Cognitive Therapy and Research, Vol. 14, No. 1, 1990, pp. 37-46

Imagery-Induced Arousal in Individuals

with Panic Disorder

Patti Lou Watkins, 1 George A. Cium, Janet W. Borden, Susan Broyles, and John Hayes

Virginia Polytechnic Institute and State University

Investigators have debated whether imagery can effectively induce arousal in persons suffering from anxiety disorders. Past research suggests that im- aginal exposure to feared stimuli can successfully induce arousal among simple and social phobics. However, owing to the greater complexity o f precipitat- ing stimuli associated with panic attacks (PAs), persons with disorder (PD) have been thought to be relatively unresponsive to imaginal exposure. This study evaluated somatic and subjective arousal in individuals with PD, us- ing relaxation, neutral, stress, and panic imagery. Unlike previous investi- gations, this study incorporated cognitive propositions within the imaginal scenes. As predicted, subjects exhibited significant elevations in heart rate and self-reported distress only in response to stress and panic imagery. Ex- plicit incorporation o f meaning elements (e.g., catastrophic attributions regarding the source of PA symptoms) in the imaginal reconstructions seemed integral to the success of the experimental manipulation. Discussion addresses both theoretical and clinical significance o f these findings.

KEY WORDS: panic disorder; imaginal exposure; arousal induction; attributions.

Exposure-based therapies, particularly when conducted in vivo, have a his- tory of success in treating agoraphobia (Chambless & Goldstein, 1982). However, in the case of panic disorder (PD) where panic attacks (PAs) have not yet been associated with readily identifiable external settings, in vivo ex- posure may be difficult to employ. For instance, Norton, Dorward, and Cox (1986) found that PAs often occur within the broad context of interpersonal

~Address all correspondence to Dr. Patti Lou Watkins, Department of Psychology, Washington State University, Pullman, Washington 99164-4820.

37

0147-5916/90/0200-0037506.00/0 @ 1990 Plenum Publishing Corporation

38 Watkins et al.

conflict and loss or separation from significant others. Such stimuli seem particularly difficult to recreate in vivo. In these cases, imaginal exposure may offer a viable alternative. Some dispute currently exists regarding the efficacy of imaginal techniques for inducing arousal in persons suffering from anxiety disorders. The present investigation addressed the issue of whether imagery is a successful means of inducing arousal in persons with PD or agoraphobia.

Lang (1979) has provided a theoretical basis for expecting that affec- tive states can be recreated via imagery. He contends that physiological and behavioral responses, situational cues, and meanings associated with these are stored together as memory propositions to form an interrelated network of associations. Thus, affective states may be elicited depending on the num- ber and salience of propositions made available to the individual. Therefore, just thinking about information associated with anxiety should produce phys- iological fear symptoms analogous to the active affective state.

Lang, Levin, Miller, and Kozak (1983) found that simple and social phobic college students, pretrained to attend to physiological arousal con- tent in imagery, displayed significant heart rate changes that were analogous to changes displayed by in vivo exposure subjects. Subjects pretrained to at- tend to external stimulus content in imagery, however, failed to demonstrate significant somatic changes l This study underscores the importance of phys- iological response cues versus situational cues in eliciting anxiety. Among clinical outpatients, McNeil, Melamed, Cuthbert, and Lang (1983) found that simple phobics displayed significant changes in skin conductance and heart rate from baseline to imaginal scene presentation. The researchers found less differentiation, however, in agoraphobics' responding. Levin, Cook, and Lang (1982) found physiological changes during imagery comparable to changes produced by in vivo exposure in a clinic sample of phobics. Again, results were least pronounced for agoraphobics. Cook, Melamed, Cuthbert, McNeil, and Lang (1988) found significant skin conductance and heart rate changes during stressful imagery. Here, individuals with simple phobia achieved the greatest level of physiological arousal as compared with those with social phobia and agoraphobia. Average heart rate changes from base- line to imagery were 5.5, 4, and 3 beats per minute for each group, respec- tively. Imagery ability was a significant factor in determining somatic arousal among subjects with simple and social phobia. However, imagery ability was not related to physiological changes among agoraphobics. Furthermore, phys- iological and self-reported affective arousal were significantly related only among simple phobics.

Cook et al. suggest that the consistent lack of arousal in their agorapho- bic subjects is due to characteristically unclear, unstable fear networks. The stimuli that elicit fear in persons with PAs are, by definition (American Psy-

Imagery-Induced Arousal 39

chiatric Association, 1987), more diffuse than typical precipitating stimuli in other phobias. Furthermore, unlike simple and social phobics, agorapho- bics and persons with PD are more likely to have uncertain, changing in- terpretations about the source of their arousal. Recent models (e.g., Beck, Emery, & Greenberg, 1985; Clark, 1986; Clum & Pickett, 1984) emphasize the role of cognitive interpretations in the development and maintenance of PAs. Owing to the apparent absence of a precipitating stimulus, the unex- plained arousal itself may constitute a very frightening experience for which individuals develop catastrophic explanations. Hibbert (1984) found that many people with PD inaccurately attribute their physiological arousal to some type of personal danger, particularly physical harm.

In sum, prior research has found that provocative imagery can elicit significant increases in arousal among persons with nonclinical and clinical anxiety. Agoraphobics seem least responsive to imaginal presentation, pos- sibly because of the greater complexity of their fear networks. Fluctuating cognitive interpretations regarding the nature of their somatic symptoms seem to contribute to this increased complexity. The present study investigated whether imagery could induce arousal in clinic outpatients with PD and agoraphobia if the complexity of their fear networks was sufficiently elabo- rated. It compared heart rate responses during baseline with responses dur- ing personally relevant relaxation, neutral, stress, and panic imagery scenes to answer this question. The stress and panic imagery conditions resembled the Lang, Kozak, Miller, Levin, and McLean (1980) concepts of stimulus and response imagery in that the stress scenes emphasized external stimulus cues while the panic scenes emphasized internal arousal cues. The imagery induction procedures in this study differed from Lang's procedures in that subjects received specific prompts to imagine their usual cognitive interpre- tations of the situation during both the stress and panic scenes. We hypothe- sized that our subjects' heart rates would be significantly greater during the stress, and particularly during the panic, imagery conditions when compared with baseline, relaxation, and neutral imagery conditions. We hypothesized that subjective feelings of distress would increase significantly during the stress and panic conditions as well. We also investigated whether imagery ability would influence physiological and affective arousal among our subjects.

M E T H O D

Subjects and Setting

We recruited subjects through newspaper advertisements and fliers mailed to university employees encouraging individuals with PD symptoms

40 Watkins et al.

to be evaluated free of cost at the university Anxiety Disorders Clinic. A licensed clinical psychologist or an advanced clinical psychology graduate student interviewed subjects using the Anxiety Disorders Interview Schedule (DiNardo, O'Brien, Barlow, Waddell, & Blanchard, 1983). The interviewer then discussed tentative diagnoses based on this contact with the research team until a consensual diagnosis was reached. As a result of this process, 31 subjects, 8 men and 23 women, received DSM-III (American Psychiatric Association, 1980) diagnoses of PD or Agoraphobia with PAs. We evaluat- ed interrater reliability in diagnosing PD versus other anxiety conditions in a previous study (Borden, Clum, Broyles, & Watkins, 1988) and found a 94% agreement rate.

Mean age of the current sample was 36 (SD = 8.3) years. Mean level of education was 2 (SD = 0.5) years of college. Twenty-one subjects were married and 10 were unmarried. Nineteen subjects reported no medication use for their PAs. Of the remaining subjects, 2 reported using xanax alone, 4 reported using xanax and an antidepressant, 1 reported using an antidepres- sant alone, 4 reported using mild tranquilizers, and 1 reported using beta- blocking medication.

Procedure

In a second interview, we identified idiosyncratic imagery scenes for each subject. Four types of scenes were developed. Relaxation scenes described situations in which subjects felt calm and secure (e.g., lying on a beach). Neutral scenes described situations in which subjects felt neither calm nor anxious (e.g., doing housework). Stress scenes described situations in which subjects had experienced anxiety (e.g., shopping in a supermarket) and emphasized external features of the environment as well as cognitive reac- tions to those situations (e.g., "You begin to feel trapped, fearing that you might pass out here right in front of everybody"). Panic scenes described the same features as the stress scenes as well as subjects' physiological reac- tions in the external settings (e.g., "You can feel your heart pounding right out of your chest!") and their misattributions about these sensations (e.g., "You think you're going to have a heart attack!"). We then constructed au- diotapes describing these scenes to serve as experimental stimuli.

We instructed subjects to refrain from taking any medication on the day of the arousal assessment session. Prior to exposure to experimental stimuli, subjects completed the revised Betts Questionnaire of Mental Im- agery (Sheehan, 1967). We categorized subjects as having good (n = 16) or poor (n = 15) imagery ability on the basis of a median split. The median score for the sample was 84. The good and poor imagery groups had mean

Imagery-lnduced Arousal 41

scores of 60 and 108, respectively. We then acclimated each subject to the arousal assessment surroundings for 3 minutes (i.e., the baseline period). Next, we presented the audiotape of subjects' idiosyncratic scenes. For each subject, the tape began with the relaxation scene followed by the neutral, stress, and panic scenes. After the description of each scene, the tape instruct- ed subjects to visualize it for a 1-minute period. At the end of this period, the tape instructed subjects to stop and "just relax." Thirty seconds elapsed before the tape automatically began to describe the next scene. After all four scenes were played, we rewound the tape and replayed it another time, con- stituting the second trial.

We obtained the following measures in response to each scene: (a) heart rate (HR) in beats per minute (BPM) during the 60-second visualization period and (b) a subjective units of distress (SUDS) rating of anxiety on an ascend- ing 1-to-10 scale. Subjects provided the latter measurement during the 30-second interval from the end of one visualization to the beginning of the next scene's presentation. We obtained HR and SUDS measures during the baseline period as well. Two subjects reported that they had misunderstood the instructions in providing SUDS scores and had reversed the scale when reporting their ratings. We eliminated these two subjects from the SUDS data analysis.

In measuring HR, we used two different methods to ensure that BPM were calculated over a 60-second interval. The experimenter in the arousal assessment session used a hand-held stopwatch to determine when a minute had elapsed. Also, each subject's audiotape had been recorded with 60-second intervals between the last word of the instruction to visualize and the first word of the instruction to stop visualizing. These instructions thus served as a cue to begin and end the HR assessment. We assessed HR using a Pulse Meter model PU-102 (manufactured by Thought Technology Ltd), which was attached to the index finger of the subject's dominant hand. A test of the reliability of this method on a separate sample of undergraduate students indicated a high level (98%) of agreement.

RESULTS

Heart Rate Data

We used a 2(trials) x 5(four imaginal scenes plus baseline) design to investigate HR responding for the entire sample. A MANOVA determined whether trials or scenes or an interaction of the two affected this variable. This procedure revealed a significant main effect for trial (F(1, 30) = 7.71, p < .01). Specifically, HR values were higher during the initial presentation

4 2 W a t k i n s e t al.

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Fig. 1. Mean heart rate by experimental condition for Trials One and Two.

of scenes. The analysis also revealed a significant main effect for scenes (F(4, 27) = 5.72, p < .01). Univariate comparisons were accomplished by com- paring the relaxation scene HR with baseline HR. We then compared the neutral scene HR with the average HR of the baseline period and the relaxa- tion scene. Next, we compared the stress scene HR with the average HR from baseline and the relaxation and neutral scenes. Finally, we compared the pan- ic scene HR with the average HR from all four previous observation peri- ods. Using this relatively conservative procedure, both the stress (F(1, 30) = 20.0, p < .001) and panic (F(1, 30) = 14.6, p < .001) scenes were sig- nificantly different from the aggregate mean for the preceding scenes. The average HR (over the two sets of trials) for the stress scene was 4.4 BPM greater than the average HR during baseline. The average HR during the panic scene was 5.8 BPM higher than the average HR during baseline. The analysis did not reveal a significant interaction between trials and type of scene. Figure 1 illustrates the pattern of HR change for each of the two tri- als. In Trial One, mean HR values and standard deviations were 79.6 (12.3), 79.7 (13.2), 80.3 (11.5), 84.7 (12.8), and 85.0 (13.0) BPM for baseline, relax- ation, neutral, stress, and panic conditions, respectively. The corresponding values for Trial Two were 78.3 (10.7), 78.2 (11.0), 78.2 (11.4), 81.5 (11.9), and 83.4 (12.5) BPM.

In order to test for a significant relationship between imagery ability and HR changes, we used a 2(trials) × 5(scenes) × 2(imagery ability) de- sign. A MANOVA determined whether imagery ability itself affected HR and whether imagery ability interacted with trials and /o r scenes to produce

Imagery-Induced Arousal 43

8r Trial One Trial Two r-I Baseline t~t'u [ ] Relaxation ,~ ~ [ ] N~ol -- ~ [ ] Stress

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Fig. 2. Mean SUDS rating by experimental for Trials One and Two.

such changes. This analysis revealed no significant main or interaction ef- fects with imagery ability.

SUDS Data

We used a 2(trials) × 5(scenes) design to evaluate SUDS reports for the entire sample. A MANOVA determined whether trials or scenes or an interaction of the two affected self-reported anxiety. Significant main effects were apparent for trial (F(1,28) = 4.5, p < .05), and scene (F(4, 25) = 22.2, p < .001). As was the case with HR, SUDS responding was significantly higher on the first trial. Again, both the stress scene (F(1, 28) = 45.8, p < .001), and the panic scene (F(1, 28) = 42.2, p < .001) generated signifi- cantly more arousal than the other three scenes. The average rating during the stress scene was 2.8 SUDS higher than the average rating during base- line. The average rating during the panic scene was 3.5 SUDS higher than the average rating during baseline. The scene by trial interaction was, as be- fore, nonsignificant. Figure 2 illustrates the pattern of SUDS change for each of the two trials. In Trial One, mean SUDS values and standard deviations were 3.3 (1.6), 2.9 (1.8), 3.0 (1.8), 6.1 (2.6), and 6.8 (2.5), respectively. Cor- responding values for Trial Two were 2.9 (1.8), 2.7 (2.0), 3.1 (1.7), 5.6 (2.5), and 6.4 (2.6).

We used a 2 (trials) × 5(scenes) × 2(imagery ability) design to test for a significant relationship between imagery ability and SUDS reports. A MANOVA determined whether imagery ability alone affected anxiety level and whether imagery ability interacted with trials and /or scenes to produce such changes. This analysis revealed no significant main or interaction ef- fects for imagery ability.

44 Watkins et al.

DISCUSSION

In this study, clinic outpatients with diagnoses of PD or agoraphobia with PAs experienced significant HR elevations upon imaginal presentation of personally relevant stimuli associated with their PAs. Both stress and panic imagery conditions successfully induced these changes. Significant in- creases in HR were not apparent in response to either the relaxation or the neutral imagery condition. Subjective distress findings paralleled the HR find- ings. Imagery ability was noninfluential in determining subjects' level of phys- iological or subjective arousal.

The HR elevations among the current group of subjects differ from previously reported findings. Lang and colleagues have consistently found minimal increases in physiological arousal among agoraphobic subjects in response to imaginal fear stimuli. The fear networks of persons with PD (and agoraphobia) may be more diffuse and less stable than those of other phobic groups. However, this greater complexity apparently does not preclude trans- formation into an effective imaginal format if the propositions most integral in priming physiological reactivity are sufficiently elaborated. The imaginal fear stimuli in this study included cognitive elements in addition to the ex- ternal setting and physiological response elements featured in Lang's studies. Incorporation of cognitive propositions in the stress and panic scenes may explain the discrepancy between these and earlier findings. This conclusion is somewhat tentative since our study did not include a comparison group of subjects whose imaginal scenes were without prompts to recall cognitive aspects of their panic experience. However, other recent studies provide sup- port for this contention. Foa (1988) found empirical support for the impor- tance of meaning elements in.the onset of PD (i.e., beliefs that somatic symptoms will persist indefinitely and inaccurate beliefs about the cause of these symptoms). She also observed significant elevations in HR and subjec- tive anxiety in response to imaginal fear scenes among persons with PD.

In the Cook et al. (1988) study, imagery ability was significantly relat- ed to physiological arousal in response to phobic fear scenes among simple and social phobics, but not among agoraphobics. However, imagery ability was significantly related to arousal in all three groups when presented with a dental fear script. Cook et al. explained these results in terms of the rela- tive noncohesiveness of agoraphobic fear networks. In this study as well, imagery ability was unrelated to arousal among subjects with PD. However, in this case, cognitive propositions were included in subjects' phobic scenes to reduce the ambiguity associated with these more complex fear networks. Nevertheless, imagery ability was still noninfluential in arousal induction. In explanation, "imagining" cognitive propositions may be qualitatively differ- ent from imagining external setting and internal response propositions. That

Imagery-Induced Arousal 45

is, understanding the meaning of an event may be a separate process from visualizing the circumstances surrounding the event. The Betts Questionnaire of Mental Imagery is designed to tap the latter process. Perhaps elucidating the meaning of imagined events transcends the ability to picture them.

The theoretical significance of the current findings is clear. The HR elevations within the panic imagery condition were of similiar magnitude to those observed among simple phobic by Lang's research group (e.g., Cook et al., 1988), thus indicating that sufficiently elaborated imaginal stimuli are capable of inducing both somatic and subjective arousal in persons with PD. These findings may have clinical significance as well in light of evaluations of alternative means of arousal induction. Margraf, Ehlers, and Roth (1986) reviewed the literature on sodium lactate infusion, finding that only 56% of subjects with a history of panic experienced attacks in response to this intervention. Perhaps more important, Margraf et al. (p. 42) contend that the arousal generated by sodium lactate is characterized by "cold emotion." While subjects experienced physiological arousal, they failed to experience the catastrophic attributions associated with naturally occuring PAs. Margraf et al. suggest that these subjects attributed their arousal to the experimental procedures rather than inexplicable, frightening events. Similarly, when Rapee (1986) questioned subjects in his study about their inability to panic with hyperventilation, he found that many attributed the somatic sensations ex- perienced to the experimental procedures rather than to catastrophic events. Despite these reports, techniques such as sodium lactate injections and hyper- ventilation should not be dismissed as potential means of inducing both so- matic and subjective arousal. If such procedures were accompanied by a convincing clinical rationale, subjective fear reports might have been more closely related to physiological arousal levels. This, however, remains an em- pirical question.

In addition to their uncertain ability to induce arousal, procedures such as sodium lactate infusion are relatively costly, intrusive, and/or difficult to implement. From a therapeutic standpoint, such techniques might be difficult for clinicians to employ or for clients to employ on their own in naturalistic settings. Given these shortcomings, along with the arousal- inducing efficacy of imagery in the current study, researchers might be well advised to explore the utility of imagery in the design of exposure-based ther- apies for PD. The HR elevations observed here, on the average, did not reach levels associated with naturally occurring PAs. However, we employed a rela- tively passive induction procedure compared with what a clinican might em- ploy within a therapeutic context. During therapy, a clinician would interact with the client, exploring the possibility of cognitive avoidance during ex-

46 Watkins et al.

posure and extracting additional cues for anxiety arousal during the course of treatment. Thus, the current findings suggest that imaginal exposure proce- dures have potential utility for clinicans treating individuals with PD and agoraphobia.

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