Negative affectivity and the influence of suggestion on asthma symptoms

Abstract

Objective

To investigate the effect of suggestion on subjective and objective asthma symptoms as a function of negative affectivity of the patients.

Methods

Asthmatics (n=32) took puffs from three separate placebo inhalers, being described as an inert (practice) substance, a bronchoconstrictor, and a bronchodilator. Negative affectivity, social desirability, probability of medication-intake, intensity of asthma symptoms and total respiratory resistance were measured at onset. The latter three measures were repeated after each trial. Heart rate, end tidal PCO₂, and breathing behaviour were measured during each trial.

Results

Asthmatics with high negative affectivity had overall more intense asthma symptoms. They also reported more airway obstruction after suggested bronchoconstriction and less after suggested bronchodilation, whereas persons with low negative affectivity did not show such variation. These effects were unrelated to social desirability. Respiratory symptoms correlated with the odds of medication intake. Neither negative affectivity nor suggestion influenced lung function and only breathing parameters under voluntary control changed as a function of suggestion.

Conclusion

Self-reported symptoms of asthmatics with high negative affectivity are more influenced by suggestion than those of patients with low negative affectivity.

Introduction

Asthma is one of the few medical areas where suggestion has been used as an essential part of a research paradigm. However, the term suggestion has been used in a number of ways. McDougall's definition (1908; see in Ref. [1]) of suggestion is one of the oldest: suggestion is a method of communication, resulting in the acceptance as convictive of the communicated proposition in the absence of logically adequate grounds for its acceptance. A more specific definition is the one proposed by Eysenck [2] who stated that suggestion occurs “when one person attempts to influence another person to believe something, to act in a certain way, or to perceive something along lines that are not congruent with reality. This influence has to be asserted indirectly, i.e., not through bribing or punishment, or attempting to influence him overtly”. From a cognitive–behavioural and social psychological perspective one mechanism responsible for the suggestion effect is referred to as “response expectancy” [3]. It is assumed that people have beliefs or cognitions about their own responses in a certain situation, generating subjective probabilities that nonvolitional subjective experiences and associated behavioural and physiological correlates will occur. These cognitions are influenced by verbal and contextual information.

The mechanism of response expectancy is particularly relevant to asthmatic patients: based upon previous experiences they learn to expect changes in symptoms in specific situations [4]. Case stories have been reported where asthmatics are indirectly confronted with certain eliciting factors (e.g., looking outside and seeing how cold it is outside) or given verbal information (e.g., being told that the doctor is on his/her way) resulting in changes in shortness of breath. To make scientifically sound deductions about the influence of suggestion in asthmatics, several paradigms have been developed. The most widely used method was first described by Luparello et al. [5] and McFadden et al. [6]. Subjects were told they were inhaling a bronchoconstrictor, but actually it was a relatively inert substance (saline). The effect of this intervention on lung function was then evaluated. A literature review [7] revealed that up to 35% of the subjects could be considered “responders” using a criterion of 20% change of pulmonary function (lung volume), which is considered to reflect a clinically significant airway change. Lewis et al. [8], however, showed that the observed suggestion effect was largely due to airway cooling in response to the inhalation of cool nebulized saline as a “neutral” substance. Controlling for this “saline-effect”, the subgroup of asthmatics objectively responding to suggestion, appeared much smaller [9]. A general finding in most studies was that subjects' perception of breathing difficulty was consistent with suggestions [8], [9]. Furthermore, there was no clear-cut correlation between subjective perceptions and objective measures of pulmonary physiology [8], [10].

The present study had several purposes. Firstly, as reported above, most studies' priority concern was the influence of suggestion on airway changes. When the patients' subjective symptoms were examined at all, they were assessed by means of a Visual Analogue Scale (VAS), resulting in a score that integrates several different aspects of asthma symptoms. In a previous study, we demonstrated that asthmatic subjects were able to describe their symptoms in terms of separate qualitative aspects, such as symptoms of airways obstruction, dyspnea, fatigue, hyperventilation symptoms, anxiety and irritation [11]. Secondly, the relationship between responsiveness to suggestion and negative affectivity (NA) was investigated. NA or the tendency to experience negative emotions has been found to correlate with elevated symptom levels and illness behaviour both in the general population and in several subgroups of patients [12]. Previously, we found that asthmatic patients characterized by high NA report more symptoms, regardless of their current clinical status [11]. There is no link between the personality trait neuroticism and physiological responses to suggestion [8], but its association with subjective responses to suggestion has not been explored yet. Because elevated symptom levels in high NA subjects have been explained by symptom perception variables, such as attentional bias to internal state [13], it may be hypothesized that NA modulates the effect of suggestion. Thirdly, we wanted to explore the extent to which suggestion of airway changes would lead to changes in the intention of medication intake. Lastly, we wanted to differentiate a subjective suggestion effect from the concept “social desirability”. Considering response expectancy as an important part of suggestion, one could suspect that a mechanism such as social desirability, defined as a deliberate intention to comply with the expectation of the experimenter/doctor, would explain the symptomatological responses to suggestion.