
in IU endorsement between persons diagnosed with different
anxiety disorders or depression, but all such persons reported
significantly and substantially higher IU relative to commu-
nity and undergraduate samples. The aforementioned studies
have also evidenced different relationships between prospective
IU (i.e., the cognitively focused prospective dimension of IU),
inhibitory IU (i.e., the behaviorally focused dimension of IU)
and several symptom profiles. Specifically, the prospective IU
subscale has been more related to worry and obsessive compul-
sive symptoms, whereas the inhibitory IU subscale has been
more related to social anxiety, panic, agoraphobia and depres-
sion [12,19–21,44,95,108]. The inhibitory IU subscale also appears
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Expert Rev. Neurother. 12(8), (2012)
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to be specifically related to the startle response under threat
conditions [38].
Based on the available evidence, there appears to be overwhelm-
ing support for the notion that IU, certainly as described herein
and measured by the IUS-12, is not specific to GAD. Instead,
IU appears to represent a broad dispositional risk factor for the
development and maintenance of clinically significant anxiety
and depression. The next steps involve working to more formally
integrate IU into current theoretical models, while including
measures of IU in subsequent research. Clinicians should also
consider assessing IU with the IUS-12 as a dispositional risk factor
and as an outcome measure for patients with clinically significant
anxiety or depression.
Formal integration of IU into current theoretical models is
well beyond the scope of this article. In the interim, this review
should serve to provide insight and direction for theorists. As
for measurement of IU, there appears to be evidence for GAD-
specific elements within the original IUS [32,10 6]. Those elements
have proved useful for GAD research and clinical work; how-
ever, researchers and clinicians working in other areas should
consider using the now well-supported IUS-12 [12 , 64,80,100].
There are also other measures for researchers and clinicians to
consider. The 48-item Uncertainty Response Scale [36] and the
45-item Intolerance of Uncertainty Index [82,83] also warrant
additional exploration as more extensive measures of IU and
related symptoms. Researchers have also developed a modified
version of the IUS-12 that distinguishes between trait (IUS-12)
and state (IUS-SS) IU [20,21] . The IUS-SS has participants select
a primary concern, describe a related distressing situation, and
then complete items from the IUS-12, but with specific reference
to the described situation. This ingenious modification served
to further underscore the transdiagnostic nature of IU and the
potential research and clinical utility of the construct. Indeed,
the evidence to date suggests an important, possibly interactive
relationship between trait and state IU that warrants additional
research.
IU & clinical perspectives
From a clinical perspective, IU may be extremely beneficial as
a robust transdiagnostic construct. Longitudinal research on
IU and GAD has consistently demonstrated that changes in IU
predict changes in pathology [5 8, 87,10 9–111]; moreover, there is now
evidence that changes in IU are also associated with changes in
social anxiety symptoms [112 ,11 3]. These clinical results further
support a directional relationship wherein IU serves as a broad
predispositional vulnerability factor.
In many ways, all therapies can be described as attempts to
mitigate IU in one of five ways:
• Remove or minimize a catastrophic misperception of threat
resulting from uncertainty (i.e., absent information);
• Remove or minimize a realistic threat;
• Remove or minimize the uncertainty;
• Creating capacity to cope with what are perceived as cata-
strophic eventualities associated with uncertainty;
• Increasing the ability to tolerate uncertainty (i.e., treating the
uncertainty itself as a threat).
Correcting perceptions of exaggerated negative consequences
stemming from the presence of uncertainty surrounding a real or
perceived threat may well be sufficient, particularly if the exag-
gerated consequence was the primary area of concern. Removing
a realistic threat, where possible, would also certainly be suf-
ficient, at least in the short term; however, there are an infinite
number of potentially realistic threats, making removing all
threats impractical. Removing all uncertainty is also imprac-
tical, if not impossible. Creating capacity to cope is certainly
practical and well warranted; however, ensuring that capacity
generalizes from a necessarily few number of specific threats to
a more general sense of realistic agency to cope with the infi-
nite number of possible threats is a far more challenging task.
Therapies that work to remove threats, increase certainty, and
create coping capacity, all facilitate a sense of agency – illusory
or otherwise – thereby reducing clinically significant symptoms
of anxiety (and probably depression). Increasing tolerance for
uncertainty, while potentially more challenging, may well provide
the most pervasive benefits. Dugas and Ladouceur have already
developed, tested and detailed a treatment designed to reduce
IU [10 9] . Dugas and Ladouceur’s treatment for IU – or elements
therein (e.g., re-evaluation of worry beliefs; problem orientation
training, cognitive exposure) – may provide substantial addi-
tional benefit to persons with any form of clinically significant
anxiety or depression. From a slightly broader perspective, clini-
cians may benefit by being mindful of the IU implicit in anxiety
and the reality that they have only the aforementioned avenues
to interact with a patient’s fear of the unknown. As such, clini-
cal researchers should continue to explore the transdiagnostic
treatment potential of reducing IU.
Expert commentary
“The oldest and strongest emotion of mankind is fear, and the
oldest and strongest kind of fear is fear of the unknown” (as
cited in [48]); there is no doubt in my mind that IU, as defined
by a core fear of the unknown, represents a critical construct
for understanding anxiety disorders. Despite initial theory and
evidence of IU as specific to one or two anxiety disorders, there
is now overwhelming evidence that it represents a broad trans-
diagnostic dispositional risk factor for the development and main-
tenance of clinically significant anxiety. The nonspecific nature of
IU with respect to diagnoses does not mean the construct lacks
utility. Instead, the specific and narrow core of the IU construct
(i.e., fear of the unknown), coupled with its pervasive relevance
as seen in the expanding clinical definitions, affords theoreti-
cal and clinical opportunities for a variety of disorders in a way
that other constructs may not, particularly given new evidence
of trait and state expressions of IU. The perceived longstand-
ing relationship between IU and the human experience supports
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Perspective
substantial potential utility in making explicit the implicit fear
of the unknown in our models of anxiety. Furthermore, there
is growing evidence that IU also represents a dispositional risk
factor for depression – an intriguing possibility that warrants
substantially more investigation. I expect that the automatic and
strategic methods people use to cope with IU will eventually
help to explain not only the development and maintenance of
anxiety and depression, but also the relationships between the
three constructs.
Five-year view
International and transdiagnostic research exploring IU is now
increasing at an exciting rate. As researchers and clinicians come
to recognize the pervasive nature of IU, I expect we will see a
substantial increase in related research and thereafter explicit inte-
gration into models of psychopathology. We will see refinement
of measures and I expect a debate about the definition that may
eventually refine the construct to a core fear of the unknown with
several symptom expressions – possibly akin to the anxiety sensitiv-
ity construct and associated definitions [96]. I expect replications
of the more recent investigations of IU, further assessing whether
the transdiagnostic communalities found in the studies to date are
indeed robust. Accordingly, I also expect there will be explorations
of the transdiagnostic utility of Dugas and Ladouceur’s protocol
[109], using the entire IU-focused treatment or using elements of
the treatment as adjuvants.
I expect there will be researchers who will fill the empirical
gaps associated with the relationships postulated in this article
regarding IU, cognitive psychology, neuropsychology, biological
psychology and evolutionary psychology. In particular, I hope
to see empirical investigations of IU as it relates to automatic
and strategic processing, startle responses, as well as increasingly
elegant biological models for understanding IU. We will also
see a large increase in IU research with child, adolescent, and
geriatric populations. We will see investigations detailing the
impact of IU on readily apparent and replicable behaviors – not
only presumed relationships with complex behaviors, but also
demonstrated relationships with behaviors. Similarly, we will
see replications and extensions of key research exploring IU and
decision making [22,23]. I expect we will also see a great deal of
investigation and debate regarding the inhibitory (e.g., behav-
ioral) and prospective (e.g., cognitive) dimensions of IU and
the practical and theoretical utility of those distinctions. Across
both dimensions, the new research exploring the trait and state
expressions of IU will further inform our understanding of how
IU functions to facilitate the development and maintenance of
psychopathologies.
We will also see an exploration of IU in nonclinical contexts,
likely associated with explorations of IU and a variety of
personality traits. I expect we will see increased recognition of
the importance of IU, not just for mental health professionals,
but for all health professionals. For example, recognizing IU
as a broad vulnerability may help physicians and nurses to
reduce patient health anxiety – and the associated personal
and economic costs – by mitigating uncertainty in one of
the aforementioned ways. As such, I expect there will be
explorations of managing IU in a variety of contexts outside of
what we currently recognize as the domain of mental health.
We may even see IU explored in other domains where factors
influencing decision-making play a prominent role, such as
industrial/organization psychology. There is definitely no way
to know exactly what will happen next as the research on IU
proliferates, but in this case, the uncertainty is what makes
research so exciting.
Financial & competing interests disclosure
The author has no relevant affiliations or financial involvement with any
organization or entity with a financial interest in or financial conflict with
the subject matter or materials discussed in the manuscript. This includes
employment, consultancies, honoraria, stock ownership or options, expert
testimony, grants or patents received or pending, or royalties.
No writing assistance was utilized in the production of this manuscript.
Key issues
• Intolerance of uncertainty (IU) represents, at its core, fear of the unknown.
• IU and (in)tolerance of ambiguity are arguably distinct, with a key factor being relative distance in time; however, both share a core fear
of the unknown.
• There is an argument to be made from the evolutionary psychology perspective that some IU is advantageously adaptive.
• The evolutionary argument coupled with attentional bias research of automatic and strategic biases suggest IU may have a measurable
biological basis.
• Based on the current definition of anxiety, there may be a logically necessary dependency between anxiety and IU in most cases.
• The IUS-12 appears to be a more robust measure of IU as a construct with a core fear of the unknown, whereas the IUS appears to
have elements specific to generalized anxiety disorder.
• IU is not specific to one anxiety disorder; instead, it appears to be a transdiagnostic dispositional risk factor for clinically significant
anxiety and depression.
• Theoretical and clinical models of anxiety and depression may benefit from making explicit the nature of the relationships with IU.
• A variety of health professionals, mental health professionals and other professions would all likely benefit from understanding the
pervasive impact IU can have on mental health, health-related behaviors and decision making.
• There is already at least one treatment specifically designed to reduce IU; the elements of that treatment warrant transdiagnostic
exploration as an option for mitigating uncertainty.
The intolerance of uncertainty construct

Expert Rev. Neurother. 12(8), (2012)
944
Perspective
References
Papers of special note have been highlighted as:
•ofinterest
••ofconsider ableinterest
1 Kessler RC, Berglund P, Demler O, Jin R,
Merikangas KR, Walters EE. Lifetime
prevalence and age-of-onset distributions of
DSM-IV disorders in the National
Comorbidity Survey Replication. Arch.
Gen. Psychiatry 62(6), 593–602 (2005).
2 Kessler RC, Chiu WT, Demler O,
Merikangas KR, Walters EE. Prevalence,
severity, and comorbidity of 12-month
DSM-IV disorders in the National
Comorbidity Survey Replication. Arch.
Gen. Psychiatry 62(6), 617–627 (2005).
3 Barlow DH. Anxiety and Its Disorders.
Guilford Press, NY, USA (2002).
4 Suárez L, Bennett S, Goldstein C, Barlow
DH. Understanding anxiety disorders from
a ‘triple vulnerability’ framework. In:
Oxford Handbook of Anxiety and Related
Disorders. Antony MM, Stein MB (Eds).
Oxford University Press, NY, USA,
153 –172 (20 09) .
• Providestheinitialframeworkfor
integratingintoleranceofuncertainty,
withacorefearoftheunknownasa
necessarycomponentofanxiety.
5 Skinner BF. Science and Human Behavior.
Macmillan, Oxford, UK (1953).
6 Bandura A. Human agency in social
cognitive theory. Am. Psychol. 44(9),
1175 –1184 (198 9) .
•• Providesevidenceforcomparable
endorsementratesofintolerance
ofuncertaintyinadiagnostically
diversesample,aswellasratifyingthe
psychometricsofthe12-itemIntolerance
ofUncertaintyScale,ShortForm(IUS-12).
7 Searle JR. Freedom and Neurobiology:
Reflections on Free Will, Language, and
Political Power. Cambridge University
Press, NY, USA (2004).
8 Burger JM. Desire for control and the
illusion of control: the effects of familiarity
and sequence of outcomes. J. Res. Pers. 20,
66 –76 (1986).
9 Langer EJ. The illusion of control. J. Pers.
Soc. Psychol. 32, 311–328 (1975).
10 Clark DA, Beck AT. Cognitive Therapy of
Anxiety Disorders: Science and Practice.
Guilford Press, NY, USA (2010).
11 Carleton R N, Sharpe D, Asmundson GJ.
Anxiety sensitivity and intolerance of
uncertainty: requisites of the fundamental fears?
Behav. Res. Ther. 45(10), 2307–2316 (2007).
12 McEvoy PM, Mahoney AE. Achieving
certainty about the structure of intolerance
of uncertainty in a treatment-seeking
sample with anxiety and depression.
J. Anxiety Disord. 25(1), 112–122 (2011).
13 Berenbaum H, Bredemeier K, Thompson
RJ. Intolerance of uncertainty: Exploring
its dimensionality and associations with
need for cognitive closure,
psychopathology, and personality.
J. Anxiety Disord. 22(1), 117–125 (2008).
14 Norton PJ. A psychometric analysis of the
Intolerance of Uncertainty Scale among
four racial groups. J. Anxiety Disord. 19(6 ),
699–707 (2005).
15 Sexton KA, Dugas MJ. Defining distinct
negative beliefs about uncertainty:
validating the factor structure of the
Intolerance of Uncertainty Scale. Psychol.
Assess. 21(2), 176–186 (2009).
16 Dugas MJ, Savard P, Gaudet A et al. Can
the components of a cognitive model predict
the severity of generalized anxiety disorder?
Behav. Ther. 38(2), 169–178 (2007).
17 Tolin DF, Abramowitz JS, Brigidi BD,
Foa EB. Intolerance of uncertainty in
obsessive-compulsive disorder. J. Anxiety
Disord. 17(2), 233–242 (2003).
18 Carleton RN, Weeks JW, Howell AN,
Asmundson GJ, Antony MM, McCabe R E.
Assessing the latent structure of the
intolerance of uncertainty construct: an
initial taxometric analysis. J. Anxiety
Disord. 26(1), 150–157 (2012).
19 McEvoy PM, Mahoney A E. To be sure, to be
sure: intolerance of uncertainty mediates
symptoms of various anxiety disorders and
depression. Behav. Ther. 43(3), 533–545 (2012).
20 Mahoney AE, McEvoy PM. Trait versus
situation-specific intolerance of uncertainty
in a clinical sample with anxiety and
depressive disorders. Cogn. Behav. Ther.
41(1), 26 –39 (2012).
21 Mahoney AE, McEvoy PM. A
Transdiagnostic examination of intolerance
of uncertainty across anxiety and depressive
disorders. Cogn. Behav. Ther. doi:10.1080/1
6506073.2011.622130 (2011) (Epub ahead
of print).
22 Ladouceur R, Talbot F, Dugas MJ.
Behavioral expressions of intolerance of
uncertainty in worry. Experimental findings.
Behav. Modif. 21(3), 355–371 (1997).
23 Luhmann CC, Ishida K, Hajcak G.
Intolerance of uncertainty and decisions
about delayed, probabilistic rewards. Behav.
Ther. 42(3), 378–386 (2011).
24 Bar-Haim Y, Lamy D, Pergamin L,
Bakermans-Kranenburg MJ, van IJzendoorn
MH. Threat-related attentional bias in anxious
and nonanxious individuals: a meta-analytic
study. Psychol. Bull. 133(1), 1–24 (2007).
25 Mathews A, MacLeod C. Cognitive approaches
to emotion and emotional disorders. Annu.
Rev. Psychol. 45, 25–50 (1994).
26 Mathews A, MacLeod C. Cognitive
vulnerability to emotional disorders. Annu.
Rev. Clin. Psychol. 1, 167–195 (2005).
27 McNally RJ. Automaticity and the anxiety
disorders. Behav. Res. Ther. 33(7), 747–754
(1995).
28 Bradley BP, Mogg K, Millar N, White J.
Selective processing of negative information:
effects of clinical anxiety, concurrent
depression, and awareness. J. Abnorm.
Psychol. 104(3), 532–536 (1995).
29 Cisler JM, Koster EH. Mechanisms of
attentional biases towards threat in anxiety
disorders: An integrative review. Clin.
Psychol. Rev. 30(2), 203–216 (2010).
30 Epstein S. The nature of anxiety with
emphasis upon its relationship to
expectancy. In: Anxiety: Current Trends in
Theory and Research. Spielberger CD (Ed.).
Academic Press, NY, USA, 291–337
(1972).
31 Dugas MJ, Letarte H, Rhéaume J, Freeston
MH, Ladouceur R. Worry and problem
solving: evidence of a specific relationship.
Cog. Ther. Res. 19, 109–120 (1995) .
32 Freeston M, Rhéaume J, Letarte H, Dugas
MJ, Ladouceur R. Why do people worry?
Pers. Individ. Differ. 17, 791–802 (1994).
33 Dugas MJ, Hedayati M, Karavidas A, Buhr
K, Francis K, Phillips NA. Intolerance of
uncertainty and information processing:
evidence of biased recall and interpretations.
Cog. Ther. Res. 29(1), 57–70 (2005).
34 Hock M, Krohne HW. Coping with
threat and memory for ambiguous
information: testing the repressive
discontinuity hypothesis. Emotion 4(1),
65–86 (2004).
35 Heydayati M, Dugas MJ, Buhr K, Francis K.
The relationship between intolerance of
uncertainty and the interpretation of
ambiguous and unambiguous information.
Presented at: The Annual Convention of the
Association for Advancement of Behaviour
Therapy. Boston, MA, USA, November
2003.
36 Greco V, Roger D. Coping with uncertainty:
the construction and validation of a new
measure. Pers. Individ. Differ. 31, 519–534
(2001).
37 Greco V, Roger D. Uncertainty, stress and
health. Pers. Individ. Differ. 34, 1057–1068
(2003).
Carleton

945
www.expert-reviews.com
Perspective
38 Nelson BD, Shankman SA. Does intolerance
of uncertainty predict anticipatory startle
responses to uncertain threat? Int. J.
Psychophysiol. 81(2), 107–115 (2011).
39 Dugas MJ, Freeston MH, Ladouceur R.
Intolerance of uncertainty and problem
orientation in worry. Cog. Ther. Res. 21(6),
593–606 (1997).
40 Gigerenzer G. How to make cognitive
illusions disappear: Beyond ‘heuristics and
bi ases’. Eur. Rev. Soc. Psychol 2, 83–115
(1991).
•• Providesacomprehensivediscussionof
thedistinctionsbetweenintoleranceof
uncertaintyand(in)toleranceofambiguity,
andoffersdenitionsforeachconstruct.
41 Cosmides L. The logic of social exchange:
has natural selection shaped how humans
reason? Studies with the Wason selection
task. Cognition 31(3), 187–276 (1989).
42 Cosmides L, Tooby J. Are humans good
intuitive statisticians after all? Rethinking
some conclusions from the literature on
judgment under uncertainty. Cognition
58(1), 1–73 (1996).
43 Koerner N, Dugas MJ. An investigation of
appraisals in individuals vulnerable to excessive
worry: the role of intolerance of uncertainty.
Cog. Ther. Res. 32, 619–638 (2008).
44 Carleton RN, Mulvogue MK, Thibodeau
MA, McCabe RE, Antony MM,
Asmundson GJ. Increasingly certain about
uncertainty: intolerance of uncertainty
across anxiety and depression. J. Anxiety
Disord. 26(3), 468–479 (2012).
45 Dugas MJ, Robichaud M. Cognitive–
Behavioral Treatment for Generalized
Anxiety Disorder: from Science to Practice.
Routledge, NY, USA (2007).
46 Koerner N, Dugas MJ. A cognitive model
of generalized anxiety disorder: the role of
intolerance of uncertainty. In: Worry and its
Psychological Disorders: Theory, Assessment
and Treatment. Davey GC, Wells A (Eds).
Wiley, Chichester, UK (2006).
47 Holaway RM, Heimberg RG, Coles ME.
A comparison of intolerance of uncertainty
in analogue obsessive-compulsive disorder
and generalized anxiety disorder. J. Anxiety
Disord. 20(2), 158–174 (2006).
48 Joshi ST, Schultz DE. H. P. Lovecraft
Encyclopedia. Greenwood Press, CT, USA,
255 (2001).
49 Frenkel-Brunswik E. Intolerance of ambiguity
as an emotional and perceptual personality
variable. J. Pers. 18(1), 108–143 (1949).
50 Krohne HW. The concept of coping modes
– relating cognitive person variables to
actual coping behavior. Adv. Behav. Res.
Ther. 11(4), 235–248 (1989).
51 Krohne HW. Vigilance and cognitive
avoidance as concepts in coping research.
In: Attention and Avoidance. Krohne HW
(Ed.). Hogrefe & Huber, Toronto, ON,
Ca nad a, 19–50 (1993).
52 Andersen SM, Schwartz AH. Intolerance of
ambiguity and depression – a cognitive
vulnerability factor linked to hopelessness.
Soc. Cognition 10(3), 271–298 (1992).
53 Kruglansky AW. Motivations for judging
and knowing: implications for causal
attribution. In: The Handbook of
Motivation and Cognition: Foundation of
Social Behavior. Higgins ET, Sorrentino
RM (Eds). Guilford Press, NY, USA
333–368 (1990).
54 Ladouceur R, Dugas MJ, Freeston MH.
Intolerance of uncertainty in normal and
excessive worry. Presented at: The World
Congress of Behavioral and Cognitive
Therapies. Copenhagen, Denmark (1995).
55 Grenier S, Barrette A-M, Ladouceur R.
Intolerance of uncertainty and intolerance
of ambiguity: similarities and differences.
Pers. Individ. Differ. 39(3), 593–600
(2005).
56 Sookman D, Pinard G. The Cognitive
Schemata Scale: a multidimensional
measure of cognitive schemas in obsessive-
compulsive disorder. Presented at: The
World Congress of Behavioral and Cognitive
Therapies. Copenhagen, Denmark (1995).
57 Craig KJ, Chamberlin SR. The
neuropsychology of anxiety disorders. In:
Textbook of Anxiety Disorders. Stein DJ,
Hollander E, Rothbaum BO (Eds).
American Psychiatric Publishing, VA, USA,
87–102 (2009).
58 Ladouceur R, Gosselin P, Dugas MJ.
Experimental manipulation of intolerance
of uncertainty: a study of a theoretical
model of worry. Behav. Res. Ther. 38(9),
933–941 (2000).
59 Dugas MJ, Gosselin P, Landouceur R.
Intolerance of Uncertainty and Worry:
Investigating Specificity in a Nonclinical
Sample. Cog. Ther. Res. 25(5), 551–558
(2001).
60 Buhr K, Dugas MJ. The Intolerance of
Uncertainty Scale: psychometric properties
of the English version. Behav. Res. Ther.
40(8), 931–945 (2002).
61 Dugas MJ, Marchand A, Ladouceur R.
Further validation of a cognitive–
behavioral model of generalized anxiety
disorder: diagnostic and symptom
specificity. J. Anxiety Disord. 19(3),
329–343 (2005).
62 Dugas MJ, Schwartz A, Francis K.
Intolerance of uncertainty, worry, and
depression. Cog. Ther. Res. 28(6), 835–842
(2004).
63 Starcevic V, Berle D. Cognitive specificity
of anxiety disorders: a review of selected
key constructs. Depress. Anxiety 23(2),
51– 61 (2006) .
64 Carleton RN, Norton MA, Asmundson GJ.
Fearing the unknown: a short version of
the Intolerance of Uncertainty Scale.
J. Anxiety Disord. 21(1), 105–117 (2007).
65 Birrell J, Meares K, Wilkinson A, Freeston M.
Toward a definition of intolerance of
uncertainty: a review of factor analytical
studies of the Intolerance of Uncertainty Scale.
Clin. Psychol. Rev. 31(7), 1198–1208 (2011).
66 Budner S. Intolerance of ambiguity as a
personality variable. J. Pers. 30, 29–50 (1962).
67 Eysenck HJ. The science of personality:
nomothetic. Psychol. Rev. 61(5), 339–342
(1954).
68 Bochner S. Defining Intolerance of
Ambigu ity. Psychological Record 15(3),
393–400 (1965).
69 Furnham A, Ribchester T. Tolerance of
ambiguity: A review of the concept, its
measurement and applications. Curr.
Psychol. 14 (3), 179–199 (1995 ).
70 Johnson HL, Court KL, Roersma MH,
Kinnaman DT. Integration as integration:
Tolerance of ambiguity and the integrative
process at the undergraduate level.
J. Psychol. Theol. 23(4), 271–276 (1995).
71 Tsui J. Tolerance for ambiguity,
uncertainty audit qualifications and
bankers perceptions. Psychol. Rep. 72(3),
915–919 (1993).
72 Leyro TM, Zvolensky MJ, Bernstein A.
Distress tolerance and psychopathological
symptoms and disorders: a review of the
empirical literature among adults. Psychol.
Bull. 136(4), 576–600 (2010).
73 Myers JR, Hendersonking DH,
Hendersonking EI. Facing technological
risks: The importance of individual
differences. J. Res. Pers. 31(1), 1–20 (1997).
74 Macdonald AP. Revised scale for ambiguity
tolerance – reliability and validity. Psychol.
Rep. 26(3), 791–798 (1970).
75 Rydell ST, Rosen E. Measurement and
some correlates of need-cognition. Psychol.
Rep. 19(1), 139–165 (1966).
• Providesevidenceratifyingthe
psychometricsoftheIUS-12relativeto
the27-itemIUscale.
The intolerance of uncertainty construct

Expert Rev. Neurother. 12(8), (2012)
946
Perspective
76 Norton RW. Measurement of ambiguity
tolerance. J. Pers. Assess. 39(6), 607–619
(1975).
77 Buhr K, Dugas MJ. Investigating the
construct validity of intolerance of
uncertainty and its unique relationship
with worry. J. Anxiety Disord. 20(2),
222–236 (2006).
78 Hamilton V. Perceptual and personality
dynamics in reactions to ambiguity. Br. J.
Psychol. 48(3), 200–215 (1957).
79 Worry and its Psychological Disorders:
Theory, Assessment and Treatment. Davey
GCL, Wells A (Eds). Wiley, Chichester,
UK (2006).
80 Khawaja NG, Yu L, NH. A comparison of
the 27-item and 12-item intolerance of
uncertainty scales. Clin. Psychol. UK 14(3),
97–106 (2010).
81 Carleton RN, Collimore KC, Asmundson
GJ. ‘It’s not just the judgements – it’s that I
don’t know’: intolerance of uncertainty as a
predictor of social anxiety. J. Anxiety
Disord. 24(2), 189–195 (2010).
82 Carleton RN, Gosselin P, Asmundson GJ. The
intolerance of uncertainty index: replication
and extension with an English sample. Psychol.
Assess. 22(2), 396–406 (2010).
83 Gosselin P, Ladouceur R, Evers A,
Laverdière A, Routhier S, Tremblay-Picard
M. Evaluation of intolerance of
uncertainty: development and validation of
a new self-report measure. J. Anxiety
Disord. 22(8), 1427–1439 (2008).
84 Dugas MJ, Buhr K, Ladouceur R. The role
of intolerance of uncertainty in the etiology
and maintenance of generalized anxiety
disorder. In: Generalized Anxiety Disorder:
Advances in Research and Practice.
Heimberg RG, Turk CL, Mennin DS
(Eds). Guilford Press, NY, USA, 143–163
(2004).
85 Ladouceur R, Dugas MJ, Freeston MH
et al. Specificity of generalized anxiety
disorder symptoms and processes. Behav.
Ther. 30(2), 191–207 (1999).
86 Laugesen N, Dugas MJ, Bukowski WM.
Understanding adolescent worry: the
application of a cognitive model. J. Abnorm.
Child Psychol. 31(1), 55–64 (2003).
87 Buhr K, Dugas MJ. The role of fear of
anxiety and intolerance of uncertainty in
worry: an experimental manipulation.
Behav. Res. Ther. 47(3), 215–223 (2009).
88 Sexton K A, Norton PJ, Walker JR, Norton
GR. Hierarchical model of generalized and
specific vulnerabilities in anxiety. Cogn.
Behav. Ther. 32(2), 82–94 (2003).
89 American Psychiatric Association. Diagnostic
and Statistical Manual of Mental Disorders.
APA, Washington, DC, USA (2000).
90 Watkins E, Moulds M, Mackintosh B.
Comparisons between rumination and
worry in a non-clinical population. Behav.
Res. Ther. 43(12), 1577–1585 (2005).
91 Harvey AG, Watkins E, Mansell W, Shafran
R. Cognitive Behavioural Processes Across
Psychological Disorders: A Transdiagnostic
Approach to Research and Rreatment. Oxford
University Press, Oxford, UK (2004).
92 McEvoy PM, Mahoney AE, Moulds ML.
Are worry, rumination, and post-event
processing one and the same ? Development
of the repetitive thinking questionnaire.
J. Anxiety Disord. 24(5), 509–519 (2010).
93 Norton PJ, Mehta PD. Hierarchical model
of vulnerabilities for emotional disorders.
Cogn. Behav. Ther. 36(4), 240–254 (2007).
94 Lind C, Boschen MJ. Intolerance of
uncertainty mediates the relationship
between responsibility beliefs and
compulsive checking. J. Anxiety Disord.
23(8), 1047–1052 (2009).
95 Khawaja NG, Mcmahon J. The relationship of
meta-worry and intolerance of uncertainty with
pathological worry, anxiety, and depression.
Behav Change 28(4), 165–180 (2011).
96 Anxiety Sensitivity: Theory, Research, and
Treatment of the Fear of Anxiety. Taylor S
(Ed). Erlbaum, NJ, USA (1999).
97 Boelen PA, Reijntjes A. Intolerance of
uncertainty and social anxiety. J. Anxiety
Disord. 23(1), 130–135 (2009).
98 Norton PJ, Sexton K A, Walker JR, Norton
GR. Hierarchical model of vulnerabilities
for anxiety: replication and extension with
a clinical sample. Cogn. Behav. Ther. 34(1),
50–63 (2005).
•• Providessubstantialmeta-analyticevidence
forthetransdiagnosticnatureofintolerance
ofuncertainty.
99 van der Heiden C, Melchior K, Muris P,
Bouwmeester S, Bos AE, van der Molen
HT. A hierarchical model for the
relationships between general and specific
vulnerability factors and symptom levels of
generalized anxiety disorder. J. Anxiety
Disord. 24(2), 284–289 (2010).
100 Boelen PA, Vrinssen I, van Tulder F.
Intolerance of uncertainty in adolescents:
correlations with worry, social anxiety, and
depression. J. Nerv. Ment. Dis. 198 (3) ,
194–200 (2010).
101 Boelen PA, Carleton RN. Intolerance of
uncertainty, hypochondriacal concerns,
obsessive-compulsive symptoms, and worry.
J. Nerv. Ment. Dis. 200(3), 208–213 (2012).
102 Butzer B, Kuiper NA. Relationships between
the frequency of social comparisons and
self-concept clarity, intolerance of
uncertainty, anxiety, and depression. Pers.
Individ. Differ. 41(1), 167–176 (2006).
103 Miranda R, Fontes M, Marroquin B.
Cognitive content-specificity in future
expectancies: role of hopelessness and
intolerance of uncertainty in depression
and GAD symptoms. Behav. Res. Ther.
46(10), 1151–1159 (20 08) .
• Providesevidenceforacausalrelationship
betweenintoleranceofuncertaintyand
clinicallysignicantsymptomsofanxiety.
104 Yook K, Kim KH, Suh SY, Lee KS.
Intolerance of uncertainty, worry, and
rumination in major depressive disorder
and generalized anxiety disorder. J. Anxiety
Disord. 24(6), 623– 628 (2010).
• Providesevidenceforacausal
relationshipbetweenintoleranceof
uncertaintyandclinicallysignicant
symptomsofanxiety.
105 Miranda R, Mennin DS. Depression,
generalized anxiety disorder, and certainty
in pessimistic predictions about the future.
Cog. Ther. Res. 31(1), 71–82 (2007).
106 Gentes EL, Ruscio AM. A meta-analysis of
the relation of intolerance of uncertainty to
symptoms of generalized anxiety disorder,
major depressive disorder, and obsessive-
compulsive disorder. Clin. Psychol. Rev.
31(6), 923–933 (2011).
107 De Bruin GO, Rassin E, Muris P. The
prediction of worry in non-clinical individuals:
the role of intolerance of uncertainty,
meta-worry, and neuroticism. J. of Psychopathol.
and Behav. Assess. 29(2), 93–100 (2007).
108 Boelen P. Intolerance of uncertainty and
emotional distress following the death of a
loved one. Anxiety. Stress. Coping 23(4),
471–478 (2010).
109 Dugas MJ, Ladouceur R. Treatment of
GAD. Targeting intolerance of uncertainty
in two types of worry. Behav. Modif. 24(5),
635–657 (2000).
110 Ladouceur R, Dugas MJ, Freeston MH,
Léger E, Gagnon F, Thibodeau N. Efficacy
of a cognitive–behavioral treatment for
generalized anxiety disorder: evaluation in
a controlled clinical trial. J. Consult. Clin.
Psychol. 68(6), 957–964 (2000).
111 Dugas MJ, Laugesen N, Bukowski WM.
Intolerance of uncertainty, fear of anxiety,
and adolescent worry. J. Abnorm. Child
Psychol. doi:10.1007/s10802-012-9611-1
(2012)(Epub ahead of print).
112 Mahoney AE, McEvoy PM. Changes in
intolerance of uncertainty during cognitive
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www.expert-reviews.com
Perspective
behavior group therapy for social phobia.
J. Behav. Ther. Exp. Psychiatry 43(2),
849–854 (2012).
113 Hewitt SN, Egan S, Rees C. Preliminary
investigation of intolerance of uncertainty
treatment for anxiety disorders. Clin.
Psychol-Uk 13(2), 52–58 (2009).
•• Providesevidenceforcomparable
endorsementratesofintolerance
ofuncertaintyinadiagnostically
diversesample,aswellasratif yingthe
psychometricsoftheIUS-12.
Website
201 American Psychiatric Association.
Diagnostic and Statistical Manual of Mental
Disorders V development website.
www.dsm5.org/Pages/Default.aspx
(Accessed 14 April 2011)
The intolerance of uncertainty construct