The lack of side effects of an ineffective treatment facilitates the development of a belief in its effectiveness - PubMed


Fernando Blanco 1 ,

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The lack of side effects of an ineffective treatment facilitates the development of a belief in its effectiveness

Fernando Blanco et al. PLoS One. .

Abstract

Some alternative medicines enjoy widespread use, and in certain situations are preferred over conventional, validated treatments in spite of the fact that they fail to prove effective when tested scientifically. We propose that the causal illusion, a basic cognitive bias, underlies the belief in the effectiveness of bogus treatments. Therefore, the variables that modulate the former might affect the latter. For example, it is well known that the illusion is boosted when a potential cause occurs with high probability. In this study, we examined the effect of this variable in a fictitious medical scenario. First, we showed that people used a fictitious medicine (i.e., a potential cause of remission) more often when they thought it caused no side effects. Second, the more often they used the medicine, the more likely they were to develop an illusory belief in its effectiveness, despite the fact that it was actually useless. This behavior may be parallel to actual pseudomedicine usage; that because a treatment is thought to be harmless, it is used with high frequency, hence the overestimation of its effectiveness in treating diseases with a high rate of spontaneous relief. This study helps shed light on the motivations spurring the widespread preference of pseudomedicines over scientific medicines. This is a valuable first step toward the development of scientifically validated strategies to counteract the impact of pseudomedicine on society.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Two samples of the medical records used in the contingency learning task.

Medical records were presented sequentially (one new patient per trial). In these two samples, the fictitious patients were programmed to fail to recover. Thus, the outcomes for these two patients show the same symptoms as in the initial state of the trial (greenish skin, sweat) that was always presented in the top panel of each record. The record depicted in the top of the figure corresponds to a patient who was given the medicine by a participant in the high-cost group. The patient developed the skin rash side effect which was added to the symptoms of the syndrome. The record depicted at the bottom of the figure corresponds to a patient in which the participant decided not to use the medicine (the pill bottle is crossed out in red). This patient showed no additional symptoms to the ones provoked by the syndrome alone.

Figure 2
Figure 2. Stimuli used to represent the outcome information in the high-cost group.

These consisted of a picture and a message. Each patient either recovered from the crisis (left column) or not (right column). In addition, the cost (side effect) of the action was depicted as a permanent skin rash whenever it was used (top row). The skin rash was never observed otherwise (bottom row). In the no-cost group, regardless the decision to use the medicine, the stimuli were identical to those presented in the bottom row, except for the removal of the reference to side effects in the accompanying messages (i.e., “The patient has recovered from the crisis” or “The patient has not recovered from the crisis” for the left and right panels, respectively).

Figure 3
Figure 3. Results of the experiment.

The left panel shows the mean probability of introducing the potential cause, P(Cause), in each of the two groups. The right panel shows the mean effectiveness judgments given by participants in the two groups. Error bars depict 95% confidence intervals for the means.

Figure 4
Figure 4. Mediational structure underlying the experimental manipulation.

The total effect of the cost of the action on the effectiveness judgments, depicted as path c (top panel), is partitioned into two components, one indirect effect through P(Cause) (paths a and b, bottom panel), and one direct effect (path c', bottom panel), which is the result of discounting the indirect effect. The unstandardized coefficients and p-values for each pathway are provided. These results suggest that the effect of the cost associated with the treatment, manipulated between groups, was completely mediated by P(Cause).

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Grants and funding

Support for this research was provided by Dirección General de Investigación of the Spanish Government (Grant PSI2011-26965) and Departamento de Educación, Universidades e Investigación of the Basque Government (Grant IT363-10). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.