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Two facets of being bothered by bodily sensations: anxiety sensitivity and alexithymia in psychosomatic patients
Comprehensive Psychiatry 47 (2006) 489 – 495 www.elsevier.com/locate/comppsych
Two facets of being bothered by bodily sensations: anxiety sensitivity and alexithymia in psychosomatic patients Jochen Mueller4, Georg W. Alpers Department of Psychology, University of Wu¨rzburg, 97070 Wu¨rzburg, Germany
Abstract Objective: Anxiety sensitivity (AS) and alexithymia have common characteristics with regard to somatic sensations. The purpose of the present study is to investigate if both constructs are distinct or overlapping in a sample of psychosomatic inpatients. Methods: We analyzed the alexithymia scores of extreme groups who are high and low in AS and the correlations between both constructs in 204 patients. Results: As predicted, groups with high and low AS differed significantly in their Toronto Alexithymia Scale (TAS-20) scores. The correlations between the Anxiety Sensitivity Index and the TAS-20 were moderately high and were not significantly reduced if conceptually redundant items were removed from the TAS-20. A common factor analysis of the combined items of the Anxiety Sensitivity Index and the TAS-20 yielded no item overlap between the extracted factors of both measures. Conclusion: Results suggest that AS and alexithymia are related, but they are also distinct constructs. Therefore, it is important to assess AS and alexithymia separately. D 2006 Elsevier Inc. All rights reserved.
1. Introduction Anxiety sensitivity (AS) denotes individual differences in the fear of anxiety and in people’s beliefs about personal consequences when they experience anxiety symptoms. People high in AS fear anxiety-related bodily sensations and believe that anxiety experiences have negative implications or catastrophic consequences such as panic attacks, illness, embarrassment, additional anxiety, or loss of control. Thus, AS increases alertness to stimuli signaling the possibility of becoming anxious such as bodily sensations like trembling or heartbeat [1,2]. The Anxiety Sensitivity Index (ASI) [2] is the most frequently used instrument for measuring AS. A second construct, alexithymia, describes a set of related affective and cognitive characteristics: (a) difficulty in identifying feelings and distinguishing them from the bodily sensations of emotional arousal, (b) difficulty in describing feelings, (c) paucity of fantasies, and (d) a stimulus bound, externally orientated cognitive style [3]. The 20-item Toronto Alexithymia Scale (TAS-20) [4,5] is the most
4 Corresponding author. Tel.: +49 0 931 31 2970; fax: +49 0931 888 70 59. E-mail address: [email protected] (J. Mueller). 0010-440X/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.comppsych.2006.03.001
frequently used instrument for the assessment of alexithymia, and it measures the above-mentioned characteristics. Alexithymia and AS have common characteristics with regard to bodily sensations. Individuals with high alexithymia are prone to focus on the somatic sensations of emotional arousal, which may be misinterpreted as signs of physical illness [3]. Similarly, because of alertness to anxiety-related stimuli, individuals with high AS also show a proneness to focus on bodily sensations. It was argued that individuals high in AS would try to constrict their emotional experience to avoid the accompanying bodily sensations, which would result in elevated alexithymic tendencies [6]. Theoretically, there could be several reasons for a potential relation between both constructs. The relationship could be due to artifactual results (general risk or help-seeking), pathoplasty (one construct influencing the other), common causality (shared etiology), common pathological processes (manifestations on a spectrum), vulnerability (one is a risk factor for the other), and complication (one is the residual effect of the other) [7]. Empirically, AS and alexithymia are both related to trait anxiety and negative affectivity [1,8-10]. This suggests that AS and alexithymia may be closely related constructs. Several studies directly examined the relationship between
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AS and alexithymia. It was found that patients with panic disorder had higher scores in the ASI and the TAS compared with patients with obsessive-compulsive disorder [6]. However, in a second study, it was found that only the TAS-20 subscale ddifficulty identifying feelingsT and to a lesser degree ddifficulty describing feelingsT were significantly correlated with AS in patients with panic disorder [11]. Other studies showed that this relationship between AS and alexithymia was not restricted to patients with panic disorder. Cox et al [12] found that chronic pain patients high in alexithymia had higher ASI scores than patients low in alexithymia. It was argued that this might be because of overlapping items of the ASI and the TAS subscale ddifficulty identifying feelings.T This was not supported by a more recent study [13] where the relation between AS and alexithymia in a sample of psychology students was investigated. Similar to Cox et al [11], the authors found that the ASI scores were correlated only with the TAS-20 subscales ddifficulty identifying feelingsT and ddifficulty describing feelings.T However, the correlations persisted after removing 3 potentially overlapping items with the ASI from the TAS-20, casting doubt on the hypothesis that the relation between AS and alexithymia was merely an artifact by item overlap. However, the question of item overlap between the ASI and the TAS-20 is not answered satisfactorily, because the potential overlap of all items of the ASI and the TAS-20 has not been checked on item level. The purpose of the present study is to investigate if AS, as measured by the ASI, and alexithymia, as measured by TAS20, are distinct or are overlapping constructs. We sought to expand the findings of previous studies with patients with panic disorder and chronic pain to a sample of psychosomatic patients. In such a sample, we expected to find individuals with a large number of bodily symptoms potentially relevant for AS, as well as a high level of alexithymia. To this end, we analyzed the mean differences in the alexithymia scores of extreme groups high and low in self-rated AS and computed the correlations between AS and alexithymia. We expected that the group with high AS would show significantly larger alexithymia scores than the low AS group even after removing potentially overlapping items from the TAS-20. We further expected significant and moderate positive correlations between the constructs, which were not substantially reduced when removing conceptually redundant items from the TAS-20. Especially, the TAS-20 subscales ddifficulty identifying feelingsT and ddifficulty describing feelingsT were expected to correlate higher with AS than the subscale dexternally oriented thinkingT [6,13]. A further aim of the present study is to analyze the potential item overlap between the ASI and the TAS-20 more closely than had been done in earlier studies [11,13]. To accomplish this, we conducted a common principal component analysis of the combined items of the ASI and the TAS. Here, we expected a clear distinction between the items of the ASI and the TAS-20, as shown by no item overlap between the extracted factors of the 2 questionnaires.
2. Methods 2.1. Subjects and procedure The sample consisted of 204 patients (117 women) aged between 18 and 78 years (mean, 48.4; SD, 10.0) who were recruited at a hospital specializing in the treatment of psychosomatic disorders. Before entering the study, subjects provided written consent to participate. During the second week of their inpatient treatment, they were asked to complete a series of self-report questionnaires at a supervised group session. Diagnostic information was taken from the hospital medical records. Their primary International Classification of Diseases (ICD-10) diagnoses were primarily adjustment disorders, neurasthenia, other neurotic, stressrelated and somatoform disorders, affective disorders, and specific personality disorders. Regarding the educational level, 71.6% of the patients had finished 9 years of secondary school (bHauptschuleQ), 21.4% 10 years of junior high school (bRealschuleQ), and 7.0% 13 years of high school (bGymnasiumQ). 2.2. Instruments The means, standard deviations, and internal consistencies of the alexithymia questionnaires are displayed in Table 1. 2.2.1. ASI The ASI [2] was used in its German version [14] for the assessment of fear of anxiety or beliefs that anxiety experiences have negative implications. The self-report scale consists of 16 items that are summed to a total score, specifying a possible negative consequence (additional anxiety or fear, illness, embarrassment, and loss of control) to the experience of anxiety. Each item is rated on a 5-point Likert scale from 0 (very little) to 4 (very much). The mean ASI score in the present sample (mean, 27.89; SD, 13.77) lies within the norms of clinical samples with anxiety and Table 1 Pearson correlations between the anxiety sensitivity index and the TAS, with internal consistencies, means, and standard deviations of the TAS (N = 204) TAS-20
Mean (SD)
r
r cor
a
MIC
Total score Total score without items 3, 7, and 13 F1, difficulty identifying F1 without items 3, 7, and 13 F2, difficulty describing F3, external thinking
52.74 (12.86) 45.08 (10.57)
0.534 0.474
0.60 0.55
0.84 0.79
0.20 0.18
18.15 (6.69)
0.574
0.64
0.85
0.44
10.50 (4.00)
0.484
0.57
0.76
0.44
14.01 (4.22)
0.384
0.49
0.65
0.27
20.58 (4.89)
0.284
0.41
0.50
0.11
Note. r cor indicates correlations corrected for attenuation by unreliability. ASI: a = 0.93, MIC = 0.45. 4 P b .001.
J. Mueller, G.W. Alpers / Comprehensive Psychiatry 47 (2006) 489 – 495
panic disorders, phobias, and obsessive-compulsive disorders [1]. The internal consistency of the scale in the present study was very good (a = 0.93; mean inter-item correlation [MIC], 0.45). 2.2.2. TAS-20 The TAS-20 [4,5] was used for the self-report of alexithymia. This measure is widely accepted as the most valid and reliable available instrument for measuring alexithymia and is used in many different language versions [15,16]. Although the stability of this factor structure in different populations has been questioned by some authors [17,18], usually a 3-factor structure is interpreted [4,19]: F1, ddifficulty identifying feelings;T F2, ddifficulty describing feelings;T and F3, dexternally oriented thinking.T Each item is rated on a 5-point Likert scale from 1 to 5. Total scores of TAS less than 60 indicate alexithymia, and scores of TAS less than 52 points are contraindicative [15]. Applying the cutoff scores to the present sample, 63 patients (30.9%) would be classified as alexithymic and 102 patients (50.0%) as nonalexithymic. We used the German version of the TAS-20 [20]. 2.3. Statistical analyses 2.3.1. Extreme group comparisons Two extreme groups were created according to their ASI total scores. All patients scoring at least 1 SD above the sample mean (ASI N 41) constituted the group with high AS, whereas all patients scoring at least 1 SD below the sample mean (ASI b 15) were assigned to the group with low AS [13]. Differences in the alexithymia scores between the extreme groups were tested for significance by t tests for independent samples. The differences in the TAS-20 scores were further analyzed by removing 3 items (item 3, bI have physical sensations that even doctors don’t understand;Q item 7, bI am often puzzled by sensations in my body;Q item 13, bI don’t know what’s going on inside meQ) from the TAS that have been identified in earlier studies as potentially redundant with AS [11,13]. 2.3.2. Correlations The Pearson correlations between the ASI total score and the TAS-20 total score and subscales were computed. The correlation of the ASI with the TAS was further analyzed by removing the 3 items from the TAS potentially redundant with AS. Furthermore, the corrected correlations for attenuation by unreliability of the ASI and the alexithymia questionnaires were calculated [21]. 2.3.2. Principal component analysis To identify possible sources of overlap, we conducted a principal component analysis on the combined items of the ASI (16 items) and the TAS-20 (20 items). Because the components are assumed to be theoretically related, an oblique (Promax) rotation was applied. Only significant
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Table 2 ASI extreme group comparison: means, standard deviations, and results of t tests TAS-20
Total score Total score without items 3, 7, and 13 F1, difficulty identifying F1 without items 3, 7, and 13 F2, difficulty describing F3, external thinking
High AS (n = 42)
Low AS (n = 37)
t test
Mean (SD)
Mean (SD)
d
t(77)
P
64.88 (10.30) 54.14 (9.16)
45.11 (11.27) 39.81 (9.34)
1.83 1.55
8.15 6.88
.000 .000
24.37 (4.96)
13.22 (5.81)
2.07
9.21
.000
13.63 (3.21)
7.92 (3.70)
1.65
7.34
.000
17.29 (3.73)
12.84 (4.62)
1.07
4.73
.000
23.23 (4.62)
19.05 (4.72)
0.90
3.97
.000
Note. d indicates Cohen effect size. Extreme groups: high AS N 41 in ASI, low AS b 15 in ASI.
loadings (above 0.35) in the pattern matrix were interpreted [22]. The correlations of the resulting factors were interpreted using the factor correlation matrix. The KaiserMeyer-Olkin measure for sampling adequacy (KMO = 0.89), the Bartlett test of sphericity (v 2 = 3453.3, df = 630, P b .001), and the anti-image correlations with the measures of sampling adequacy all suggested that the data were well suited for factor analysis.
3. Results 3.1. Extreme group comparisons We first examined the prediction that patients high and low in AS would differ significantly in their alexithymia scores. As Table 2 shows, the group with high AS had significantly higher scores in all scales of the TAS-20. The mean of the TAS-20 total score of the group with high AS (mean, 64.88) was within alexithymic range (TAS N60), whereas that for the low AS group (mean, 45.11) lay within the nonalexithymic range (TAS b 52). The effect sizes of the mean differences were all large. As expected, the largest differences occurred in the TAS total score (d = 1.83) and the factor ddifficulties identifying feelingsT (d = 2.07). In addition, following our expectations, the differences were not substantially reduced and remained significant when the potentially redundant items with the ASI were removed (d = 1.55 and 1.65, respectively). The smallest difference with still a large effect size (d = 0.90) was found for the TAS subscale dexternally oriented thinking.T 3.2. Correlations between AS and alexithymia Because both AS and alexithymia are dimensional constructs and because forming extreme groups reduces statistical power, we next investigated the relation between
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Table 3 Factor loadings of the pooled ASI and TAS items Item F1, AS ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI F2, difficulty identifying feelings TAS TAS TAS TAS TAS TAS TAS TAS TAS TAS F3, lack of importance of emotions TAS TAS TAS TAS F4, externally oriented thinking TAS TAS TAS TAS TAS Eigenvalues Percentage of explained variance
Item content
F1
14 10 16 6 9 15 3 12 4 8 11 13 7 2 1 5
Scared by unusual bodily sensations Scared by shortness of breath Scared by nervousness Scared by rapid heartbeat Worry about rapid heartbeat Worry about mental illness Scared by trembling Scared by lack of concentration Scared by feeling faint Scared by nausea Worry about upset stomach Noticing feeling shaky Embarrassment by stomach growl Worry to go crazy Appearing nervous Importance to control emotions
0.85 0.83 0.79 0.78 0.77 0.74 0.73 0.70 0.69 0.69 0.68 0.59 0.58 0.57 0.49 0.46
13 9 14 1 2 6 8 11 7 3
Understanding inner processes Identification of feelings Understanding feelings Confusion about emotions Expression of feelings Distinction of feelings Pragmatic thinking Description of feelings for others Puzzling bodily sensations Unexplained bodily sensations
10 19 18 4
Importance of emotions Examination of feelings Feeling of closeness to others Description of own feelings
15 16 17 5 12
Talking about daily activities Watch blightQ entertainment shows Revealing feelings to friends Analyzing problems Describe feelings more
F2
F3
F4
0.84 0.84 0.66 0.65 0.65 0.62 0.60 0.58 0.53 0.37 0.76 0.75 0.66 0.47
0.41 0.41 10.53 29.24
3.13 8.70
2.19 6.07
0.75 0.61 0.55 0.43 0.36 1.74 4.83
Note. Only significant loadings (above 0.35) of the pattern matrix are shown. TAS item 20 did not load significantly on factor 4.
AS and alexithymia continuously in the whole sample. The correlations between the ASI and the TAS-20 are displayed in Table 1. As expected, there was a certain degree of relationship between AS and alexithymia. Table 1 shows that the TAS total score and all subscales were significantly correlated with the ASI. As predicted, the largest correlations with moderate size were found with the TAS total score and the bdifficulty identifying feelingsQ subscale, whereas correlations with the subscales bdifficulty describing feelingsQ and bexternally oriented thinkingQ were of small to medium size. The significant moderate correlations of the ASI with the TAS could be partly caused by the potentially redundant items with the ASI. Therefore, we next analyzed if the correlations between the ASI and TAS would be reduced if the redundant items were removed from the
TAS. As expected, this was not the case, although the size of the corrected values decreased. The correlations between the ASI and the TAS total scores (r = 0.53) and between the ASI and the TAS total score without items 3, 7, and 13 (r = 0.47) were not significantly different from each other (Z = 0.80, P = 0.42). Similarly, the correlations between the ASI and TAS F1 ddifficulty identifying feelingsT (r = 0.57) and between the ASI and TAS F1 without items 3, 7, and 13 (r = 0.48) did not differ significantly (Z = 1.25, P = 0.21). 3.3. Item overlap To more closely examine the relationship between AS and alexithymia on the item level, we analyzed the item overlap of the ASI and the TAS-20 in a principal component analysis of the pooled items of both questionnaires.
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Examination of the Screen test, the Parallel analysis method, and Velicer’s Minimum Average Partial test [23] suggested a 4-factor structure (cf. Table 2). As expected, within each of these factors, there was no overlap between the items of the ASI and the TAS. The first factor consisted of all 16 items of the ASI and can be labeled dAS.T The marker item with the highest loading on this factor was item 14 (bunusual body sensations scare meQ), which is the core of AS. The second factor consisted of 10 items of the TAS describing primarily difficulties identifying feelings. The marker items of this factor were TAS item 13 (bI don’t know what’s going on inside meQ) and item 9 (bI have feelings that I can’t quite identifyQ). All of the items that were identified as potentially redundant with the ASI in earlier studies (items 3, 7, 13) loaded on this factor. The remaining 2 factors consisted primarily of items from the dexternally oriented thinkingT facet of alexithymia. The third factor contained 4 items of the TAS and was named dlack of importance of emotionsT with the marker item 10 (bbeing in touch with emotions is essentialQ). Finally, the fourth factor consisted of 4 items of the TAS covering dexternally oriented thinkingT with the marker item 15 (bI prefer talking to people about their daily activities rather than their feelingsQ). TAS item 20 (blooking for hidden meanings in movies or plays distracts from their enjoymentQ) did not load significantly on this factor. This is in accordance with an earlier study where we observed that item 20 did not load significantly on any factor [24]. Item 5 (bI prefer to analyze problems rather than just describe themQ) and 17 (bit is difficult for me to reveal my innermost feelings, even to close friendsQ) of the TAS were the only items with a significant cross-loading on 2 factors (2 and 4). Surprisingly, item 5 loaded negatively on factor 4; hence, it may be better assigned to factor 2 where it loaded positively and is about equally high. The 4 extracted factors accounted for a total of 48.8% of the explained variance. Factor loadings of the pooled ASI and TAS items are reported in Table 3. The only substantial correlation between the factors obtained from the principal component analysis was of medium size (r = 0.50) and occurred between factor 1 (bASQ) and 2 (bdifficulty identifying feelingsQ). This corroborates our findings from the correlation analysis and shows that it is mainly the facet ddifficulty identifying feelingsT of alexithymia which is related to AS. All other correlations were close to zero (F1-F3, r = 0.04; F1-F4, r = 0.13; F2-F3, r = 0.13; F2-F4, r = 0.18; F3-F4, r = 0.06). 4. Discussion The detailed analysis of this study in psychosomatic inpatients suggests that AS and alexithymia are related, but they are also distinct constructs. The first argument for their relatedness is that groups with high and low AS differed significantly in their TAS scores. Second, also as expected,
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AS and alexithymia were moderately positively correlated. On the other hand, the first argument for their distinctness is that these correlations are only moderately high with the lowest correlations between the ASI and the dexternally oriented thinkingT subscale of the TAS-20. Second, the correlations were not significantly reduced if conceptually redundant items were removed from the TAS-20. Third, a principal component analysis of the pooled items of the ASI and the TAS-20 yielded no item overlap between the extracted factors of both measures. Again, the correlations between the first factor containing all items of the ASI and the second factor comprising items mainly from ddifficulty identifying feelingsT were moderately high. The finding that the group with high AS had higher TAS20 total scores than the group with low AS confirms earlier findings with patients with chronic pain [12] and psychology students [13]. Extending these earlier findings, as expected, we found that the largest mean differences occurred for the TAS-20 subscale ddifficulty identifying feelings.T Because the mean differences were not substantially reduced after removing potentially redundant items from the TAS-20, we obtained first indications that the group differences were not merely an artifact of item overlap. All correlations between the ASI and the TAS-20 were significant. Corroborating the findings from the extreme group comparison, the largest correlations were of medium size were found for the total score and the subscale ddifficulty identifying feelings.T The subscale dexternally oriented thinkingT was only weakly correlated with the ASI. This finding confirms the results of earlier studies on patients with panic disorder [11] and psychology students [13]. As was already shown in the latter study, the correlations of the present study were not significantly reduced when the potentially redundant items from the TAS20 were removed. To analyze in more detail the potential overlap of items of the ASI and the TAS-20 than what has been done by Devine et al [13], we conducted a principal component analysis of the pooled items of both measures. As expected, there was no overlap between the items of the 4 extracted factors of the ASI and the TAS-20. This is a strong indication that both instruments can be distinguished on the content level and suggests that AS and alexithymia are related but are distinct constructs. Therefore, the picture is different for AS than for trait anxiety. Items measuring anxiety (Hospital Anxiety and Depression Scale [HADS]) and items of the TAS ddifficulty identifying feelingsT subscale loaded on 1 factor in a combined principal component analysis of another study [9]. In our principal component analysis, the first extracted factor consisted of all items of the ASI. This supports using the total score as a measure of AS and is in agreement with many other previous studies where a 1-factor structure of the ASI was found [25]. The other 3 factors are composed of items of the TAS-20 only, but these factors were not exactly
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the same factors that were proposed by Bagby et al [4]. However, it is not unusual that the factor structures of student and patient samples of the TAS-20 differ [18]. The second factor consisted mainly of items describing difficulties identifying feelings and is very similar to the first factor found in a sample of psychosomatic patients and alcoholics [24]. Interestingly, all of the 3 TAS-20 items that had been thought of as potentially redundant with the ASI loaded on the second factor of the present study, with no significant cross-loadings on factor 1. This suggests that these items cannot be regarded as redundant with the ASI. However, the moderate correlation between factor 1 and 2 shows that AS and alexithymia as measured by factor 2 (and not by factor 3 or 4) are moderately related. The relationship between AS and ddifficulties identifying feelingsT may be clinically relevant. Patients high in AS are known to have an increased risk to develop panic disorder [26]. If they find it difficult to identify their feelings, they may need special encouragement to explore their feelings and find appropriate help in preventing further escalation into panic disorder. Using experimental procedures with implicit measures, in addition to self-report, may help to circumvent the problem of not being able to measure feelings that are difficult to identify (see Mqller et al [27]). In conclusion, the results of the present study clearly show that AS and alexithymia are distinct constructs, which are related to a certain degree. This relationship is not merely caused by a methodological artifact of conceptually overlapping or redundant items. Instead, the link between the 2 constructs may be the patient’s focusing on bodily sensations and the misinterpretation as signs of illness, with which ddifficulty identifyingT feelings is especially related. This is supported by data showing a moderate relationship between bodily symptom reporting and the alexithymia facet of ddifficulty identifying feelingsT, but not externally oriented thinking (see De Gucht and Heisser [28] for a review). Therefore, it is important to assess AS and alexithymia separately. Furthermore, the present study shows that the relationship between AS and alexithymia is not only restricted to patients with panic disorder and social phobia, patients with chronic pain or psychology students, but also holds for psychosomatic patients. Acknowledgment We thank Norman Reim and Holger Sqg from the Klinikum Bad Bocklet for the help in the collection of the data, and Heiner Ellgring and Paul Pauli for their support. References [1] Peterson RA, Reiss S. Anxiety sensitivity index revised test manual. Worthington (Ohio)7 IDS Publishing; 1993. [2] Reiss S, Peterson RA, Gursky DM, McNally RJ. Anxiety sensitivity, anxiety frequency and the prediction of fearfulness. Behav Res Ther 1986;24:1 - 8.
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[26] Plehn K, Peterson RA. Anxiety sensitivity as a predictor of the development of panic symptoms, panic attacks, and panic disorder: a prospective study. J Anxiety Disord 2002;16:455 - 74. [27] Mqller J, Alpers GW, Reim N. Dissociation of rated emotional valence and Stroop interference in observer-rated alexithymia. J Psychosom Res [in press]. [28] De Gucht V, Heisser W. Alexithymia and somatisation. A quantitative review of the literature. J Psychosom Res 2003;54:425 - 34.
Two facets of being bothered by bodily sensations: anxiety sensitivity and alexithymia in psychosomatic patients Jochen Mueller4, Georg W. Alpers Department of Psychology, University of Wu¨rzburg, 97070 Wu¨rzburg, Germany
Abstract Objective: Anxiety sensitivity (AS) and alexithymia have common characteristics with regard to somatic sensations. The purpose of the present study is to investigate if both constructs are distinct or overlapping in a sample of psychosomatic inpatients. Methods: We analyzed the alexithymia scores of extreme groups who are high and low in AS and the correlations between both constructs in 204 patients. Results: As predicted, groups with high and low AS differed significantly in their Toronto Alexithymia Scale (TAS-20) scores. The correlations between the Anxiety Sensitivity Index and the TAS-20 were moderately high and were not significantly reduced if conceptually redundant items were removed from the TAS-20. A common factor analysis of the combined items of the Anxiety Sensitivity Index and the TAS-20 yielded no item overlap between the extracted factors of both measures. Conclusion: Results suggest that AS and alexithymia are related, but they are also distinct constructs. Therefore, it is important to assess AS and alexithymia separately. D 2006 Elsevier Inc. All rights reserved.
1. Introduction Anxiety sensitivity (AS) denotes individual differences in the fear of anxiety and in people’s beliefs about personal consequences when they experience anxiety symptoms. People high in AS fear anxiety-related bodily sensations and believe that anxiety experiences have negative implications or catastrophic consequences such as panic attacks, illness, embarrassment, additional anxiety, or loss of control. Thus, AS increases alertness to stimuli signaling the possibility of becoming anxious such as bodily sensations like trembling or heartbeat [1,2]. The Anxiety Sensitivity Index (ASI) [2] is the most frequently used instrument for measuring AS. A second construct, alexithymia, describes a set of related affective and cognitive characteristics: (a) difficulty in identifying feelings and distinguishing them from the bodily sensations of emotional arousal, (b) difficulty in describing feelings, (c) paucity of fantasies, and (d) a stimulus bound, externally orientated cognitive style [3]. The 20-item Toronto Alexithymia Scale (TAS-20) [4,5] is the most
4 Corresponding author. Tel.: +49 0 931 31 2970; fax: +49 0931 888 70 59. E-mail address: [email protected] (J. Mueller). 0010-440X/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.comppsych.2006.03.001
frequently used instrument for the assessment of alexithymia, and it measures the above-mentioned characteristics. Alexithymia and AS have common characteristics with regard to bodily sensations. Individuals with high alexithymia are prone to focus on the somatic sensations of emotional arousal, which may be misinterpreted as signs of physical illness [3]. Similarly, because of alertness to anxiety-related stimuli, individuals with high AS also show a proneness to focus on bodily sensations. It was argued that individuals high in AS would try to constrict their emotional experience to avoid the accompanying bodily sensations, which would result in elevated alexithymic tendencies [6]. Theoretically, there could be several reasons for a potential relation between both constructs. The relationship could be due to artifactual results (general risk or help-seeking), pathoplasty (one construct influencing the other), common causality (shared etiology), common pathological processes (manifestations on a spectrum), vulnerability (one is a risk factor for the other), and complication (one is the residual effect of the other) [7]. Empirically, AS and alexithymia are both related to trait anxiety and negative affectivity [1,8-10]. This suggests that AS and alexithymia may be closely related constructs. Several studies directly examined the relationship between
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AS and alexithymia. It was found that patients with panic disorder had higher scores in the ASI and the TAS compared with patients with obsessive-compulsive disorder [6]. However, in a second study, it was found that only the TAS-20 subscale ddifficulty identifying feelingsT and to a lesser degree ddifficulty describing feelingsT were significantly correlated with AS in patients with panic disorder [11]. Other studies showed that this relationship between AS and alexithymia was not restricted to patients with panic disorder. Cox et al [12] found that chronic pain patients high in alexithymia had higher ASI scores than patients low in alexithymia. It was argued that this might be because of overlapping items of the ASI and the TAS subscale ddifficulty identifying feelings.T This was not supported by a more recent study [13] where the relation between AS and alexithymia in a sample of psychology students was investigated. Similar to Cox et al [11], the authors found that the ASI scores were correlated only with the TAS-20 subscales ddifficulty identifying feelingsT and ddifficulty describing feelings.T However, the correlations persisted after removing 3 potentially overlapping items with the ASI from the TAS-20, casting doubt on the hypothesis that the relation between AS and alexithymia was merely an artifact by item overlap. However, the question of item overlap between the ASI and the TAS-20 is not answered satisfactorily, because the potential overlap of all items of the ASI and the TAS-20 has not been checked on item level. The purpose of the present study is to investigate if AS, as measured by the ASI, and alexithymia, as measured by TAS20, are distinct or are overlapping constructs. We sought to expand the findings of previous studies with patients with panic disorder and chronic pain to a sample of psychosomatic patients. In such a sample, we expected to find individuals with a large number of bodily symptoms potentially relevant for AS, as well as a high level of alexithymia. To this end, we analyzed the mean differences in the alexithymia scores of extreme groups high and low in self-rated AS and computed the correlations between AS and alexithymia. We expected that the group with high AS would show significantly larger alexithymia scores than the low AS group even after removing potentially overlapping items from the TAS-20. We further expected significant and moderate positive correlations between the constructs, which were not substantially reduced when removing conceptually redundant items from the TAS-20. Especially, the TAS-20 subscales ddifficulty identifying feelingsT and ddifficulty describing feelingsT were expected to correlate higher with AS than the subscale dexternally oriented thinkingT [6,13]. A further aim of the present study is to analyze the potential item overlap between the ASI and the TAS-20 more closely than had been done in earlier studies [11,13]. To accomplish this, we conducted a common principal component analysis of the combined items of the ASI and the TAS. Here, we expected a clear distinction between the items of the ASI and the TAS-20, as shown by no item overlap between the extracted factors of the 2 questionnaires.
2. Methods 2.1. Subjects and procedure The sample consisted of 204 patients (117 women) aged between 18 and 78 years (mean, 48.4; SD, 10.0) who were recruited at a hospital specializing in the treatment of psychosomatic disorders. Before entering the study, subjects provided written consent to participate. During the second week of their inpatient treatment, they were asked to complete a series of self-report questionnaires at a supervised group session. Diagnostic information was taken from the hospital medical records. Their primary International Classification of Diseases (ICD-10) diagnoses were primarily adjustment disorders, neurasthenia, other neurotic, stressrelated and somatoform disorders, affective disorders, and specific personality disorders. Regarding the educational level, 71.6% of the patients had finished 9 years of secondary school (bHauptschuleQ), 21.4% 10 years of junior high school (bRealschuleQ), and 7.0% 13 years of high school (bGymnasiumQ). 2.2. Instruments The means, standard deviations, and internal consistencies of the alexithymia questionnaires are displayed in Table 1. 2.2.1. ASI The ASI [2] was used in its German version [14] for the assessment of fear of anxiety or beliefs that anxiety experiences have negative implications. The self-report scale consists of 16 items that are summed to a total score, specifying a possible negative consequence (additional anxiety or fear, illness, embarrassment, and loss of control) to the experience of anxiety. Each item is rated on a 5-point Likert scale from 0 (very little) to 4 (very much). The mean ASI score in the present sample (mean, 27.89; SD, 13.77) lies within the norms of clinical samples with anxiety and Table 1 Pearson correlations between the anxiety sensitivity index and the TAS, with internal consistencies, means, and standard deviations of the TAS (N = 204) TAS-20
Mean (SD)
r
r cor
a
MIC
Total score Total score without items 3, 7, and 13 F1, difficulty identifying F1 without items 3, 7, and 13 F2, difficulty describing F3, external thinking
52.74 (12.86) 45.08 (10.57)
0.534 0.474
0.60 0.55
0.84 0.79
0.20 0.18
18.15 (6.69)
0.574
0.64
0.85
0.44
10.50 (4.00)
0.484
0.57
0.76
0.44
14.01 (4.22)
0.384
0.49
0.65
0.27
20.58 (4.89)
0.284
0.41
0.50
0.11
Note. r cor indicates correlations corrected for attenuation by unreliability. ASI: a = 0.93, MIC = 0.45. 4 P b .001.
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panic disorders, phobias, and obsessive-compulsive disorders [1]. The internal consistency of the scale in the present study was very good (a = 0.93; mean inter-item correlation [MIC], 0.45). 2.2.2. TAS-20 The TAS-20 [4,5] was used for the self-report of alexithymia. This measure is widely accepted as the most valid and reliable available instrument for measuring alexithymia and is used in many different language versions [15,16]. Although the stability of this factor structure in different populations has been questioned by some authors [17,18], usually a 3-factor structure is interpreted [4,19]: F1, ddifficulty identifying feelings;T F2, ddifficulty describing feelings;T and F3, dexternally oriented thinking.T Each item is rated on a 5-point Likert scale from 1 to 5. Total scores of TAS less than 60 indicate alexithymia, and scores of TAS less than 52 points are contraindicative [15]. Applying the cutoff scores to the present sample, 63 patients (30.9%) would be classified as alexithymic and 102 patients (50.0%) as nonalexithymic. We used the German version of the TAS-20 [20]. 2.3. Statistical analyses 2.3.1. Extreme group comparisons Two extreme groups were created according to their ASI total scores. All patients scoring at least 1 SD above the sample mean (ASI N 41) constituted the group with high AS, whereas all patients scoring at least 1 SD below the sample mean (ASI b 15) were assigned to the group with low AS [13]. Differences in the alexithymia scores between the extreme groups were tested for significance by t tests for independent samples. The differences in the TAS-20 scores were further analyzed by removing 3 items (item 3, bI have physical sensations that even doctors don’t understand;Q item 7, bI am often puzzled by sensations in my body;Q item 13, bI don’t know what’s going on inside meQ) from the TAS that have been identified in earlier studies as potentially redundant with AS [11,13]. 2.3.2. Correlations The Pearson correlations between the ASI total score and the TAS-20 total score and subscales were computed. The correlation of the ASI with the TAS was further analyzed by removing the 3 items from the TAS potentially redundant with AS. Furthermore, the corrected correlations for attenuation by unreliability of the ASI and the alexithymia questionnaires were calculated [21]. 2.3.2. Principal component analysis To identify possible sources of overlap, we conducted a principal component analysis on the combined items of the ASI (16 items) and the TAS-20 (20 items). Because the components are assumed to be theoretically related, an oblique (Promax) rotation was applied. Only significant
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Table 2 ASI extreme group comparison: means, standard deviations, and results of t tests TAS-20
Total score Total score without items 3, 7, and 13 F1, difficulty identifying F1 without items 3, 7, and 13 F2, difficulty describing F3, external thinking
High AS (n = 42)
Low AS (n = 37)
t test
Mean (SD)
Mean (SD)
d
t(77)
P
64.88 (10.30) 54.14 (9.16)
45.11 (11.27) 39.81 (9.34)
1.83 1.55
8.15 6.88
.000 .000
24.37 (4.96)
13.22 (5.81)
2.07
9.21
.000
13.63 (3.21)
7.92 (3.70)
1.65
7.34
.000
17.29 (3.73)
12.84 (4.62)
1.07
4.73
.000
23.23 (4.62)
19.05 (4.72)
0.90
3.97
.000
Note. d indicates Cohen effect size. Extreme groups: high AS N 41 in ASI, low AS b 15 in ASI.
loadings (above 0.35) in the pattern matrix were interpreted [22]. The correlations of the resulting factors were interpreted using the factor correlation matrix. The KaiserMeyer-Olkin measure for sampling adequacy (KMO = 0.89), the Bartlett test of sphericity (v 2 = 3453.3, df = 630, P b .001), and the anti-image correlations with the measures of sampling adequacy all suggested that the data were well suited for factor analysis.
3. Results 3.1. Extreme group comparisons We first examined the prediction that patients high and low in AS would differ significantly in their alexithymia scores. As Table 2 shows, the group with high AS had significantly higher scores in all scales of the TAS-20. The mean of the TAS-20 total score of the group with high AS (mean, 64.88) was within alexithymic range (TAS N60), whereas that for the low AS group (mean, 45.11) lay within the nonalexithymic range (TAS b 52). The effect sizes of the mean differences were all large. As expected, the largest differences occurred in the TAS total score (d = 1.83) and the factor ddifficulties identifying feelingsT (d = 2.07). In addition, following our expectations, the differences were not substantially reduced and remained significant when the potentially redundant items with the ASI were removed (d = 1.55 and 1.65, respectively). The smallest difference with still a large effect size (d = 0.90) was found for the TAS subscale dexternally oriented thinking.T 3.2. Correlations between AS and alexithymia Because both AS and alexithymia are dimensional constructs and because forming extreme groups reduces statistical power, we next investigated the relation between
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Table 3 Factor loadings of the pooled ASI and TAS items Item F1, AS ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI ASI F2, difficulty identifying feelings TAS TAS TAS TAS TAS TAS TAS TAS TAS TAS F3, lack of importance of emotions TAS TAS TAS TAS F4, externally oriented thinking TAS TAS TAS TAS TAS Eigenvalues Percentage of explained variance
Item content
F1
14 10 16 6 9 15 3 12 4 8 11 13 7 2 1 5
Scared by unusual bodily sensations Scared by shortness of breath Scared by nervousness Scared by rapid heartbeat Worry about rapid heartbeat Worry about mental illness Scared by trembling Scared by lack of concentration Scared by feeling faint Scared by nausea Worry about upset stomach Noticing feeling shaky Embarrassment by stomach growl Worry to go crazy Appearing nervous Importance to control emotions
0.85 0.83 0.79 0.78 0.77 0.74 0.73 0.70 0.69 0.69 0.68 0.59 0.58 0.57 0.49 0.46
13 9 14 1 2 6 8 11 7 3
Understanding inner processes Identification of feelings Understanding feelings Confusion about emotions Expression of feelings Distinction of feelings Pragmatic thinking Description of feelings for others Puzzling bodily sensations Unexplained bodily sensations
10 19 18 4
Importance of emotions Examination of feelings Feeling of closeness to others Description of own feelings
15 16 17 5 12
Talking about daily activities Watch blightQ entertainment shows Revealing feelings to friends Analyzing problems Describe feelings more
F2
F3
F4
0.84 0.84 0.66 0.65 0.65 0.62 0.60 0.58 0.53 0.37 0.76 0.75 0.66 0.47
0.41 0.41 10.53 29.24
3.13 8.70
2.19 6.07
0.75 0.61 0.55 0.43 0.36 1.74 4.83
Note. Only significant loadings (above 0.35) of the pattern matrix are shown. TAS item 20 did not load significantly on factor 4.
AS and alexithymia continuously in the whole sample. The correlations between the ASI and the TAS-20 are displayed in Table 1. As expected, there was a certain degree of relationship between AS and alexithymia. Table 1 shows that the TAS total score and all subscales were significantly correlated with the ASI. As predicted, the largest correlations with moderate size were found with the TAS total score and the bdifficulty identifying feelingsQ subscale, whereas correlations with the subscales bdifficulty describing feelingsQ and bexternally oriented thinkingQ were of small to medium size. The significant moderate correlations of the ASI with the TAS could be partly caused by the potentially redundant items with the ASI. Therefore, we next analyzed if the correlations between the ASI and TAS would be reduced if the redundant items were removed from the
TAS. As expected, this was not the case, although the size of the corrected values decreased. The correlations between the ASI and the TAS total scores (r = 0.53) and between the ASI and the TAS total score without items 3, 7, and 13 (r = 0.47) were not significantly different from each other (Z = 0.80, P = 0.42). Similarly, the correlations between the ASI and TAS F1 ddifficulty identifying feelingsT (r = 0.57) and between the ASI and TAS F1 without items 3, 7, and 13 (r = 0.48) did not differ significantly (Z = 1.25, P = 0.21). 3.3. Item overlap To more closely examine the relationship between AS and alexithymia on the item level, we analyzed the item overlap of the ASI and the TAS-20 in a principal component analysis of the pooled items of both questionnaires.
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Examination of the Screen test, the Parallel analysis method, and Velicer’s Minimum Average Partial test [23] suggested a 4-factor structure (cf. Table 2). As expected, within each of these factors, there was no overlap between the items of the ASI and the TAS. The first factor consisted of all 16 items of the ASI and can be labeled dAS.T The marker item with the highest loading on this factor was item 14 (bunusual body sensations scare meQ), which is the core of AS. The second factor consisted of 10 items of the TAS describing primarily difficulties identifying feelings. The marker items of this factor were TAS item 13 (bI don’t know what’s going on inside meQ) and item 9 (bI have feelings that I can’t quite identifyQ). All of the items that were identified as potentially redundant with the ASI in earlier studies (items 3, 7, 13) loaded on this factor. The remaining 2 factors consisted primarily of items from the dexternally oriented thinkingT facet of alexithymia. The third factor contained 4 items of the TAS and was named dlack of importance of emotionsT with the marker item 10 (bbeing in touch with emotions is essentialQ). Finally, the fourth factor consisted of 4 items of the TAS covering dexternally oriented thinkingT with the marker item 15 (bI prefer talking to people about their daily activities rather than their feelingsQ). TAS item 20 (blooking for hidden meanings in movies or plays distracts from their enjoymentQ) did not load significantly on this factor. This is in accordance with an earlier study where we observed that item 20 did not load significantly on any factor [24]. Item 5 (bI prefer to analyze problems rather than just describe themQ) and 17 (bit is difficult for me to reveal my innermost feelings, even to close friendsQ) of the TAS were the only items with a significant cross-loading on 2 factors (2 and 4). Surprisingly, item 5 loaded negatively on factor 4; hence, it may be better assigned to factor 2 where it loaded positively and is about equally high. The 4 extracted factors accounted for a total of 48.8% of the explained variance. Factor loadings of the pooled ASI and TAS items are reported in Table 3. The only substantial correlation between the factors obtained from the principal component analysis was of medium size (r = 0.50) and occurred between factor 1 (bASQ) and 2 (bdifficulty identifying feelingsQ). This corroborates our findings from the correlation analysis and shows that it is mainly the facet ddifficulty identifying feelingsT of alexithymia which is related to AS. All other correlations were close to zero (F1-F3, r = 0.04; F1-F4, r = 0.13; F2-F3, r = 0.13; F2-F4, r = 0.18; F3-F4, r = 0.06). 4. Discussion The detailed analysis of this study in psychosomatic inpatients suggests that AS and alexithymia are related, but they are also distinct constructs. The first argument for their relatedness is that groups with high and low AS differed significantly in their TAS scores. Second, also as expected,
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AS and alexithymia were moderately positively correlated. On the other hand, the first argument for their distinctness is that these correlations are only moderately high with the lowest correlations between the ASI and the dexternally oriented thinkingT subscale of the TAS-20. Second, the correlations were not significantly reduced if conceptually redundant items were removed from the TAS-20. Third, a principal component analysis of the pooled items of the ASI and the TAS-20 yielded no item overlap between the extracted factors of both measures. Again, the correlations between the first factor containing all items of the ASI and the second factor comprising items mainly from ddifficulty identifying feelingsT were moderately high. The finding that the group with high AS had higher TAS20 total scores than the group with low AS confirms earlier findings with patients with chronic pain [12] and psychology students [13]. Extending these earlier findings, as expected, we found that the largest mean differences occurred for the TAS-20 subscale ddifficulty identifying feelings.T Because the mean differences were not substantially reduced after removing potentially redundant items from the TAS-20, we obtained first indications that the group differences were not merely an artifact of item overlap. All correlations between the ASI and the TAS-20 were significant. Corroborating the findings from the extreme group comparison, the largest correlations were of medium size were found for the total score and the subscale ddifficulty identifying feelings.T The subscale dexternally oriented thinkingT was only weakly correlated with the ASI. This finding confirms the results of earlier studies on patients with panic disorder [11] and psychology students [13]. As was already shown in the latter study, the correlations of the present study were not significantly reduced when the potentially redundant items from the TAS20 were removed. To analyze in more detail the potential overlap of items of the ASI and the TAS-20 than what has been done by Devine et al [13], we conducted a principal component analysis of the pooled items of both measures. As expected, there was no overlap between the items of the 4 extracted factors of the ASI and the TAS-20. This is a strong indication that both instruments can be distinguished on the content level and suggests that AS and alexithymia are related but are distinct constructs. Therefore, the picture is different for AS than for trait anxiety. Items measuring anxiety (Hospital Anxiety and Depression Scale [HADS]) and items of the TAS ddifficulty identifying feelingsT subscale loaded on 1 factor in a combined principal component analysis of another study [9]. In our principal component analysis, the first extracted factor consisted of all items of the ASI. This supports using the total score as a measure of AS and is in agreement with many other previous studies where a 1-factor structure of the ASI was found [25]. The other 3 factors are composed of items of the TAS-20 only, but these factors were not exactly
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the same factors that were proposed by Bagby et al [4]. However, it is not unusual that the factor structures of student and patient samples of the TAS-20 differ [18]. The second factor consisted mainly of items describing difficulties identifying feelings and is very similar to the first factor found in a sample of psychosomatic patients and alcoholics [24]. Interestingly, all of the 3 TAS-20 items that had been thought of as potentially redundant with the ASI loaded on the second factor of the present study, with no significant cross-loadings on factor 1. This suggests that these items cannot be regarded as redundant with the ASI. However, the moderate correlation between factor 1 and 2 shows that AS and alexithymia as measured by factor 2 (and not by factor 3 or 4) are moderately related. The relationship between AS and ddifficulties identifying feelingsT may be clinically relevant. Patients high in AS are known to have an increased risk to develop panic disorder [26]. If they find it difficult to identify their feelings, they may need special encouragement to explore their feelings and find appropriate help in preventing further escalation into panic disorder. Using experimental procedures with implicit measures, in addition to self-report, may help to circumvent the problem of not being able to measure feelings that are difficult to identify (see Mqller et al [27]). In conclusion, the results of the present study clearly show that AS and alexithymia are distinct constructs, which are related to a certain degree. This relationship is not merely caused by a methodological artifact of conceptually overlapping or redundant items. Instead, the link between the 2 constructs may be the patient’s focusing on bodily sensations and the misinterpretation as signs of illness, with which ddifficulty identifyingT feelings is especially related. This is supported by data showing a moderate relationship between bodily symptom reporting and the alexithymia facet of ddifficulty identifying feelingsT, but not externally oriented thinking (see De Gucht and Heisser [28] for a review). Therefore, it is important to assess AS and alexithymia separately. Furthermore, the present study shows that the relationship between AS and alexithymia is not only restricted to patients with panic disorder and social phobia, patients with chronic pain or psychology students, but also holds for psychosomatic patients. Acknowledgment We thank Norman Reim and Holger Sqg from the Klinikum Bad Bocklet for the help in the collection of the data, and Heiner Ellgring and Paul Pauli for their support. References [1] Peterson RA, Reiss S. Anxiety sensitivity index revised test manual. Worthington (Ohio)7 IDS Publishing; 1993. [2] Reiss S, Peterson RA, Gursky DM, McNally RJ. Anxiety sensitivity, anxiety frequency and the prediction of fearfulness. Behav Res Ther 1986;24:1 - 8.
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[26] Plehn K, Peterson RA. Anxiety sensitivity as a predictor of the development of panic symptoms, panic attacks, and panic disorder: a prospective study. J Anxiety Disord 2002;16:455 - 74. [27] Mqller J, Alpers GW, Reim N. Dissociation of rated emotional valence and Stroop interference in observer-rated alexithymia. J Psychosom Res [in press]. [28] De Gucht V, Heisser W. Alexithymia and somatisation. A quantitative review of the literature. J Psychosom Res 2003;54:425 - 34.