Medicine-related beliefs predict attribution of symptoms to a sham medicine : a prospective study

Objectives

To investigate a range of possible predictors of nocebo responses to medicines.

Design

Prospective cohort study.

Methods

In total, 203 healthy adult volunteers completed measures concerning demographics, psychological factors, medicine‐related beliefs, baseline symptoms, and symptom expectations before taking a sham pill, described as ‘a well‐known tablet available without prescription’ that was known to be associated with several side effects. Associations between these measures and subsequent attribution of symptoms to the tablet were assessed using a hurdle model consisting of a joint logistic and truncated negative binomial regression.

Results

Men had an increased odds of attributing symptoms to the tablet OR = 1.52, and older participants had decreased odds, OR = 0.97. Medicine‐related beliefs were important, with modern health worries, belief that medicines cause harm and perceived sensitivity to medicines associated with increased odds of symptom attribution, OR = 1.02, 1.10, 1.09, respectively. Trust in medicines and pharmaceutical companies decreased the odds of symptom attribution, OR = 0.91, 0.88, respectively. The number of symptoms at baseline and the expected likelihood of symptoms were associated with an increased odds of attributing symptoms to the tablet, OR = 1.07, 1.06, respectively. Anxiety, previous symptom experience, symptom expectations, and modern health worries were also important in predicting the number of symptoms participants attributed to the tablet.

Conclusion

It is hard to predict who is at risk of developing nocebo responses to medicines from demographic or personality characteristics. Context‐specific factors such as beliefs about and trust in medicines, current symptoms and symptom expectations are more useful as predictors. More work is needed to investigate this in a patient sample.