A test of the cognitive model of panic: Primed lexical decision in panic disorder

Journal

of Anxiety

Disorders,

Vol. 11, No. 6, pp. 557-571,

1997

Copyright 0 1997 Elsevier Science Ltd Printed in the USA. All rights reserved

Pergamon

0887.618397

$17.00

+ .OO

PII SO887-6185(97)00029-7

RESEARCH

PAPERS

A Test of the Cognitive Model of Panic: Primed lexical Decision in Panic Disorder CAROLYN

A.

SCHNIERING, Department

B.A.

(HoNs),

of Psychology,

AND Macquarie

RONALD

M.

RAPEE,

PH.D.

University

Abstract - The aim of the present study was to investigate whether individuals with panic disorder are characterised by an enhanced tendency to associate particular somatic sensations with threatening outcomes, compared with nonclinical controls. In order to test this prediction, a modified lexical decision task was employed. Panic disorder subjects and nonclinical control subjects made lexical decisions to neutral word pairs and threatening word pairs. Threatening word pairs consisted of combinations of somatic sensations and catastrophic outcomes (e.g., breathless-su$ocate), which have been shown to be of salience to individuals with panic disorder. Semantic priming was found for both neutral and threatening word pairs, but was demonstrated equally by panic disorder subjects and nonclinical controls. The results did not provide support for cognitive models of panic disorder. 0 1997 Elsevier Science Ltd

Cognitive theories of panic disorder suggest that the central problem in this disorder is a tendency to construe somatic sensations as indicative of extreme physical threat (Beck, Emery, & Greenberg, 1985; Clark, 1986, Rapee, 1993). Specifically, cognitive models propose that the core disturbance in panic disorder involves the misinterpretation of somatic sensations as indicative of an immediately impending physical or mental catastrophe. The misinterpreted somatic symptoms are predominantly autonomic sensations, particularly those associated with the anxiety response, such as palpitations, sweating, and breathlessness. The physical and mental catastrophes typically associated with these Correspondence

Psychology,

and requests for reprints should be sent to Ronald M. Rapee, Department of Macquarie University, Sydney, NSW, 2109, Australia; E-mail: [email protected]&.aq. 557

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symptoms include heart attacks, fainting, dying, suffocating, going crazy, and losing control. Most importantly, it is usually predicted that specific sensations are associatedwith related catastrophes.For example, palpitations might be associatedwith the belief “I am having a heart attack.” Several researchers have argued that as panic attacks are repeatedly experienced, the association between somatic sensationsand threat becomesmore automatic (Lang, 1988; Rapee, 1993). Thus the nature of the association between somatic sensationsand catastrophic outcomesis a crucial componentof cognitive modelsof panic disorder that needsto be empirically supported. Surprisingly, to date, researchin this area has been limited. One source of data that has provided some support for the association between specific somatic symptoms and threat has come from correlational studies (Rachman, Levitt, & Lopatka, 1987; Street, Craske, & Barlow, 1989; Warren, Zgourides, & Englert, 1990; Westling & Ost, 1993). However, several studies have revealed relatively few correlations of significance between somatic sensationsand catastrophicbeliefs (e.g., Rachmanet al., 1987), and there is a lack of consistency acrosscorrelational studies(Costello, 1992). Many of the correlations obtained do not appear to be logically linked. Correlational studies have also been criticised as they fail to outline the definition of a “meaningful” relationship, resulting in the designation of particular correlations as meaningful in quite an arbitrary manner (Costello, 1992). Related to this point, it has been suggestedthat it is typically unclear what is being assessed by measuresof somatic sensationsand beliefs, and that thesemeasures may not be assessingdifferent variables (Costello, 1992). It is possible that somatic sensations,such as “nausea” and thoughts such as “I am going to throw up” actually denote the sameexperience, rather than providing support for cognitive models.Most importantly, correlations between bodily sensations and catastrophic beliefs provide no indication of the direction of the relationship. These data do not establish that somatic sensationsevoke catastrophic thoughts, which precipitate panic attacks. Questionnaireshave been developed to assesscognitive biasesin the interpretation of ambiguousscenariosin panic disorder subjects.A typical scenario involving internal ambiguousstimuli might be “You feel discomfort in your chest area. Why?” (McNally & Foa, 1987). Researchhas shown that individuals with panic disorder are more likely than control subjects to interpret scenarioscontaining ambiguous internal stimuli as threatening (Clark et al., 1988; Harvey, Richards, Dziadosz, & Swindell, 1993; McNally & Foa, 1987). Importantly, however, similar biaseshave alsobeen found in people with social phobia, bringing into question the specificity of the phenomenon(e.g., Harvey et al., 1993). Since both correlational studiesand ambiguousquestionnaire studieshave relied on self-report measures,they are subject to the influences of memory biases, and effects of emotional state at time of testing (Dalgleish & Watts,

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1990). Therefore, the accuracy of such data may be equivocal. Self-report measures are also not useful means of assessing rapid and automatic cognitive processes, which cognitive models predict are operative during the panic attack cycle. Clark et al. (1988) employed a modified contextual priming task, which provided a measure of automatic interpretations of somatic sensations in panic disorder. Subjects were presented with sentences that involved somatic sensations, which were complete except for the last word. Having read this sentence frame, they were presented with a single word and asked to read it aloud as quickly as possible. The single target word provided either neutral or negative interpretation of the somatic sensation specified in the sentence frame. For example, the sentence “If I had palpitations I could be...” was followed by either “dying” or “excited.” Compared to controls, panic disorder subjects were found to be significantly quicker at naming threat words that provided negative interpretations of somatic sensations. This study is the only research to date that has provided evidence for a direct link between somatic sensations and threatening outcomes, which differentiates panic disorder subjects from control subjects. Unfortunately, details of the study are currently unavailable. In summary, the research to date does not provide clear or unequivocal support for the link between somatic sensations and threat in people with panic disorder. The studies reviewed have provided little evidence that individuals with panic disorder have any abnormality in the interpretation of somatic sensations, which clearly differentiates them from individuals without panic disorder. Therefore, the purpose of the present study was to test this central prediction of cognitive models of panic. In consideration of the limitations of self-report measures as noted above, an alternative paradigm from the domain of cognitive psychology was employed. Since cognitive models of panic disorder propose that somatic sensations are associated with threat, it follows that this type of information should be linked in semantic networks (Anderson & Bower, 1973). Word concepts pertaining to somatic sensations, such as breathless, would be expected to be directly linked to word concepts concerning related threatening outcomes, such as su$ocate. Given that such concepts are semantically related, it would be expected that associations between somatic sensations and threat exist in control subjects as well as panic disorder subjects, however, according to cognitive models, these associations should be stronger in panic disorder subjects than in control subjects. One paradigm that has been used to investigate semantic networks and strengths of associations is the primed lexical decision task. In lexical decision tasks, subjects are required to decide as quickly as possible whether a visually presented letter string is a common English word or a nonword. Studies have consistently found that the response time to a target letter string is smaller if the prime word presented immediately prior to the target is a semantically related word. rather than an unrelated word (e.g., nurse-butter vs. bread-butter) (Neely, 1977). This phenomenon, known as semantic priming, has been used as a

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means of exposing semantic structures, and the strengths of associations between word concepts. Semantic priming has also been used as a means of assessing automatic and controlled cognitive processes, by manipulating the time delay between presentation of the prime and the target, known as the stimulusonset asynchrony (SOA) (e.g., de Groot, 1984). At short SOA’s (less than 250 msec) automatic processesare said to be dominant, whereas at long SOAs (greater than 700 msec) controlled processes are said to be dominant. The semantic priming paradigm appears to have several characteristics that make it ideal for providing evidence of a strong, direct link between somatic sensations and threat in panic disorder. It has been demonstrated to be a useful means of exposing semantic networks, and providing a measure of the strength of associations between nodes. Strong associations are reflected in smaller reaction times, or greater semantic priming, compared to weaker associations. In addition, manipulation of the SOA in the lexical decision task can allow an estimate of the contribution of both automatic and controlled cognitive processes. Consequently, a semantic priming task was employed in the present study in order to test the fundamental prediction of cognitive models of panic disorder. Subjects were presented with both neutral word pairs (e.g., butter-bread), and threat word pairs (e.g., breathless-sufocate) as well as nomelated word pairs (e.g., table-sufocate). If panic disorder subjects are indeed characterised by stronger associations between somatic sensations and threat, this should be revealed in reduced reaction times to respond to catastrophic target words following a somatic sensation prime, compared with nonclinical controls. Given that many cognitive theorists have argued that these associations may occur automatically, without the individual’s awareness (e.g., Rapee, 1993), the SOA was manipulated in the present study to allow an approximate measure of the influence of both automatic and controlled cognitive processes.

METHOD Subjects

A total of 75 subjects were included in the study, 47 with panic disorder and 28 nonclinical controls. Panic disorder group. Panic disorder subjects were individuals who responded

to an advertisement in the media. Volunteers were included in the study if their main, or interfering problem was panic disorder, with or without agoraphobia, according to the Diagnostic and Statistical Manual of Mental Disorders (DSMIV; American Psychiatric Association, 1994) criteria. Diagnoses were made by postgraduate students trained by the second author in DSM classification. Comorbid disorders were not formally diagnosed. The group consisted of 32 women and 15 men. Approximately 55% (n = 26) of subjects met criteria for

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the diagnosis of panic disorder without agoraphobia, and the remaining 45% (n = 21) of subjects met criteria for panic disorder with agoraphobia. Control group. Control subjects were individuals who responded to advertisements at various telephone counselling agencies and community centres. Volunteers were included in the study if they had never sought help from a mental health practitioner, and if, based on their own judgement, they reported never having experienced unexpected panic attacks. The nonclinical group consisted of 19 women and 9 men. Design

The design was a 2 (Group: Panic Disorder, Control) X 2 (Word Valence: Threat, Neutral) X 2 (Prime Type: Related, Unrelated) X 2 (SOA: 240 msec, 2000 msec) factorial design with repeated measures on Word Valence, Prime Type, and SOA. The dependent variable was the reaction time to decide whether or not a target letter string was a proper English word. Stimulus Materials

and List Construction

Lists contained pairs of prime and target words, both threatening and neutral in nature. Neutral word pairs, such as butter-bread were chosen from standard word association norms (Postman & Keppel, 1970) such that when the primary word served as a stimulus, the target word was given as the associate at least 40% of the time. Threat word pairs such as heartbeat-coronary and breathlesssufocate were constructed based on clinical reports of typical associations between somatic sensations and threatening outcomes in panic disorder subjects (e.g., Westling & Ost, 1993). For threat word pairs the prime always consisted of a somatic sensation (e.g., heartbeat), and the target consisted of a typical associated catastrophic outcome (e.g., coronary). Word pans were either related, such as boy-gir2, or unrelated, such as job-girl. Each target occurred twice, once in a related prime condition, and once in an unrelated prime condition. The prime words in the unrelated condition were chosen from Kucera and Francis (1967) norms so that they were matched on frequency with the prime words for the related prime condition. On half of the trials the prime was followed by a proper English word, and on the remaining trials the prime was followed by a nonword. Nonword targets were created by changing one letter in words drawn from the remaining set in Postman and Keppel (1970), (e.g., bird to jird) as recommended by James (1975). Prime words for the nonword targets were chosen from Kucera and Francis (1967) norms so that they were matched on frequency with prime words for the word targets. Prime words were displayed for 240 msec or 2000 msec before presentation of the target word for which a lexical decision was made. Subjects were given

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two blocks of 80 word pairs (see Appendix), one with a short SOA, and one with a long SOA. The order of word-pairs was randomised within blocks, in order to control for sequence effects. The different sets of word pairs and SOA conditions were completely counterbalanced across subjects. Testing was preceded by two practice blocks of 28 neutral word pairs, chosen from Postman and Keppel(l970) norms. The SOA for the first practice block was always 2000 msec, and for the second practice block was 240 msec. Other Measures Subjects also completed a number of paper and pencil measures. These included: (a) The Anxiety Sensitivity Index (ASI; Reiss, Peterson, Gursky, & McNally, 1986) to assess fear of somatic sensations, (b) The Albany Panic and Phobia Questionnaire (APPQ; Rapee, Craske, & Barlow, 1994), to assess social fears, agoraphobic fears, and interoceptive fears, and (c) The Depression Anxiety Stress Scales (DASS; Lovibond & Lovibond, 1995), to assess symptoms of depression, anxiety, and stress. Procedure Subjects were tested individually in a 2-hour session. An interview was carried out during which clinical subjects were diagnosed according to DSM-IV (APA, 1994) criteria. The interview was followed by a 30-second period of hyperventilation. Subjects were asked to breathe hard and fast for 30 seconds, and a demonstration was given. They were told that such breathing would probably produce some mild somatic sensations, similar to what might be experienced during a panic attack, which would only be temporary, and cease quickly after the breathing was stopped. Panic disorder subjects have been shown to respond to hyperventilation, which produces a range of symptoms typically experienced during panic attacks, with greater anxiety than do nonclinical subjects (e.g., Rapee, Brown, Antony, & Barlow, 1992). Consequently, hyperventilation was intended to maximise the hypothesised difference between the groups, by partially activating threat-related semantic networks in panic disorder subjects. Following hyperventilation, subjects completed the lexical decision task. General instructions describing the procedure of the lexical decision task were read. Subjects were required to be as fast and accurate as possible in deciding if the target letter string consisted of a proper English word or not. The word pairs were presented on a computer screen and a mouse was used for subjects to respond. Following presentation of the prime word, the target letter string appeared and remained exposed until the subject made a lexical decision by pressing one of two keys, marked on the mouse. Each trial began with a fixation point (a cross) at the centre of the screen, and the interstimulus interval was 2 seconds. Each subject was given two practice blocks and two test blocks.

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1

MEAN SCORESON THE QUESTIONNAIRE MEASURES ACROSSPANICDISORDERAND CONTROLSUBJECTS Group Panic Disorder (n = 47) Measures AS1 APPQ Agoraphobia Interoceptive Social DASS Depression Anxiety Stress 4% Sex Ratio (F/M)

Control (n = 22)

M

SD

M

SD

37.06

10.52

8.76

5.90

30.12 17.87 26.75

18.15 15.84 19.27

8.44 6.04

7.63 4.23 9.63

13.35 17.96 22.00 35.64 32115

12.26 10.05 10.11 10.93

12.64 3.44 .80 5.16 41.07 1919

7.40 0.96 5.62 12.49

ASI: Anxiety Sensitivity Index; APPQ: Albany Panic and Phobia Questionnaire: DASS: Depression Anxiety Stress Scales; M = mean; SD = standard deviation.

RESULTS Subject Characteristics The panic disorder and nonclinical groups did not differ significantly in mean age, F(1,73) = 3.90, p = .052, or sex ratio, x2 (1, N = 75) = .OO,p = .983 (seeTable 1). Scores on the questionnaire measures were submitted to one-way analyses of variance (ANOVA). Significant differences between the panic disorder group and the control group were found across all measures (see Table 1). Panic disorder subjects were characterised by higher levels of anxiety sensitivity than controls, F( 1, 69) = 153.77, p < ,001. The APPQ indicated that the individuals with panic disorder reported greater agoraphobic fears, F(1, 69) = 32.36, p < .OOl, interoceptive fears, F(1, 69) = 13.36,~ < .OOl, and social fears, F(1, 69) = 11.75,~ < .Ol, compared with control subjects. Finally, panic disorder subjects demonstrated significantly higher levels of negative affect including depression, F( 1,69) = 13.58, p < .OOOl,anxiety, F(1, 69) = 72.13,~ < .OOOl, and stress,F(1,69) = 59.81,~ < .OOOl, compared with nonclinical controls. Reaction Time Data

Only data for correct responses were included in the analyses for reaction times. All reaction times less than 100 msec or greater than 1500 msec were excluded from the reaction time data and were scored as errors (these occurred on less than 0.5% of the trials). Data from the practice trials were also omitted.

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Reaction time data included in the analysis, were such that each target word was presented to each subject twice, once in the prime related condition (e.g., boy-girl), and once in the prime unrelated condition (e.g., job-girl). In standard lexical decision research this practice is not advisable, given that reaction times may reflect repetition priming effects (Forster & Davis, 1984), as well as semantic priming effects. However, in the present study this approach was necessary due to the limited number of threat word pairs available. Including all reaction time data in the analyses was intended to reduce error variance and increase power. Statistical analysis of repetition effects revealed a significant repetition priming main effect, t(74) = 3.68, p < .OOOl, as subjects were faster to respond to the second presentation of the target word, regardless of word type. However, there was no significant difTerence in the repetition priming observed for panic disorder subjects and control subjects, F(1, 73) = .17, p = .686. Since Group effects were the primary analyses of interest, the significant repetition priming effects appeared to have little impact on the main results of the study. Analyses revealed that the main effect for SOA was significant, F( 1, 67) = 34.16, p < .OOl. Collapsing across all other variables, shorter reaction times were observed in the short SOA condition, than in the long SOA condition. Because of the important theoretical differences between short and long SOAs, separate analyses were carried out for the two SOA conditions. Statistical analysis of the data was carried out by means of a 2 X 2 X 2 (Group X Word Valence X Prime Type) repeated measures ANOVA, with Group as a betweensubjects factor, and Word Valence and Prime Type as within-subject factors. For both the long and short SOA conditions, assumptions of normality and equality of covariance matrices were supported. Long SOA Semantic priming effects were reflected in the difference in reaction times between the prime related condition and the prime unrelated condition. Priming effects for panic disorder subjects and nonclinical control subjects across word types, for the 2000 msec SOA condition, are presented in Table 2. As expected, the main effect for Prime Type was significant, F(l, 73) = 23.81, p < .OOl. Subjects were significantly faster at responding to target letter strings preceded by semantically related prime words (M = 762.49 msec) than unrelated prime words (M = 791.43 msec). The main effect of Word Valence was significant, F( 1, 73) = 71.77, p < .OOl. All subjects displayed slower reaction times to threat words than to neutral words. Main effects for Word Valence and Prime Type were qualified by a significant interaction between Word Valence and Prime Type, F( 1,73) = 4.62, p < .05. Multiple comparisons revealed significant differences between the means for all possible contrasts, including threatrelated and threat-unrelated words, t(74) = 2.07, p < .05, neutral-related and neutral-unrelated words, t(74) = 4.96, p < .OOOl, threat-related and neutralrelated words, t(74) = 7.42, p < .OOl, and threat-unrelated and neutral-unrelated

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TABLE 2 MEAN REACTION TIMES FOR PANIC DISORDER AND CONTROL SUBJECTS FOR THE 2000-MSEC SOACOND~~N Group Panic Disorder Word

Type

Threat Related Unrelated Neutral Related Unrelated

(n = 47)

Control

(n = 22)

M

SD

M

SD

789.92 810.00

164.33 140.76

803.5 1 816.24

121.62 120.76

716.59 763.34

138.07 133.22

739.93 776.12

123.22 124.94

M = mean; SD = standard deviation.

words, t(74) = 5.25, p < .OOl. The difference between related and unrelated word pairs was greater for neutral words than for threat words. The main effect for Group in the long SOA condition was not significant, F(1,73) = .21, p = .650. The main focus of interest was the interaction between Group, Word Valence, and Prime Type, asthis would indicate enhancedpriming effects for threat words in panic disorder subjectsin comparisonwith control subjects.In contrast to the predictions made, the interaction of Group X Word Valence X Prime Type did not reach significance, F(1, 73) = .02, p = 297. There were no significant differences in priming effects between panic disorder subjectsand nonclinical controls, irrespective of Word Valence.

Short SOA Priming effects for panic disorder subjectsand nonclinical control subjects acrossword types, for the 240 msec SOA condition, are presentedin Table 3. The pattern of results obtained for the short SOA condition was very similar to that obtainedfor the long SOA condition. There were significant main effects of Prime Type, F(l, 73) = 37.03, p < .OOl, and Word Valence, F(1, 73) = 41.65, p < .OOl. The main effect for Group in the short SOA condition was not significant, F(1, 73) = .52, p = .475. Contrary to expectations, the interaction of Group X Word Valence X Prime Type was not significant, F(1, 73) = .87, p = .355. As was the case with the long SOA condition, panic disorder subjects did not demonstratesignificantly greater priming compared to nonclinical controls for threat words over neutral words.

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TABLE 3 MEAN REACTIONTIMES FOR PANIC DISORDER ANDCONTROL FOR THE 240~s~~ SOACONDITION

SUBJECTS

Group Panic Disorder Word Type Threat Related Unrelated Neutral Related Unrelated M = mean;

(n = 47)

Control

(n = 22)

M

SD

M

SD

714.21 750.60

151.46 151.70

737.76 781.80

113.27 139.51

662.40 703.66

131.84 142.88

685.46 712.76

119.62 120.36

SD = standard deviation.

DISCUSSION The results of the present study demonstratedsignificant semantic priming effects acrossall subjectsfor both threat and neutral word pairs. Surprisingly, however, no significant group differences were evident. That is, both panic disorder subjects and nonclinical controls demonstrated equivalent priming effects for both threat and neutral words. This occurred irrespective of SOA condition. In brief, the observed semanticpriming effects provided no evidence for a stronger association between somatic sensationsand threat in panic disorder subjectscompared with nonclinical controls. It is important to recognisethat the resultswere not indicative of a complete absence of an association between somatic sensationsand threat in panic disorder, as significant priming effects for threat words in panic disorder subjectswere found. However, contrary to cognitive modelsof panic disorder, the propensity to associatecertain somatic sensationswith impending disaster was not found to be a critical distinguishing factor between panic disorder subjectsand nonclinical controls. Semantic priming effects were demonstratedby both groups of subjects in the study, and were consistentwith previous literature on semanticpriming of lexical decisions (e.g., Neely, 1977). Subjects were quicker to make lexical decisionsfor target letter strings precededby semantically related items, than unrelated items. The strength of the effect was stronger for more common associates(neutral word pairs) than lesscommon associates(threat word pairs) and was found on both slow (controlled) and rapid (automatic) processing conditions. The consistency of the present results with previous research, indicates that the general method in the presentstudy was adequateasa means of exposing both semantic structures, and the relative strengths of the associations between concepts within these structures.

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The sampleof clinical subjectsin the study also appearedto be adequate with respect to diagnosis and samplesize. All clinical subjects met DSM-IV (APA, 1994) criteria for the diagnosisof panic disorder, and their scoresacross questionnairemeasureswere consistent with past research(Lovibond & Lovibond, 1995; McNally & Lorenz, 1987; Rapeeet al., 1994). The samplesize of panic disorder subjectsin the present study (n = 47) was large compared with most experimental studiesof panic disorder where typically 20 to 30 subjects per group are used.This samplesize provided adequatepower (.8) to detect a moderate effect size (y = .57), at (Y = .05, one-tailed (Welkowitz, Ewan, & Cohen, 1976). It is possiblethat having subjectshyperventilate prior to engagingin the task may have minimized differencesbetween groups. This is highly unlikely asthe hyperventilation was included precisely to maximize group differences. Previous researchhas indicated that people with panic disorder respondwith greater fear to hyperventilation than do nonclinical controls and this effect is presumably mediated by associationswith threat (e.g., beliefs by the panic disorder subjectsthat they are passingout, dying, etc.) (Rapee et al., 1992). Therefore, if anything, hyperventilation should have activated the threat schemasfor people with panic disorder to a greater extent than for nonclinical subjects. A more plausible limitation lies in the suggestionthat specific associations between physiological sensationsand threat may often vary from person to person, be few in number, and may change over time (Rapee, 1993). Consequently, it is possible that panic disorder subjects and nonclinical controls showed equivalent priming for threat words, becauseeffects are too idiosyncratic and transient to be revealed by averaging acrossword pairs. If this is the case, this issue cannot be overcome using the present paradigm, or indeed virtually any of the common information processingparadigms.The fact that previous studiesusing information processingparadigmsand averaging across word presentationshave consistently found effects, arguesagainst the importance of this difficulty. The most seriouslimitation of the presentstudy lies in the fact that each time a somatic sensationprime was presented,it was followed by either an unrelated word, or a threat outcome. Hence, the associative strength between sensations and threat for nonclinical controls may have been artificially inflated by the possibility that over the course of the study, they learned to expect threat associatesto follow somaticprimes.This effect may have beenenhancedby the overall context of the study, which was overtly designedto investigate anxiety. Future studies using this paradigm will need to construct stimuli such that somatic sensation primes are followed by either threatening targets (e.g., sweating-panic), or neutral targets (e.g., sweating-exercise), rather than only threatening targets. In the only successfuldemonstrationof this phenomenon, subjects were presentedwith a choice between a threat and neutral outcome (e.g., dying vs. excitement), thereby not allowing expectancy effects that may have occurred in the present study (cf., Clark et al., 1988).

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In contrast to this argument, it has been suggestedthat deliberate response strategies are rarely employed in reaction time paradigms, such as lexical decision, where subjectsare directed to respondas quickly aspossible(Roediger & McDermott, 1993). It hasbeen suggestedthat particularly at short SOA’s there is insufficient time for explicit strategiesto be activated, or for expectancy effects to come into play (de Groot, 1984).Therefore, if expectancy effects were responsiblefor inflating the apparent associative strengths of nonclinical responses,this effect should have been more apparentin the long SOA condition than in the short SOA condition. This was not the case. It appearsthen, that severalpotential methodologicallimitations to the study may still not fully explain the lack of differences found between groups. This leaves findings that are difficult to reconcile with current cognitive models of panic disorder. Taken at face value, the results of the current researchindicate that both clinical and nonclinical subjects associatesomatic sensationswith threatening outcomesand that this occurs to the sameextent in both groups. If this is the case,it may prove necessaryto consider alternative factors that may clearly distinguish individuals with panic disorder from those without panic disorder. For example, the perceived valence, or cost, attached to the feared catastrophic outcome (e.g., Harvey et al., 1993; McNally & Foa, 1987) has frequently been overlooked asa potential crucial factor discriminating individuals with panic disorder from others. For example, when experiencing palpitations, it is possiblethat everyone will consider an equivalent probability that this symptom signals a coronary. However, people with panic disorder may attach a far greater cost to coronaries than other individuals. Another possible factor of importance may be perceptionsof control (Barlow, 1988; Sanderson, Rapee, & Barlow, 1989). According to this view, people with panic disorder may associatethreat with sensationsto the samedegreeas anyone else,but may be more likely to believe that they have no mechanismsby which to modify or control theseoutcomes.Clearly, further investigation is neededto test between these various possibilities.

REFERENCES American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Anderson, J. R., & Bower, G. H. (1973). Haman associative memory. Washington, DC: Winston. Barlow, D. H. (1988). Anxiety and its disorders. New York: Guilford Press. Beck, A. T., Emery, G. D., & Greenberg, R. L. (198.5). Anxiety disorders and phobias: A cognitive perspective. New York: Basic Books. Clark, D. M. (1986). A cognitive approach to panic. Behaviour Research & Therapy, 24.4617470. Clark, D. M., Salkovskis, P. M., Gelder, M., Koehler, C., Martin, M., Anastasides, P., Hackmatm, A., Middleton, H., & Jeavons, A. (1988). Tests of a cognitive theory of panic. In I. Hand & H.U. Wittchen @Is.), Panic and phobias 2 (pp. 149-158). Berlin: Springer-Verlag. Costello, C. G. (1992). Problems in recent tests of two cognitive theories of panic. Behaviour Research and Therapy, 30, 1-5.

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570

C. A. SCHNIERING

AND

R. M.

RAPEE

Westling, B. E.. & Ost, L. G. (1993). Relationship between panic attack symptoms panic disorder patients. Journal ofilrtxie~ Disorders. 7, 18 1-194.

LEXICAL

BLOCK 1. RELATED

UNRELATED

BLOCK 2 RELATED

UNRELATED

WORD

PAIRS

WORD

WORD

PAIRS

PAIRS

WORD

PAIRS

APPENDIX DECISION STIMULI:

WORD

and cognitions

PAIRS

THREAT

NEUTRAL

PAIN - FATAL SWEATING - PANIC BREATHLESS - SUFFOCATE NUMB - DISEASE UNREAL - CRAZY NAUSEA - ILLNESS CONFUSED - INSANE THROBBING - TUMOUR DIZZY - UNCONSCIOUS UNSTEADY - WEAK NAVIGATOR - DEATH ARCTIC - CORONARY MONTH - FEVER SKYSCRAPER - COLLAPSE SHAVING - STROKE CHESS - CHOKE CARDBOARD - FAINT GEM - PARALYSED MOBILE - MAD ROSE - LETHAL

DREAM - SLEEP HUNGRY - FOOD YOU - ME BREAD BUTTER TABLE - CHAIR HARD - SOFT BOY - GIRL GREEN - GRASS FINGERS - HAND SALT - PEPPER TURKEY NAIL CARBON - SELLING EAST - LIGHT LEFT - LOW GRAY - QUEEN TOP - WHITE DUST - CATS TOWN - TALL HOOP - SWEET AS - OFF

PALPITATION - DEATH HEARTBEAT - CORONARY HOT - FEVER UNSTEADY - COLLAPSE TINGLING - STROKE GASP - CHOKE DIZZY - FAINT NUMB - PARALYSED CONFUSED - MAD PAIN - LETHAL KEY - FATAL TEXTBOOKPANIC SANDMAN - SUFFOCATE SCARF - DISEASE ALBUM - CRAZY HANDBAG - ILLNESS WISDOM - INSANE NAPKIN - TUMOUR SAILOR - UNCONSCIOUS

HAMMER - NAIL BUYING - SELLING DARK - LIGHT HIGH - LOW KING - QUEEN BLACK - WHITE DOGS - CATS SHORT - TALL SOUR - SWEET ON-OFF CREDIT - SLEEP CRYSTAL - FOOD ALL - ME WITNESS - BUTTER MODERN - CHAIR PLAN - SOFT JOB - GIRL CHIEF - GRASS FOREST - HAND

in

LEXICAL

DECISION

IN PANIC

THREAT

NEUTRAL

HOUSEKEEPER NONWORD PAIRS Examples of nonword targets SLAVE - JIRD MESSAGE - YATS WITCH - POTH CAPTAIN - DOLD GREED - ZOW MIDNIGHT - FOW CLAWS - PAND SECRET - TIRT FUN - DAST

and primes

571

DISORDER

- WEAK

are given below.

WAVE

- PEPPER