Cognitive Behaviour Therapy, 2015 Vol. 44, No. 1, 74–84, http://dx.doi.org/10.1080/16506073.2014.964303

An Examination of Distress Intolerance in Undergraduate Students High in Symptoms of Generalized Anxiety Disorder Emma M. MacDonald, Elizabeth J. Pawluk, Naomi Koerner and Alasdair M. Goodwill Department of Psychology, Ryerson University, Toronto, Ontario, Canada Abstract. People with generalized anxiety disorder (GAD) engage in maladaptive coping strategies to reduce or avoid distress. Evidence suggests that uncertainty and negative emotions are triggers for distress in people with GAD; however, there may also be other triggers. Recent conceptualizations have highlighted six types of experiences that people report having difficulty withstanding: uncertainty, negative emotions, ambiguity, frustration, physical discomfort, and the perceived consequences of anxious arousal. The present study examined the extent to which individuals high in symptoms of GAD are intolerant of these distress triggers, compared to individuals high in depressive symptoms, and individuals who are low in GAD and depressive symptoms. Undergraduate students (N ¼ 217) completed self-report measures of GAD symptoms, depressive symptoms, and distress intolerance. Individuals high in GAD symptoms reported greater intolerance of all of the distress triggers compared to people low in symptoms of GAD and depression. Individuals high in GAD symptoms reported greater intolerance of physical discomfort compared to those high in depressive symptoms. Furthermore, intolerance of physical discomfort was the best unique correlate of GAD status, suggesting that it may be specific to GAD (versus depression). These findings support continued investigation of the transdiagnosticity and specificity of distress intolerance. Key words: distress intolerance; generalized anxiety disorder; depression; psychopathology. Received 5 April 2014; Accepted 4 September 2014 Correspondence address: Naomi Koerner, PhD, Department of Psychology, Ryerson University, 350 Victoria Street, Toronto, ON M5B 2K3, Canada. Tel: 416-979-5000. Fax: 416-979-5273. Email: [email protected]

Introduction According to the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5; American Psychiatric Association [APA], 2013), generalized anxiety disorder (GAD) is a chronic disorder characterized by excessive worry and anxiety, and associated symptoms including muscle tension and feeling “keyed up.” Research suggests that people with GAD engage in maladaptive coping strategies, including worry, to reduce or avoid experiencing distress (Dugas, Gagnon, Ladouceur, & Freeston, 1998; Mennin, Heimberg, Turk, & Fresco, 2005); however, the types of experiences that people with GAD find distressing and difficult to withstand remain unclear. Thus, the present study sought to delineate the types of experiences that people with GAD q 2014 Swedish Association for Behaviour Therapy

have difficulty withstanding as this may provide information about factors related to their poor coping.

Distress triggers Leyro, Zvolensky, and Bernstein (2010) proposed that distress occurs when people are confronted with the following aversive triggers: uncertainty, negative emotions, ambiguity, frustration, or physical discomfort. Zvolensky, Vujanovic, Bernstein, and Leyro (2010) proposed a transdiagnostic model in which the five aforementioned distress triggers are lowerorder factors of a global distress intolerance factor. Empirical research confirmed that the five dimensions are distinct, but fit together within a single distress intolerance domain (Bardeen, Fergus, & Orcutt, 2013).

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Intolerance of uncertainty (IU) and intolerance of the experience of negative emotions have been studied extensively in GAD. IU is a dispositional characteristic that reflects longstanding negative beliefs about uncertainty. Although IU is now conceptualized as a transdiagnostic process (Mahoney & McEvoy, 2012), most of the research has been in worry and GAD (Dugas et al., 1998; Sexton & Dugas, 2009). The ability to withstand uncertainty is believed to influence people’s level of worry and distress in response to uncertain situations (Dugas, Schwartz, & Francis, 2004). When experiencing uncertainty, people with high IU report increased worry and information-seeking behaviours to reduce uncertainty (Rosen & Kna¨uper, 2009). Moreover, IU is a significant predictor of worry when controlling for depression and anxiety (Dugas, Freeston, & Ladouceur, 1997). Modifying IU directly influences symptoms of GAD, including reducing worry and anxiety (Dugas et al., 2003; Ladouceur et al., 2000). Research suggests that people with GAD may also have difficulty withstanding negative emotions. Mennin et al. (2005) proposed the emotion dysregulation theory of GAD, which suggests that people with GAD have negative attitudes about the experience of emotions due to the perception of heightened intensity and greater difficulty in regulating emotions (Mennin et al., 2005). Compared to people without GAD, those with GAD are more likely to engage in maladaptive behaviours, including avoidance, reassurance-seeking, and rash decision-making to manage distress from negative emotions (Fresco, Mennin, Heimberg, & Ritter, 2013; Pawluk & Koerner, 2013). In addition, intolerance of negative emotions predicts worry after controlling for depression and anxiety (Keough, Riccardi, Timpano, Mitchell, & Schmidt, 2010), suggesting that the experience and intolerance of negative emotions may be particularly relevant to people with GAD. Taken together, uncertainty and negative emotions evoke distress in people with GAD. Individuals with GAD may also have difficulty withstanding distress from the other triggers in Zvolensky et al.’s (2010) model, including ambiguity, frustration, or physical discomfort; however, only a few studies have examined whether these are triggers of distress in people with GAD. Moreover, the extent to which the distress

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associated with these triggers is elevated in people with GAD compared to people without GAD or those with a different disorder remains unknown. As for ambiguity, Buhr and Dugas (2006) reported that difficulty in tolerating ambiguity was associated with high worry. Although intolerance of ambiguity and IU may appear to be conceptually similar, they are several key differences. For example ambiguity is presentoriented; therefore, an equivocal situation that is in “here and now” is the source of distress. Alternatively, uncertainty is future-oriented; that is, not knowing what is going to occur in the future is the source of discomfort (see Grenier, Barrette, & Ladouceur, 2005, for a conceptual review). After controlling for IU, however, Buhr and Dugas (2006) found that the correlation between intolerance of ambiguity and worry was no longer significant. Thus, IU may be more closely related to worry than intolerance of ambiguity. Furthermore, intolerance of ambiguity and IU were only moderately correlated (r ¼ 0.42; Buhr & Dugas, 2006), which suggests non-redundancy. Therefore, despite the conceptual similarities, intolerance of ambiguity and IU are considered to be distinct constructs, and it is possible that ambiguity may be a trigger of distress in people with GAD. The experience of frustration can also be difficult to withstand. Frustration intolerance is characterized by a belief that life should be “easy, comfortable, and free of hassle” (Harrington, 2005). Frustration is experienced when this belief is violated (Harrington, 2005). Although no known research has examined whether people with GAD report difficulties tolerating frustration, higher anxiety is associated with greater frustration intolerance (Harrington, 2006). Therefore, it is possible that frustration may be distressing for individuals with GAD. Intolerance of physical discomfort is the last facet in Zvolensky et al.’s (2010) distress intolerance model. Although difficulty in tolerating physical discomfort, including painful and uncomfortable somatic experiences, is associated with anxiety (Schmidt, Richey, & Fitzpatrick, 2006), there is no published research investigating the degree to which people with GAD perceive physical discomfort as intolerable. However, the extant literature suggests that this question deserves

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further investigation. For example, some individuals with GAD report relaxationinduced anxiety due to the somatic changes that accompany the transition to a relaxed state, such as muscle tics (Heide & Borkovec, 1984). Individuals with GAD also report headaches and gastrointestinal distress (e.g., Lee et al., 2009; Mercante, Peres, & Bernik, 2011). Given that physical discomfort is part of the clinical profile of GAD, examination of beliefs about the ability to tolerate physical discomfort in people with GAD is warranted. In addition to the five aforementioned triggers of distress, researchers have postulated that anxiety sensitivity (AS) may be related to distress intolerance (Keough et al., 2010; Mitchell, Riccardi, Keough, Timpano, & Schmidt, 2013). Individuals high in AS report distress when experiencing changes in physical sensations (e.g., racing heart, dizziness) due to the fear of the negative consequences of these sensations (Reiss & McNally, 1985). Individuals with GAD consistently report elevated AS compared to non-clinical samples (Carleton, Abrams, Asmundson, Antony, & McCabe, 2009) and people with other anxiety disorders, except panic disorder (Naragon-Gainey, 2010). Although AS appears to be conceptually similar to intolerance of physical discomfort, empirical evidence indicates that the two constructs are weakly, and at best moderately, correlated (Mitchell et al., 2013; Schmidt et al., 2006). Mitchell et al. (2013) examined the factor structure of AS, intolerance of negative emotions, and intolerance of physical discomfort in non-clinical and clinical samples. A two-factor solution emerged in both samples: intolerance of physical discomfort loaded onto a physical intolerance factor and intolerance of negative emotions loaded onto an affective intolerance factor, with AS as a lower-order factor of intolerance of negative emotions. Because anxiety is typically experienced as a negative emotion, Mitchell et al. suggest that AS may be a facet of intolerance of negative emotions. AS was included in the present study as a distress trigger because AS is elevated in GAD and is related to, yet distinct from, intolerance of negative emotions and intolerance of physical discomfort.

Present study The present study examined the extent to which individuals high in GAD symptoms are

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intolerant of the six types of distress triggers: uncertainty, negative emotions, ambiguity, frustration, physical discomfort, and AS (Leyro et al., 2010; Mitchell et al., 2013), a question that has yet to be addressed. Given the novelty of the research question, analogue samples were used. There is convincing empirical (Vredenburg, Flett, & Krames, 1993) and conceptual (Abramowitz et al., 2014) support for the analogue approach to answering questions of clinical relevance. Individuals high in GAD symptoms were compared to (1) individuals high in depressive symptoms and (2) individuals low in GAD and depressive symptoms on measures of distress intolerance. Participants high in GAD and in depressive symptoms were excluded from analysis, as examination of the impact of comorbidity on distress intolerance was not an a-priori goal of the study. Depression was chosen as the comparison group to determine whether there are different sources of distress in these phenotypically similar disorders, especially given that some researchers have proposed that GAD and depression ought to be classified together as “distress disorders” (Watson, 2005). Both disorders involve pervasive distress and negative affect, and have overlapping symptoms (e.g., concentration difficulties, fatigue; APA, 2013), cognitions (perseverative thought; Hong, 2007), and behaviours (avoidance; Borkovec, Alcaine, & Behar, 2004; Ferster, 1973). Some distinguishing features include elevated muscle tension (Joormann & Sto¨ber, 1999) and normal levels of positive affect (Mennin, Holaway, Fresco, Moore, & Heimberg, 2007) in people with GAD compared to people with depression. In addition, many of the distress triggers described earlier have been examined in people with depression. For example, depression is correlated with greater difficulty in tolerating negative emotions (Mennin et al., 2007) and higher levels of AS compared to non-clinical samples (Peterson & Reiss, 1992; Taylor, Koch, Woody, & McLean, 1996). Alternately, people with elevated symptoms of depression do not report difficulty in tolerating ambiguity (Anderson & Schwartz, 1992) or physical discomfort (Schmidt et al., 2006) compared to people with low symptoms of depression. There is mixed evidence for the association between depression and frustration tolerance.

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Greater frustration intolerance is associated with elevated depression symptoms in undergraduate students (Stankovic´ &Vukosavljevic´Gvozden, 2011) and individuals with mixed psychopathology (Harrington, 2006), although other researchers have reported no correlation (Jibeen, 2013). Finally, Carleton et al. (2012) found that individuals with depression report equivalent levels of IU compared to people with GAD. Given that distress intolerance is theorized to be transdiagnostic, it was hypothesized that relative to individuals low in GAD and depression symptoms, those high in GAD symptoms or depressive symptoms would report significantly greater difficulty withstanding distress from all triggers. Comparing the two clinical groups, it was hypothesized that people with elevated symptoms of GAD would report greater difficulty withstanding ambiguity and uncomfortable physical sensations compared to people with elevated depression symptoms, but would not differ on the other distress triggers. No known studies have compared people with GAD and people with depression on measures of distress from ambiguity or physical sensations. However, given that people with GAD report greater difficulty in tolerating ambiguity and distress from physical sensations compared to people without GAD, whereas people with depression do not differ from people with low depressive symptoms, it was expected that people with GAD and people with depression would differ on these facets of distress intolerance. Finally, it was hypothesized that the distress intolerance dimensions would collectively distinguish participants high in GAD symptoms from those high in depressive symptoms and those low in GAD and depression. Given the mixed findings, no specific a-priori hypotheses were advanced about the unique contribution of each distress intolerance dimension to the prediction of GAD.

Method Participants The sample consisted of 217 undergraduate students (183 women, 34 men; mean age ¼ 21.13 years, SD ¼ 5.91) enrolled in an introductory psychology course who participated in the study for course credit. Selfreported ethnicities were as follows: Caucasian

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(44.4%), Asian-American/Asian Origin/Pacific Islander (27.1%), African American/Black/ Caribbean (6.5%), Middle Eastern (5.1%), Bi-Racial/Multi-Racial (4.7%), Latino-a/Hispanic (2.8%), American Indian/Alaska Native/ Aboriginal Canadian (0.5%), and “Other” (8.9%). Three participants did not report their ethnicity.

Measures and procedure All participants provided written informed consent before completing the measures. Following completion of the measures, participants were verbally debriefed. Generalized Anxiety Disorder QuestionnaireIV. The Generalized Anxiety Disorder Questionnaire-IV (GAD-Q-IV; Newman et al., 2002) is a self-report measure of Diagnostic and Statistical Manual of Mental Disorders-IV (DSM-IV; APA, 2000) GAD symptoms. The total score on the GAD-Q-IV ranges from 0 to 13; scores equal to or greater than 5.7 are suggestive of a diagnosis of GAD. The cut score represents an optimal balance between specificity (89%) and sensitivity (83%) and correctly classifies 88% of participants with GAD (Newman et al., 2002). Given that the core diagnostic criteria assessed by the GAD-Q-IV have not changed in DSM-5, the GAD-Q-IV remains a valid assessment instrument. The internal consistency of the GAD-Q-IV in the present study was a ¼ 0.80. Center for Epidemiologic Studies Depression Scale. The Center for Epidemiologic Studies Depression Scale (CES-D; Radloff, 1977) is a 20-item self-report measure of the frequency of depressive symptoms during the past week. Scores range from 0 to 60, with higher scores indicating greater depression severity. The present study used the conservative cut score of 27, which is indicative of the level of severity of symptoms associated with major depressive disorder (Zich, Attkisson, & Greenfield, 1990). The internal consistency of the CES-D in the present study was a ¼ 0.83.

Measures of Distress Intolerance The five measures of distress intolerance were recommended by Leyro et al. (2010). An AS measure was also included in the study. Intolerance of Uncertainty Scale. The Intolerance of Uncertainty Scale (IUS; Freeston, Rhe´aume, Letarte, Dugas, & Ladouceur, 1994; English translation, Buhr & Dugas, 2002) is a

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27-item self-report measure that assesses negative beliefs about uncertainty and its perceived consequences. The IUS total score has excellent internal consistency (a ¼ 0.94) and good convergent, criterion, and discriminant validity (Buhr & Dugas, 2002, 2006), as well as good stability over 5 weeks (r ¼ 0.74; Buhr & Dugas, 2002). A higher score on the IUS is indicative of greater IU. The internal consistency of the IUS in the present study was a ¼ 0.93. Distress Tolerance Scale. The Distress Tolerance Scale (DTS; Simons & Gaher, 2005) is a self-report measure that assesses the perceived inability to tolerate distress from negative emotions. The DTS has good internal consistency (a ¼ 0.82) and good test-retest reliability (r ¼ 0.63; Simons & Gaher, 2005). A lower score on the DTS is indicative of greater intolerance of negative emotions. The internal consistency of the DTS in the present study was a ¼ 0.89. Measure of Ambiguity Tolerance. The Measure of Ambiguity Tolerance (MAT-50; Norton, 1975) is a 61-item self-report measure that assesses people’s tolerance for ambiguity in a variety of domains (e.g., public image, problem-solving). The MAT-50 has good internal consistency (a ¼ 0.88) and good test-retest reliability (r ¼ 0.86; Norton, 1975). A lower score on the MAT-50 is indicative of a greater intolerance of ambiguity. The internal consistency of the MAT-50 in the present study was a ¼ 0.87. Frustration Discomfort Scale. The Frustration Discomfort Scale (FDS; Harrington, 2005) is a 28-item self-report measure that has four subscales: (1) Discomfort Intolerance, (2) Entitlement, (3) Emotional Intolerance, and (4) Achievement/Frustration. Leyro et al. (2010) suggested that only the Emotional Intolerance and Discomfort Intolerance subscales are relevant to distress intolerance. The present study excluded the Emotional Intolerance subscale from analyses because of the conceptual overlap with and strong correlation to the DTS (r ¼ 2 0.57, p , 0.001). Therefore, the Discomfort Intolerance subscale was the sole assessment of frustration intolerance in the present study. The Discomfort Intolerance subscale assesses expectations that life should be “easy, comfortable, and hassle-free” (Harrington, 2005). A higher score on the FDS is indicative of a greater intolerance of frustration. The internal con-

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sistency of the FDS Discomfort Intolerance subscale was a ¼ 0.88 in the present study. Discomfort Intolerance Scale. The Discomfort Intolerance Scale (DIS; Schmidt et al., 2006) is a five-item self-report measure that assesses perceived inability to tolerate uncomfortable physical sensations. The DIS has been shown to have good test-retest reliability over 12 weeks (Factor 1: r ¼ 0.63; Factor 2: r ¼ 0.66) and good internal consistency (a ¼ 0.70; Schmidt et al., 2006). A higher score on DIS is indicative of greater intolerance of physical distress. The internal consistency of the DIS was a ¼ 0.60 in the present study. Anxiety Sensitivity Index. The Anxiety Sensitivity Index (ASI; Reiss, Peterson, Gursky, & McNally, 1986) is a 16-item selfreport measure of fear of anxious arousal due to the belief that arousal has detrimental physical, cognitive, and social consequences. The ASI shows good internal consistency (a ¼ 0.82; Telch, Shermis, & Lucas, 1989). A higher score on the ASI is indicative of greater fear of the negative consequences of anxious arousal. In the present study, the internal consistency of the ASI was a ¼ 0.87.

Results The data were screened for outliers (z-scores beyond absolute values of 3.29; Tabachnick & Fidell, 2007). Two outliers were identified and were replaced by the next most extreme value in that measure’s distribution. Participants (N ¼ 217) were categorized into one of three groups using validated cut scores (Newman et al., 2002; Zich et al., 1990): (1) GAD, (2) depression, or (3) low GAD/low depression. The GAD group included participants who scored equal to or greater than 5.7 on the GAD-Q-IV and less than 27 on the CES-D (n ¼ 54). The depression group included participants who scored greater than or equal to 27 on the CES-D and less than 5.7 on the GAD-Q-IV (n ¼ 22). The low GAD/low depression group included participants who scored less than 5.7 on the GAD-Q-IV and less than 27 on the CES-D (n ¼ 141). Forty-five participants scored above the cut scores on the GAD-Q-IV and the CES-D and were excluded from analyses. The GAD, depression, and low GAD/low depression groups did not differ in mean age (F (2, 214) ¼ 4.83, p ¼ 0.87), gender

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distribution (x 2 (2) ¼ 0.21, p ¼ 0.90), or selfreported ethnicity (x 2 (14) ¼ 17.79, p ¼ 0.22).

Between-group differences in distress intolerance Point-biserial correlations were conducted between the categorical clinical status variables (i.e., GAD or no GAD/no depression; depression or no GAD/no depression) and the distress tolerance variables (i.e., IUS, DTS, MAT-50, FDS, DIS, and ASI) (see Table 1). Univariate analyses of variance revealed a significant main effect of group for all distress intolerance measures (see Table 2). Post-hoc analyses with Bonferroni adjustment (a/ number of comparisons) were conducted to follow up on significant main effects. Relative to the low GAD/low depression participants, people with elevated symptoms of GAD produced significantly higher scores on the ASI ( p , 0.05; d ¼ 0.67), DIS ( p , 0.05; d ¼ 0.62), IUS ( p , 0.001, d ¼ 0.61), and FDS ( p , 0.05, d ¼ 0.42), and significantly lower scores on the DTS ( p , 0.05, d ¼ 0.56) and the MAT-50 ( p , 0.05, d ¼ 0.40), which indicates higher intolerance of negative emotions and of ambiguity, respectively. When comparing the GAD group and the depression group, the GAD group produced significantly higher scores on the DIS ( p , 0.05, d ¼ 0.66). There were no significant differences between the GAD and depression groups on the other distress intolerance measures. Finally, compared to the low GAD/low depression group, the depression group pro-

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duced significantly higher scores on the ASI ( p , 0.05, d ¼ 0.84) and FDS ( p , 0.05, d ¼ 0.80), and significantly lower scores on the DTS (indicating higher intolerance of negative emotions; p , 0.05, d ¼ 0.86). There were no differences between the depression and low GAD/low depression group on the DIS, IUS, or MAT-50.

Prediction of group membership Two logistic regression analyses were conducted to test whether distress intolerance predicted (1) GAD versus low GAD/low depression and (2) GAD versus depression, and to determine which variables contribute the most to the differentiation. The first analysis examined the prediction of GAD versus low GAD/low depression. The regression model was significant, x 2 (6) ¼ 29.77, p , 0.001, and classified 73.3% of participants correctly. DIS was the only unique predictor of the presence of GAD (B ¼ 0.11, Wald x 2 (1) ¼ 5.52, p , 0.05, OR ¼ 1.12). A similar pattern emerged in the second analysis that examined the prediction of GAD versus depression. The model was also significant, x 2 (6) ¼ 17.08, p , 0.01, and classified 78.9% of cases correctly. DIS was again the only unique predictor of GAD presence (B ¼ 0.24, Wald x 2 (1) ¼ 7.93, p , 0.05, OR ¼ 1.27).

Discussion Summary of findings The present study examined the extent to which people with elevated symptoms of GAD differ

Table 1. Correlations between all symptom measures and distress tolerance variables

a

GAD Depressiona IUSb DTSb MAT-50b DISb FDSb ASIb

IUS

DTS

MAT-50

DIS

FDS

ASI

0.23** 0.08 – 2 0.55** 2 0.29** 0.15* 0.37** 0.46**

2 0.19** 2 0.19** 2 0.55** – 0.28** 2 0.14* 2 0.49** 2 0.43**

2 0.17* 0.02 2 0.29** 0.28** – 2 0.16* 2 0.24** 2 0.35**

0.24** 2 0.08 0.15* 2 0.14* 2 0.16* – 0.19** 0.18**

0.15* 0.16* 0.37** 2 0.49** 2 0.24** 0.19** – 0.41**

0.23** 0.17* 0.46** 2 0.43** 2 0.35** 0.18** 0.41** –

Note. IUS ¼ Intolerance of Uncertainty Scale; DTS ¼ Distress Tolerance Scale; MAT-50 ¼ Measure of Ambiguity Tolerance; DIS ¼ Discomfort Intolerance Scale; FDS ¼ Frustration Discomfort Scale Discomfort Intolerance; ASI ¼ Anxiety Sensitivity Index. *p , 0.05. **p , 0.01. a Point-Biserial correlations. 0 ¼ did not endorse symptoms of the disorder, 1 ¼ endorsed heightened symptoms of the disorder. b Pearson correlations.

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Table 2. Comparison of GAD, depression, and low GAD/low depression participants on the measures of distress intolerance

GAD n ¼ 54

Depression n ¼ 22

Low GAD/low depression n ¼ 141

Measure

M

SD

M

SD

M

SD

Fc

h2

IUS DTSd MAT-50d DIS FDS ASI

70.94a 44.35a 201.80a 17.33a 14.28a 27.72a

17.21 10.86 30.31 3.23 4.92 9.43

68.14ab 41.81a 212.11ab 14.45b 15.41a 28.82a

16.86 9.23 29.85 5.27 2.77 8.00

60.83b 50.41b 213.72b 14.95b 12.20b 21.17b

16.13 10.75 29.34 4.41 4.93 10.06

8.10** 10.50** 3.19* 6.89* 6.75* 12.44**

0.07 0.09 0.03 0.06 0.06 0.10

Note. IUS ¼ Intolerance of Uncertainty Scale; DTS ¼ Distress Tolerance Scale; MAT-50 ¼ Measure of Ambiguity Tolerance; DIS ¼ Discomfort Intolerance Scale; FDS ¼ Frustration-Discomfort Scale Discomfort Intolerance subscale; ASI ¼ Anxiety Sensitivity Index. Means that do not share a common superscript are statistically different at p , 0.05. *p , 0.05. **p , 0.001. c df ¼ 2. d Lower scores indicate greater intolerance.

from people with heightened depressive symptoms and people low in symptoms of GAD and depression on distress triggers. Relative to people low in GAD and depressive symptoms, people high in GAD symptoms reported significantly greater intolerance of uncertainty, negative emotions, ambiguity, frustration, and physical discomfort, as well as higher AS. Compared to individuals high in depressive symptoms, people high in GAD symptoms reported greater intolerance of physical discomfort. Furthermore, individuals high in depressive symptoms differed significantly from those low in GAD and depressive symptoms only in their intolerance of negative emotions and frustration, and on AS. The finding that the two clinical groups reported comparable intolerance for ambiguity was not predicted. Finally, although the distress intolerance dimensions collectively predicted group classification with a high degree of accuracy, only intolerance of physical discomfort uniquely predicted the presence of elevated GAD symptoms (versus elevated depressive symptoms and versus low GAD and depressive symptoms).

Implications for current conceptualizations of GAD Current theoretical models of GAD implicate IU and intolerance of negative emotions in pathological worry. In the current study, individuals with GAD reported greater IU and intolerance of negative emotions compared to those with low symptoms of GAD and depression. However, these facets of distress intolerance did not distinguish people high in GAD symptoms from those with high in depressive symptoms, suggesting that IU and intolerance of negative emotions may be transdiagnostic and more generally related to affective disorders. There is, however, a caveat to the suggestion that IU and intolerance of negative emotions are transdiagnostic. Current measures of distress intolerance may be too broad to capture what, specifically, is distressing about uncertainty and negative emotions for people with GAD. For example, Newman and Llera (2011) have argued that it may not be the experience of negative emotions that is distressing for people with GAD, but rather the shift from a neutral emotional state to one that is intensely negative. Thus, intolerance of negative emotions may cut across psychopathology, whereas difficulties withstanding negative emotional shifts may distinguish

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people with GAD from those with other psychopathologies. This is an avenue for future research. Intolerance of physical discomfort was the only distress intolerance dimension that differentiated people high in GAD symptoms from those in the comparison groups. Although GAD is typically conceptualized as a disorder of worry and anxiety, physical complaints are also part of the picture. People with GAD report muscle aches and gastrointestinal symptoms more than people with depression, and these symptoms can differentiate the two groups (Aldao, Mennin, Linardatos, & Fresco, 2010). A post-hoc analysis comparing the three groups in the current study on their reports of muscle tension on the GAD-Q-IV supports the aforementioned finding. People high in GAD symptoms were three times more likely to report muscle tension than participants low in GAD and depressive symptoms and two times more likely to report muscle tension than participants high in depressive symptoms. People with GAD also have other physical health conditions that can elicit painful and uncomfortable physical sensations. Compared to people without psychopathology, people with GAD have a higher incidence of migraines and chronic daily headaches (Mercante et al., 2011) and irritable bowel syndrome (Lee et al., 2009). Therefore, people with GAD not only experience more physical discomfort; it seems they also report that this form of discomfort is distressing. People with GAD engage in specific coping strategies to manage their physical discomfort. For example, they visit the emergency room more often than people without GAD (Jones, Ames, Jeffries, Scarinci, & Brantley, 2001). Further research on the reasons underlying their perceived inability to withstand and manage various aversive states and situations, and particularly physical discomfort, is warranted. Furthermore, given that people with heightened GAD symptoms were found to be elevated on all distress intolerance constructs compared to people low in symptoms of GAD and depression, it is important to consider the coping strategies that people with GAD may use to attenuate the distress from the various triggers. For example, people with GAD may engage in excessive information-seeking when experiencing distress secondary to uncertainty (Robichaud, 2013). Thus, more research is

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also needed on the coping repertoire of people with GAD to manage other triggers of distress.

Strengths and limitations The present study was a first step in understanding the specific triggers of distress in people high in GAD symptoms. This is the first known study to examine Zvolensky et al.’s (2010) conceptualization of distress intolerance in an analogue GAD sample. This is also the first known study to examine AS alongside Zvolensky et al.’s (2010) distress tolerance dimensions. In addition, the measures used in the present study were recommended by Leyro et al. (2010) and have been used extensively to investigate the distress intolerance constructs. The exclusive use of self-report measures of distress intolerance may be viewed as a limitation. A somewhat outdated (but previously widely used) version of the ASI was used in the present study. The newest AS measure, the Anxiety Sensitivity Index-3 (ASI-3; Taylor et al., 2007), is the best assessment of the three AS factors (Physical, Social, Cognitive; Wheaton, Deacon, McGrath, Berman, & Abramowitz, 2012), and it would be interesting to include this measure in future studies on distress intolerance. A study published after data collection for the present study ended found that the DIS may not be an optimal measure of intolerance of physical discomfort in undergraduate students (Luberto, Carle, & McLeish, 2013). It is hoped that future research will also seek to improve the properties of the DIS.

Future directions There are several avenues for future research. Replication with individuals with diagnosed GAD and depression is recommended. Although the distress intolerance constructs under investigation are statistically distinct, there is conceptual overlap. Additional research is needed to delineate the differences between the constructs in Zvolensky et al.’s (2010) model. While the present study examined individuals’ perceptions of their own ability to tolerate distress, research suggests that beliefs about the ability to handle aversive experiences or events may not always coincide with observable behavioural responses to these same experiences (e.g., on a cold-pressor task; Leyro et al., 2010). Understanding the relationship of perceptions of abilities to

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withstand distress and observed abilities to withstand distress in people with GAD could provide more insight into the veracity of their beliefs. Although our data provide a tentative suggestion that intolerance of physical discomfort is particular to GAD, the results also indicate that, relative to people low in affective symptoms, those high in GAD symptoms may be intolerant of a wide range of aversive experiences. Thus, more research is needed on the bounds of the distress intolerance of people with GAD and on the various ways in which they cope with their distress.

Conclusion The present study examined what types of experiences individuals with GAD find distressing. The findings contribute to the distress tolerance literature by highlighting that people with GAD report intolerance of various states and situations, and that intolerance of physical discomfort appears to have some specificity to GAD (versus depression). These findings are consistent with transdiagnostic conceptualizations of distress tolerance, but also suggest that certain experiences may be more distressing for people with specific types of psychopathology (Zvolensky et al., 2010). It is hoped that this research will support the refinement of GAD theories and stimulate research on the meaning and implications of physical discomfort for people high in pathological worry. Moreover, this is an important avenue of future research, as developing a better understanding of the triggers of distress can inform treatment of GAD.

Acknowledgements The authors would like to thank Carly Basian and Andrea Kusec for their valuable assistance with data collection and data entry. Disclosure statement: The authors have declared that no conflict of interest exists.

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