The side effects of medications are most pronounced in individuals with high levels of neuroticism—those prone to anxiety, pessimism, and emotional instability. This finding was identified by psychologists from the University of Marburg. The results of the study were published in the Journal of Personality.
The researchers involved 275 healthy volunteers aged 18 to 65 in the experiment. Initially, participants completed questionnaires assessing neuroticism and reported on their health status. They were then divided into groups: one group received a placebo, while the other was given a 400 mg dose of the drug sulpiride, which at this level does not cause side effects in healthy people. Half of the participants on the placebo were warned that the medication might produce adverse reactions, while the other half were told they were taking a “harmless sugar pill.”
After a break lasting several hours, participants re-evaluated their condition. Neither the actual drug nor the experts’ warnings alone led to an increase in symptoms. The key factor turned out to be personality traits: participants with high neuroticism and strong expectations of side effects experienced the greatest increase in such symptoms.
The authors believe that only part of this connection is mediated by conscious expectation. However, in anxious individuals, heightened “body vigilance” also plays a role—meaning they are more attuned to natural bodily signals, such as stomach rumbling or mild weakness, and interpret them as side effects.
The authors recommend that doctors frame risks in a positive light: “95% of patients tolerate this medication without consequences,” rather than amplifying expectations by listing all possible complaints.
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