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ORIGINAL ARTICLES |
From the Department of Psychology, State University of New York at Stony Brook, Stony Brook, NY.
Address reprint requests to: Jennifer Mailloux, The John B. Pierce Laboratory, 290 Congress Ave., New Haven, CT 06519. Email: jmailloux{at}jbpierce.org
| ABSTRACT |
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METHODS: The relationship between Somatosensory Amplification Scale (SSAS) scores and objective measures of the ability to detect bodily (ie, heartbeat) sensations derived from the Method of Constant Stimuli procedure was assessed. Although somatosensory amplification characterizes hypochondriacs, the relationship between somatosensory amplification and sensitivity to bodily sensations was examined in nonhypochondriacal, nonpatient participants in an effort to dissociate somatosensory amplification from other variables associated with hypochondriasis and/or patient status.
RESULTS: Heartbeat detectors were found to exhibit significantly lower SSAS scores than nondetectors.
CONCLUSION: This finding suggests that somatosensory amplification is not due to heightened sensitivity to bodily sensations.
Key Words: somatosensory amplification heartbeat detection hypochondriasis
Abbreviations: ANOVA = analysis of variance;; ECG = electrocardiogram;; MCS = Method of Constant Stimuli;; SSAS = Somatosensory Amplification Scale.
| INTRODUCTION |
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Somatosensory amplification has been implicated as a pathogenic mechanism in hypochondriasis (4). The SSAS has been administered to hypochondriacal and nonhypochondriacal individuals in several studies (3, 510). In these studies, it was found that hypochondriacal individuals scored significantly higher on the SSAS than nonhypochondriacal individuals. It should be noted, however, that a couple of studies have shown that SSAS scores of hypochondriacal and nonhypochondriacal individuals did not differ (11, 12).
Also, it has been argued that hypochondriasis may be characterized by heightened physiological sensitivity to bodily sensations (4, 13, 14). Therefore, hypochondriacs, who amplify bodily sensations, may do so because they are better able to detect bodily sensations than individuals who do not amplify bodily sensations.
Barsky et al. (5) examined whether individuals who amplify bodily sensations are better able to detect bodily sensations. Somatosensory amplification was measured using the SSAS, and the ability to detect bodily sensations, in particular heartbeat sensations, was measured using the Brener-Kluvitse procedure (15) in medical outpatients meeting DSM-III-R criteria for hypochondriasis and nonhypochondriacal medical outpatients. It seems sensible to have assessed the relationship between somatosensory amplification and heartbeat detection ability because hypochondriacs commonly report cardiac symptoms (16, 17).
Barsky et al. (5) found that hypochondriacs scored higher on the SSAS but did not exhibit greater heartbeat detection ability than nonhypochondriacal medical outpatients. Actually, fewer hypochondriacs detected heartbeat sensations than nonhypochondriacal medical outpatients, although this difference did not reach statistical significance. Apparently, hypochondriacs are not characterized by heightened physiological sensitivity to bodily sensations. Therefore, heightened physiological sensitivity cannot account for their tendency to amplify bodily sensations.
The present experiment was designed to investigate further the relationship between somatosensory amplification and heartbeat detection ability. As in Barsky et al.s study (5), participants completed the SSAS and performed a heartbeat detection procedure. However, the present experiment differed from Barsky et al.s experiment in two ways. First, the MCS procedure for assessing heartbeat detection (18) was used instead of the Brener-Kluvitse (15) procedure because the MCS is easier to implement and perform and because its reliability and validity have been thoroughly demonstrated (1822).
Second, nonhypochondriacal, nonpatient participants were used in the present experiment. Investigating the relationship between somatosensory amplification and heartbeat detection ability in nonhypo-chondriacal nonpatients dissociates somatosensory amplification from hypochondriasis as well as variables associated with hypochondriasis and/or patient status. This dissociation allows for a clearer examination of the relationship between somatosensory amplification and heartbeat detection ability. Examining this relationship in nonhypochondriacal nonpatients may elucidate the underlying mechanisms of "normal" somatosensory amplification. In turn, whether the underlying mechanisms of "normal" and "abnormal" somatosensory amplification differ may be determined.
In the present experiment, it was hypothesized that individuals who detect heartbeat sensations will score lower on the SSAS than individuals who do not detect heartbeat sensations. Presumably, individuals who detect heartbeat sensations have become familiar with the sensations produced by the normal physiological functioning of their hearts over time and, therefore, their reports of cardiac sensations are accurate. Conversely, individuals who do not detect heartbeat sensations are not familiar with the sensations produced by the normal physiological functioning of their hearts and, therefore, their reports of cardiac sensations are inaccurate. Perhaps hypochondriacs amplify bodily sensations because they are less sensitive rather than more sensitive to bodily sensations. This would be consistent with Barsky et al.s (5) finding that fewer hypochondriacs, who scored higher on the SSAS than nonhypochondriacal medical patients, detected heartbeat sensations.
| METHODS |
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Apparatus
The SSAS was used to measure somatosensory amplification. The test-retest reliability of the 10-item SSAS and its internal consistency have been demonstrated (3, 23). In the present experiment, the internal consistency of the SSAS was 0.71 (Cronbachs
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During both the familiarization task and the heartbeat detection task of the MCS procedure, participants were seated in a light- and sound-attenuated chamber. The participants ECG was recorded using limb electrodes in the standard lead II configuration. Visual stimuli (light flashes presented for 10 ms) were presented during the familiarization task by means of a light-emitting diode (approximately 4 mm in diameter) situated approximately 2 m in front of the participant at eye level. Auditory stimuli (1000-Hz tones presented for 10 ms at 75 dB) were presented during the familiarization task and the heartbeat detection task by means of a piezo oscillator situated approximately 2 m in front of the participant at ear level. A computer was programmed to detect the R wave of the ECG and to present visual and auditory stimuli.
Participants held a response box housing two response buttons. The button on the left was pressed to register a judgment that the tones presented at the prevailing interval were not simultaneous with light flashes (familiarization task) or heartbeat sensations (heartbeat detection task). The button on the right was pressed to register a judgment that the stimuli were simultaneous. The computer was also programmed to register participants responses.
Procedure
Participants competed the experiment in a single 1-hour session, during which they completed the SSAS and the familiarization and heartbeat detection tasks of the MCS procedure, in that order.
Somatosensory Amplification Scale.
Participants were asked to rate, using a 5-point ordinal response format, the degree to which the 10 statements are "characteristic of you, in general" or "not characteristic of you, in general."
Familiarization Task.
During this 30-trial task, participants judged the simultaneity of light flashes and tones that were presented at stimulus onset asynchronies of 0, 100, 200, 300, 400, or 500 ms. On each trial, participants were presented with five pairs of stimuli at the same stimulus onset asynchrony, which was selected pseudorandomly with the only constraint being that each stimulus onset asynchrony occurred an equal number of times (five) during the task. Participants received the following instructions: "After all five pairs of light flashes and tones have been presented, press the button on the left to indicate that the light flashes and tones were simultaneous or press the button on the right to indicate that the light flashes and tones were not simultaneous." The familiarization task was included to acquaint participants with the procedural demands of the heartbeat detection task.
Heartbeat Detection Task.
On each trial of this 120-trial task, participants were presented with five tones at one of six time delays (0, 100, 200, 300, 400, or 500 ms) following the R wave of the ECG. The R-wave-to-tone delay presented on each trial was selected pseudorandomly with the only constraint being that each delay occurred an equal number of times (20) during the task. Participants were asked to concentrate and attempt to sense the beating of their heart and to judge whether they felt the tones were simultaneous with their heartbeat sensations or not. Specifically, participants received the following instructions: "After all five tones have been presented, press the button on the left to indicate that the tones and heartbeat sensations were simultaneous or press the button on the right to indicate that the tones and heartbeat sensations were not simultaneous." Participants were also informed that direct palpation of the pulse was not allowed.
During either the familiarization task or the heartbeat detection task, if a response button was pressed prematurely (before all five light flash and tone pairs or before all five tones were presented), an aversive tone sounded and the trial was repeated. Otherwise, the next trial began after a 5-second intertrial interval.
The MCS procedure is easier to implement and perform than the Brener-Kluvitse procedure (18). The primary difference between the Brener-Kluvitse and MCS procedures is that in the Brener-Kluvitse procedure, participants examine each of the six R-wave-to-tone delays for as long and as often as they like before selecting the one that they believe yields tones that are simultaneous with their heartbeat sensations. It takes approximately 1 hour for participants to make 30 judgments using this procedure. Using the MCS procedure, it takes approximately 1 hour for participants to make 120 judgments. Brener et al. (18) also showed that the MCS procedure yields indices of heartbeat detection ability that are as reliable as those provided by the Brener-Kluvitse procedure. The validity of the MCS procedure was evidenced by the observation that approximately 79% of individuals classified as heartbeat detectors using the MCS procedure were also classified as heartbeat detectors using the Brener-Kluvitse procedure.
Dependent Measures and Data Analysis
Each participants ratings (from 1 to 5) of each of the 10 items of the SSAS were averaged to obtain a somatosensory amplification score. On the basis of their performance on the heartbeat detection task, participants were classified as heartbeat detectors if their distribution of simultaneity judgments differed significantly from chance according to chi-square analysis. This
2 analysis was calculated using a 2 x 6 Judgments (simultaneous or nonsimultaneous) by Intervals (0, 100, 200, 300, 400, and 500 ms) contingency table. A significant deviation from chance indicated that the participant could detect heartbeat sensations (18). ANOVAs were used to determine whether SSAS scores and ratings of each item of the SSAS differed as a function of heartbeat detection ability, and
2 was computed to determine whether heartbeat detection ability differed as a function of gender. An
level of 0.05 was adopted for all analyses.
| RESULTS |
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The proportion of male heartbeat detectors (N = 9) relative to male nondetectors (N = 17) differed significantly from the proportion of female heartbeat detectors (N = 4) relative to female nondetectors (N = 30) (
2(1,60) = 4.53, p < .05). This indicates that the males in this sample were better able to detect the beating of their hearts than the females in this sample. A nonsignificant main effect of Gender in the MCS Performance by Gender ANOVA on SSAS scores indicated that the somatosensory amplification scores of males (N = 26) and females (N = 34) did not differ (F(1,56) = 2.62, p > .05).
| DISCUSSION |
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Although this interpretation of the inverse relationship found in the present experiment between somatosensory amplification and heartbeat detection ability implies that insensitivity to heartbeat sensations causes somatosensory amplification, such a causal relationship cannot be inferred from this study because of the quasi-experimental nature of the design. Furthermore, the present experiment assessed sensitivity to one type of bodily sensation, heartbeat sensations. It may be that although individuals do not detect heartbeat sensations, they do detect other types of bodily sensations, and somatosensory amplification may reflect sensitivity to these other bodily sensations. Future studies might address whether this is true.
Nevertheless, the lack of a positive association between somatosensory amplification and heartbeat detection ability is consistent with studies that have compared hypochondriacal and nonhypochondriacal individuals, the former distinguished from the latter by higher somatosensory amplification scores (1, 3, 5, 6, 810), and found no differences in auditory sensitivity (25), tactile sensitivity (9), heat pain thresholds (26, 27), heartbeat tracking (28), and heartbeat detection (5). These findings, to which the results of the present experiment can be added, indicate that heightened physiological sensitivity does not account for the amplification of bodily sensations. A few studies have reported that hypochondriacs have greater visual sensitivity (25), greater heart rate awareness (29), and lower pain tolerance (11) than nonhypochondriacal individuals, suggesting that heightened physiological sensitivity may account for the amplification of bodily sensations. The sources of the disparity between these studies and the others referred to above are not immediately obvious, but the weight of evidence decisively favors the conclusion supported by the present experiment.
Rather than resulting from heightened physiological sensitivity, somatosensory amplification may be the result of a cognitive bias toward the misinterpretation of bodily sensations as indicative of disease. Several studies found that hypochondriacal individuals were more likely than nonhypochondriacal individuals to misinterpret normal bodily sensations as indicative of disease (3034). A treatment has been developed based on a model of hypochondriasis as a disorder of perception and cognition resulting from somatosensory amplification (35). This treatment focuses on teaching hypochondriacs to attenuate sensory input, because it has been proposed that hypochondriacs are characterized by heightened physiological sensitivity, and to correct attributional errors, because it has been proposed that hypochondriacs misinterpret normal bodily sensations as indicative of disease. In light of the findings of the present experiment, which suggest that heightened physiological sensitivity does not account for the amplification of bodily sensations, teaching hypochondriacs to attenuate sensory input does not seem to be an effective therapeutic component, at least theoretically. Perhaps the efficacy of this particular treatment (3638) is better attributed to the component that focuses on correcting attributional errors. Future research might address whether this is true.
Consistent with previous research (3, 23, 39), the present experiment found no relationship between gender and somatosensory amplification. However, heartbeat detection ability was related to gender. More male than female heartbeat detectors were identified. Some studies have found gender differences favoring males in heartbeat detection ability (40), whereas other studies have not found gender differences in heartbeat detection ability (18, 21). Although further investigation of gender differences in heartbeat detection ability may be warranted, it should be noted that this is the first occasion on which a gender difference has been found in the authors laboratory.
The finding that somatosensory amplification and heartbeat detection ability are not positively related does not diminish the usefulness of the SSAS as a measure of somatosensory amplification. However, it indicates that a better understanding of the construct of somatosensory amplification must be reached. Apparently, somatosensory amplification does not reflect heightened sensitivity to bodily sensations, at least not in the physiological sense.
Received for publication December 7, 2000.
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This article has been cited by other articles:
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J. Tracy, N. Goyal, A. Flanders, R. Weening, J. Laskas, P. Natale, and B. Waldron Functional Magnetic Resonance Imaging Analysis of Attention to One's Heartbeat Psychosom Med, November 1, 2007; 69(9): 952 - 960. [Abstract] [Full Text] [PDF] |
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