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ORIGINAL ARTICLES |
From the Wake Forest University School of Medicine, Department of Internal Medicine, Section of Gastroenterology, Winston-Salem, North Carolina (M.E.L., K.L.K.); The Pennsylvania State University, Department of Psychology, University Park, Pennsylvania (R.M.S.).
Address correspondence and reprint requests to Max E. Levine, PhD, Department of Internal Medicine, Section of Gastroenterology, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157. E-mail: mlevine{at}wfubmc.edu
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONNOTESREFERENCES |
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Method: Seventy-five participants were assigned to one of three groups. Positive-expectancy group participants were given placebo pills that would allegedly protect them against the development of nausea and motion sickness. Negative-expectancy group participants were given the same pills as nocebos; they were led to believe there was a tendency for them to make nausea somewhat worse. Placebo-control group participants were told the pills were indeed placebos that would have no effect whatsoever.
Results: Subjective symptoms of motion sickness were significantly lower among negative-expectancy group participants than positive-expectancy and placebo-control group participants (p< 0.05). Gastric tachyarrhythmia, the abnormal stomach activity that frequently accompanies nausea, was also significantly lower among negative-expectancy group participants than positive-expectancy and Placebo-Control Group participants during drum rotation (p<.05).
Conclusions: Inducing negative expectations through nocebo administration reduced nausea and gastric dysrhythmia during exposure to provocative motion, whereas positive placebos were ineffective for preventing symptom development. That manipulation of expectation affected gastric physiological responses as well as reports of symptoms, suggests an unspecified psychophysiological mechanism was responsible for the observed group differences. These results also suggest that patients preparing for difficult medical procedures may benefit most from being provided with detailed information about how unpleasant their condition may become.
Key Words: placebo • nausea • gastric tachyarrhythmia • electrogastrography • EGG • motion sickness
Abbreviations: SSMS = subjective symptoms of motion sickness; EGG = electrogastrogram; ANOVA = analysis of variance; FFT = fast-Fourier transform.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONNOTESREFERENCES |
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Placebos and their effects have often been regarded as nuisances to experimental designs employed for the evaluation of medical interventions (3). The administration of placebos, however, represents an ideal paradigm for the study of mind-body interactions. Unfortunately, the placebo effect has not received the attention it deserves in focused experimental research; it has more often been considered a source of nonspecific noise in otherwise informative data. Growing recognition of the significance of placebo effects in therapeutic settings is illustrated by the popularity of study designs that control for the effect of the administration of a treatment independent of the effects of its active ingredient. Such designs represent a considerable step forward in appreciating the extent of a placebo's influence but still do not enhance understanding of how and why placebo effects occur. Recently, attention has been focused on the underlying mechanisms of the placebo response, thanks to a renewed interest in mind-body interactions and behavioral medicine in psychological research.
There are now numerous published demonstrations of the placebo effect as a legitimate subjective phenomenon, and many studies that suggest placebos' effects on reported symptoms are accompanied by measurable physiological changes (eg, 4–6). Though support for the counterargument that placebo effects are due merely to biased perceptions of an unchanged bodily state is now relatively scarce, such claims are still made. For example, Hrobjartsson and Gotzsche (7) suggested placebo effects are artifacts of the natural remission of symptoms of some unpleasant condition and that placebo responses should be attributed to the natural regression of the severity of a disease or illness. Likewise, Ross and Olson (8) emphasized the role of misattribution of naturally, spontaneously occurring, and/or ambiguous changes in condition to the administered placebo as a mediator of the placebo response. Kirsch (9), in contrast, contended that spontaneous remission of symptoms could not account for the placebo effect given studies that control for the natural waxing and waning of symptoms, and still demonstrate a placebo effect.
Another common challenge to the legitimacy of the placebo effect is that the subjective experience of a placebo response is not accompanied by physiological changes (9). Rather, a response bias is said to be the underlying mechanism of an imagined placebo effect. Given the selective attention paid exclusively to signs of the purported effects of the alleged treatment, it is argued, any sensation in conflict with the expected effects of the placebo is simply ignored. The perceptual bias perspective suggests that expectation-induced perceptions of change are based on events that have not actually occurred in the body. In addition, compliance demand resulting from the desire to please the person administering the treatment is thought by skeptics to mediate such effects. According to this perspective, the placebo-treated individual somehow learns the hypothesis of the study and becomes motivated to please the experimenter. These alternatives are contradicted by evidence of involuntary physiological placebo effects. For instance, Wolf (10) noted placebo-induced gastric acid-secretion and contraction. Fields and Levine (11), among others, demonstrated that placebo-induced analgesia is reversed by administration of the opioid-antagonist naloxone, suggesting a legitimate physiological basis for such effects. Kirsch and Weixel (4) demonstrated that patients who reported feeling either more aroused with the administration of placebo stimulants or less aroused with the administration of placebo tranquilizers exhibited corresponding changes in heart rate and blood pressure. This body of evidence is suggested by Kirsch (9) to disprove the notion that placebo effects are artifactual events created by response biases unaccompanied by physiological changes.
Placebo effects are not foreign to studies involving the treatment of gastrointestinal symptoms. Mearin et al. (6) administered placebos to patients with functional dyspepsia, a disorder marked by abdominal pain or discomfort centered in the upper abdomen and/or nausea, bloating, and early satiety following meal ingestion (2). The condition lacks a substantiated structural or biochemical explanation but is often accompanied by disturbed gastric motility. After 8 weeks of placebo treatment, scores on a global symptom index were significantly reduced in 80% of the patients. The reduction in symptoms was accompanied by a return of normal gastric motility. The placebo's effect on subjective symptoms could not, therefore, be attributed solely to a response bias. In a series of studies exploring the use of acustimulation for the management of nausea and gastric dysrhythmia, significant placebo effects were observed (12–14). The authentic treatment was consistently better than a placebo treatment for reducing nausea, indicating a value of acustimulation independent of the placebo effect it produced, but the placebo treatment was also significantly more effective than no treatment. In a comprehensive review of the placebo response, Thompson (15) noted several instances of the placebo effect in gastrointestinal medicine but emphasized that a great deal of additional research is necessary to identify the causal mechanisms involved.
The idea that the placebo response represents a specific biological phenomenon is based on the assumption that mental experience can somehow affect physiology. According to Fields and Price (16), the administration of a placebo alters the interacting neural representations of memory, environmental context, and specific sensory stimuli. This aggregate of neural activity translates into a subjective experience that simultaneously affects physiology. Indeed, cognitive factors like attribution, belief, desire, motivation, and expectation may be potent mediators of the placebo response (17). That placebo effects of greater magnitude are achieved by more believable and technically sophisticated agents seems to support this idea. For instance, placebo injections elicit greater placebo responses than placebo pills, and larger pills are associated with stronger placebo responses than smaller pills; the number of pills taken is also directly related to the magnitude of the placebo response (8). Also, when there is a strong desire for a given treatment to produce a certain effect, as when pain is extraordinarily intense, the placebo effect tends to be augmented.
Response expectancy theory attributes the placebo effect to the forming of expectations that an ingested substance will produce both subjective and physiologic changes in accordance with the supposed effect of that substance (18). Response expectancy is defined as the anticipation of the occurrence of nonvolitional, automatic responses. For instance, if an individual expects a treatment to produce relief from pain, intoxication, vomiting, or any other response that is not under that individual's direct control, the effect is much more likely to take place than if no such expectation exists. Individuals can learn to expect certain outcomes simply by listening to others' descriptions of a treatment to be administered or by observing the behavior of others who supposedly have experience with the treatment (19). Kirsch suggested that the single most influential determinant of the placebo response is one's expectation that some change in bodily state will be achieved through the administration of a placebo treatment.
Internal states such as mild nausea tend to be somewhat ambiguous, particularly during the early stages of their development. This ambiguity may underlie the strong association between response expectancy and involuntary, automatic responses to stimuli (18). A response expectancy may induce a perceptual set that is employed for the interpretation of ambiguous bodily sensations. Once an interpretation has been made that a set of vague physiological sensations is representative of the anticipated condition, an unspecified psychophysiological mechanism is initiated that produces the expected physical symptoms that otherwise may not have developed. For example, if a cancer patient anticipates the development of nausea during chemotherapy, she might first notice only benign sensations. Having the response expectancy of severe nausea, however, she might validate her anticipation by interpreting the sensations as indicative of the beginning stages of a bout of severe nausea. Having drawn that conclusion, a psychophysiological mechanism that represents the intricate interrelationship between mind and body produces the physiological response associated with the anticipated sickness. This still does not explain specifically how response expectancy induces the development of anticipated physiological conditions, but response expectancy theory represents one of the only attempts to explicate the physiological aspects of expectations.
Several studies suggest expectations play a meaningful role in the development of nausea symptoms. Chemotherapy patients exhibit direct relationships between expectations for nausea before their first treatment and nausea that actually develops (20,21). In addition, patients who expect nausea side effects of the treatment report significantly more severe nausea than those who do not. Eden and Zuk (22) conducted a study of naval cadets undergoing training on rough seas that often promote the development of nausea and motion sickness. Some of the cadets were provided with a "verbal placebo" in an attempt to help them avoid the onset of seasickness. They were told that, based on their psychological and physiological profiles, they were unlikely to develop seasickness once they were exposed to the rough water of the open sea. The cadets provided with the placebo manipulation developed significantly less severe seasickness than those who did not.
The power of expectation is evident when one considers the effects of negative expectancies as well as positive ones on subsequent symptoms. A nocebo effect is defined as "a causation of sickness by expectation of sickness and by associated emotional states" (23). Luparello et al. (24) demonstrated that expectations of the effects of a treatment could go in either a positive or negative direction. Asthmatics were given an innocuous saline solution to inhale but were told that the substance contained irritants that might temporarily worsen their condition. Dramatically increased airway resistance and a corresponding perception of increased difficulty with breathing were produced by the manipulation. When the same substance was administered again, but instead described as therapeutic, airway resistance decreased and easy breathing returned. Jewett et al. (25) presented additional evidence that the placebo effect on allergic reactions can operate in the negative direction.
The aim of the present study was to examine the effects of manipulating expectations through placebo and nocebo administration on reports of symptoms and physiologic responses in the context of nausea and motion sickness. Three independent groups of participants received identical placebo pills before exposure to a motion sickness stimulus but were led to believe the pills contained different pharmacological agents. One group received pills described as being effective for the prevention of nausea and motion sickness. Another received pills described as having the potential to facilitate the development of nausea and motion sickness. A control group was not deceived as to the nature of the pills they were taking. It was hypothesized that relative to the control group, a traditional placebo effect would be demonstrated by the first group, and a traditional nocebo effect would be exhibited by the second group. This pattern of group differences was hypothesized to be evidenced by subjective evaluations of the severity of nausea and motion sickness symptoms and by differences in gastric tachyarrhythmia, the abnormal stomach activity that consistently accompanies nausea and is assessed through electrogastrography (EGG).
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METHODS |
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Apparatus
The rotating optokinetic drum employed in the present study was a metal cylindrical chamber 91.5 cm in height and 76.0 cm in diameter (Figure 1). On the inside surface of the drum were alternating black and white vertical stripes; the black stripes were 3.8 cm wide (7° visual angle) and the white stripes were 6.2 cm wide (11°). The light source inside the drum was a 40-W light bulb mounted in a rectangular lamp near the bottom of the drum. Participants sat on a stool inside the drum with their heads positioned approximately in the center of the cylinder. The viewing distance was roughly 35 cm. The drum was rotated at a constant speed of 60°/second (10 rpm) in the clockwise direction (left to right for the viewer). Viewing of the drum's rotation induces the illusion of self-motion. A Sony camera mounted inside the drum was used to ensure that participants kept their eyes open and directed straight ahead at the movement of the drum throughout the experiment. An intercom system allowed for two-way communication between the experimenter and the participant inside the drum to be maintained from an adjacent room.
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Subjective Measures
The Subjective Symptoms of Motion Sickness (SSMS) questionnaire was used to assess the severity of participants' nausea and motion sickness symptoms during exposure to the rotating drum (27). Common symptoms of motion sickness were assessed once by asking participants about them over an intercom system immediately before their exposure to the rotating drum was discontinued. For questions pertaining to the severity of dizziness, headache, warmth, sweating, drowsiness, and salivation, scores of 0, 1, 2, and 3 were assigned for responses of none, slight, moderate, and severe, respectively. For the question pertaining to stomach awareness, scores of 0, 1, 2, 3, and 4 were assigned for responses of none, stomach discomfort (without nausea), slight nausea, moderate nausea, and severe nausea, respectively. SSMS scores were calculated as the total number of points assigned for all of the symptoms in the questionnaire. The range of possible SSMS scores was therefore 0 to 22. Nausea was rated by participants once before and every 2 minutes during exposure to the rotating drum along a scale from 0 to 10, with 0 representing "not at all" and 10 representing "extremely." Mean nausea ratings were taken as an index of the severity of nausea experienced. Finally, the amount of time before participants requested early termination of the drum rotation period (if ever) was taken as another indication of participants' toleration of the drum's stimulation.
EGG
EGGs were recorded throughout the experiment in a manner identical to that described by Levine et al. (28) from three electrodes placed on the surface of the abdomen over the stomach. The electrodes detect signals that reflect gastric myoelectrical activity. The EGG data were analyzed using running spectral analysis software (EZEM, Lake Success, NY). Spectral analyses were performed on the 6 minutes of each baseline and the entire duration of the drum rotation period. The first 4 minutes of each period comprised the first epoch to be analyzed. The last 75% (minutes 2, 3, and 4) of the first epoch was combined with the first new minute (minute 5) to comprise the second epoch, and so on. Therefore, three epochs were analyzed for each baseline period (minutes 1–4, 2–5, and 3–6) and then averaged for each period. As many epochs allowable by the number of minutes of data that were obtained during the drum rotation period were analyzed and averaged for the entire period. The 75% overlap in each epoch provides stable spectral estimates. The epochs were analyzed via fast-Fourier transform (FFT) to obtain spectral estimates for each 240-second epoch. Estimates of the percentage of EGG power within the gastric tachyarrhythmia frequency bandwidth (4.00 to 9.75 cpm) were obtained for each experimental period based on the method of Uijtdehaage et al. (29). Movement artifacts in the EGG were detected by visual inspection of the record as they occurred; minutes containing such artifacts were excluded from the analysis.
Procedure
Participants were informed that the study involved the investigation of two pharmacological agents designed for the prevention of motion sickness symptoms. They were told they would be assigned to one of three experimental groups. Participants in one of the groups would receive a drug that had already been established as being effective for the prevention of motion sickness, although it had never been tested during exposure to this stimulus. Participants in another group would receive a newer anti–motion sickness drug in the process of being developed that was meant to combat specifically the dizziness associated with motion sickness. Members of the third group would receive an inactive placebo that would serve as a comparison for each of the drugs being tested. Before participants were informed of the group to which they were assigned, they were seated in the motionless drum for 6 minutes while their baseline EGG data were recorded.
Following the first baseline, participants were informed of the group to which they had been assigned. Positive-Expectancy Group participants were told they would receive the drug that had allegedly been established as being effective for the prevention of motion sickness. In order to strengthen the effectiveness of the manipulation, participants were also given an informational document that described in detail the nature of the pills they would be taking. Participants were told that the experimenters needed to be able to demonstrate that participants fully understood the nature of the pills before they swallowed them. They were instructed to read carefully and sign the document in order to indicate their understanding of the pharmacological agent they were about to ingest. The document described the pills as being likely to be effective for reducing the severity of nausea and motion sickness symptoms in motion sickness environments like the rotating drum.
Negative-Expectancy Group participants were told they would receive the recently developed drug for the dizziness of motion sickness. They were informed that for some people, the dizziness associated with motion sickness is the most undesirable and problematic symptom, so a drug that reduces that symptom would be a valuable product to make available for these people. They were then warned that although preliminary reports from other laboratories suggested the drug was somewhat effective for reducing dizziness, it tended to make other symptoms of motion sickness more severe. Allegedly, people taking this newer drug were, for some unknown reason, reporting more severe nausea, stomach discomfort, warmth, and other symptoms of motion sickness than people not taking the drug. Negative-Expectancy Group participants were also given an informational document to read carefully and sign in order to indicate their understanding of the nature of the pills they were to ingest.
Placebo-Control Group participants were informed they would be taking the pills that contained no active ingredient. They were told they should not feel they would be any more likely to develop symptoms than participants in the other two groups since the two drugs being tested were not yet known to be effective for reducing symptoms during exposure to this stimulus. They were instructed to read through and sign their own informational document that provided a detailed explanation of the nature and purpose of the pills they would be taking.
All participants were then given 6 oz of cold water and the same two small, green, encapsulated pills. The pills were described as rapidly dissolving capsules that would take effect quickly but that a 10-minute delay would be necessary for the active ingredient to be absorbed into the bloodstream before the experiment could continue. After the 10-minute period had elapsed, participants sat in the motionless drum for another 6 minutes as their EGG data were collected. Following the second baseline, participants were asked to rate their nausea and were told that the drum would begin to rotate within 30 seconds. Participants were then exposed to the rotating drum for 16 minutes, or for less time if early termination was requested.
Before the debriefing at the conclusion of the study, participants took part in a loosely structured interview designed to determine if they were ever suspicious of the true nature of the pills they were ingesting or of any other part of the experiment. Three participants in the Positive-Expectancy Group and three participants in the Negative-Expectancy Group expressed some degree of suspicion, although their responses did not differ significantly from other participants in their groups. Nonetheless, data from these participants were subsequently withdrawn from all between-groups comparisons.
Statistical Analysis
Group means were computed for each subjective variable. Univariate analyses of variance (ANOVAs) were performed with experimental group as the independent variable. ANOVAs were completed in order to detect significant differences between groups in terms of SSMS scores, nausea ratings, and stimulus exposure times. Group means were also computed for percentage EGG power in the gastric tachyarrhythmia frequency range during each of the three experimental periods. Two-factor ANOVAs were performed with group as one independent variable and period as the other in order to detect main and interaction effects on percent gastric tachyarrhythmia. When appropriate, follow-up univariate ANOVAs were performed with group as the independent variable in order to explore further the differences between groups during each period. Tests of null hypotheses resulting in p values of .05 or less were considered statistically significant. Tukey tests were performed to make post hoc pairwise comparisons when appropriate.
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RESULTS |
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A significant effect of experimental group on mean ratings of nausea during exposure to the rotating drum was also observed, F(2,66) = 3.42, p < .05, but in the same unexpected direction. Nausea ratings made by Negative-Expectancy Group participants were significantly lower than ratings made by Placebo-Control Group participants. Nausea ratings made by Positive-Expectancy Group participants were not significantly different from ratings made by Negative-Expectancy or Placebo-Control Group participants (Figure 3).
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Finally, a significant effect of experimental group on the amount of time participants tolerated the drum's stimulation was observed, F(2,66) = 3.85, p < .05. Negative-Expectancy Group participants viewed the drum's rotation for more time than Positive-Expectancy and Placebo-Control Group participants (means of 866, 778, and 670 seconds, respectively, of a maximum of 960 seconds). Although only 27% of the Negative-Expectancy Group participants requested early termination of the drum's rotation compared with 41% of the Positive-Expectancy and 52% of the Placebo-Control Group participants, these differences were not statistically significant. Likewise, sex differences on these and all other outcome variables were not statistically significant, either within any group or among the entire sample of participants.
EGG Results
Six participants' EGGs contained so many movement artifacts that to perform an analysis on the remaining minutes would have produced unreliable results; these records were therefore excluded from the following analyses. A significant main effect of experimental period on percent gastric tachyarrhythmia was observed, F(2,120) = 23.96, p < .05. Gastric tachyarrhythmia was significantly greater across experimental groups during the drum rotation period than during both baseline periods but was not significantly different during the first and second baseline periods (Table 2). A significant main effect of experimental group on gastric tachyarrhythmia was also observed, F(2,60) = 5.67, p < .05. Gastric tachyarrhythmia was significantly lower among Negative-Expectancy Group participants than among Positive-Expectancy and Placebo-Control Group participants, but was not significantly different between Positive-Expectancy and Placebo-Control Group participants (Table 2). The interaction effect of experimental period and experimental group on gastric tachyarrhythmia was not statistically significant.
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Follow-up univariate ANOVAs examined differences between experimental groups at each experimental period. No significant differences in gastric tachyarrhythmia existed during either baseline period. During the drum rotation period, a significant effect of experimental group on gastric tachyarrhythmia was observed, F(2,60) = 7.86, p < .05. Gastric tachyarrhythmia was significantly lower among Negative-Expectancy Group participants than among Positive-Expectancy and Placebo-Control Group participants (Figure 4). The difference between Positive-Expectancy and Placebo-Control Group participants was not statistically significant (Table 2).
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DISCUSSION |
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The significantly greater gastric tachyarrhythmia among Positive-Expectancy and Placebo-Control Group participants than among Negative-Expectancy Group participants suggests the effects of placebo administration on subjective symptoms were accompanied by detectable differences in objective physiologic profiles. That is, the unanticipated effects of placebo-induced expectation on motion-induced nausea were not simply matters of symptom perception, but were genuine effects on gastric physiology as well. According to response expectancy theory (18), the interpretation of vague sensations as nausea may have contributed to the development of gastric dysrhythmia and increasing intensity of perceptions of nausea.
The failure of this experimental design to confirm the hypotheses and produce a traditional placebo/nocebo effect may be attributed to some important differences between this and other typical studies of the placebo response. Participants were not currently experiencing any symptoms when the placebos were administered. This certainly reduced the motivational element of a placebo effect for an ingested drug to provide relief from an unpleasant symptom (17). Also, none of the participants had experienced the stimulation provided by the rotating drum before, or taken any drugs to reduce symptoms provoked by the drum. According to the classical conditioning perspective of the placebo effect, these factors are necessary for a placebo response to occur (16,31). Finally, the placebos were not administered in a medical setting such as a hospital; the setting in which a medication is introduced likely serves as a powerful conditioned stimulus for the effect of that medication.
Explanations for the observation that Negative-Expectancy Group participants experienced the least severe nausea and motion sickness and that Positive-Expectancy Group participants did not differ from Placebo-Control Group participants are elusive; intuitively, however, the results do make a certain degree of sense with reference to the influence of preparedness or inoculation. Negative-Expectancy Group participants were told they should anticipate a sickening experience, but once the drum began to rotate, they may have experienced something far more innocuous than they had expected. Positive-Expectancy Group participants were led to believe their experience in the rotating drum would be fairly benign due to the pills they were given but soon realized it would be much more unpleasant than they came to expect. These important differences may have resulted in very different experiences for these two groups of participants. Those who unnecessarily braced themselves for a torturous ordeal may have been calmed or relaxed by what they experienced, whereas those who expected to feel fine may have been alarmed by or unprepared for what they confronted. These differences may have differentially influenced the development of nausea, motion sickness, and gastric dysrhythmia. Presumably, participants in each group experienced the same ambiguous, somewhat unsettling sensations during the early minutes of exposure to the rotating drum. Those who were alarmed by the sensations probably interpreted them as relatively severe and may have activated an unspecified psychophysiological mechanism that intensified the nausea and gastric dysrhythmia they were already experiencing. Those who were relieved by the sensations likely interpreted them as relatively mild, thereby leading to the minimization of nausea and motion sickness symptoms. These inferences are admittedly speculative and should be regarded as concepts in need of further investigation.
The discrepancy between the present results and what would be predicted on the basis of response expectancy theory might be reconciled by considering the dynamic process of the formation of expectations. Assuming that Positive-Expectancy Group participants formed a response expectancy for the development of few, if any, symptoms of nausea and motion sickness, it is likely that they modified their expectations once they perceived the slightest unwanted symptom. It is reasonable to suspect that expectations will constantly be adjusted as new information becomes available to an individual during exposure to any situation. Participants in the Positive-Expectancy Group may have reacted to the onset of symptoms by revising their expectations to that of relatively severe sickness. In contrast, Negative-Expectancy Group participants likely revised their expectations of severe sickness once they recognized the relatively benign nature of the situation. Although drawing this conclusion is beyond the scope of the data collected in this study, the possibility remains an intriguing one. The chief limitation of the study is the failure of participants' expectations to have been directly and accurately assessed following the administration of the manipulation or at any point during the study. Without these data, reasoned evaluations of the inferences drawn from the observed results are not easily made. Future studies should more carefully assess participants' expectations at several points during the course of an experiment.
In conclusion, the results of this study suggest being told that symptoms of nausea and motion sickness might be made worse by an ingested pill led to a reduction in the severity of nausea and motion sickness that later developed. Participants who were told the pills would offer protection from the development of nausea fared no better than participants told their symptoms would not be affected by the pills they ingested. Whether these results were influenced by differential expectations formed by participants in the three groups based on the different descriptions they heard of the pills they ingested is difficult to resolve. Hahn (23) emphasizes that care should be taken in assuming descriptions of an administered substance provided to patients or experimental participants will determine their expectations concerning development of or relief from symptoms. Participants bring with them their own expectations to the unfamiliar, ambiguous setting of the laboratory. Expectations provided by the experimenter and participants' own preexisting expectations likely interact to determine the participants' thoughts about a provided intervention. The processes of social interaction and communication can powerfully shape attention and perception and, in doing so, will have a dramatic influence on expectations that are generated. Kirsch (18) argues that the relationship between response expectancies and development of symptoms is strongly influenced by factors such as the strength of the expectation and the confidence with which one makes such predictions. Accounting for the level of ambiguity an individual perceives in the context of an eliciting stimulus might greatly facilitate the drawing of inferences concerning the effects of expectation on ultimate symptom development. The present study should be considered a cautionary tale by researchers in this area.
These results have implications for the psychological preparation of patients awaiting difficult medical procedures or any other potentially aversive situation. The extent to which patients are informed about what they will likely be going through over the course of an illness or treatment regimen may influence their ability to cope with the symptoms once they develop (32,33). If it can be demonstrated that expectations regarding the development of nausea in various evocative contexts can control the unpleasantness of the symptoms that later develop, there would be profound implications for the treatment of the many individuals whose illness and/or treatment involves the experience of nausea.
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Received for publication August 18, 2005; revision received December 12, 2005.
DOI:10.1097/01.psy.0000221377.52036.50
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