Correlations between variables.

<div><p>A growing body of evidence suggests that questionable health behaviors- not following medical recommendations and resorting to non-evidence based treatments—are more frequent than previously thought, and that they seem to have strong psychological roots. We thus aimed to: 1) document the lifetime prevalence of intentional non-adherence to medical recommendations (iNAR) and use of traditional, complementary and alternative medicine (TCAM) in Serbia and 2) understand how they relate to ‘distal’ psychological factors—personality traits and thinking dispositions, and ‘proximal’ factors—a set of beliefs and cognitive biases under the term ‘irrational mindset’. In this preregistered cross-sectional study on a nationally representative sample (N = 1003), we observed high lifetime prevalence of iNAR (91.3%) and TCAM (99.2%). Irrational beliefs, especially magical health beliefs and medical conspiracy theories, were the strongest predictors of TCAM. They also mediated the relation between Disintegration/lower cognitive reflectiveness and TCAM. High Disintegration, and low Conscientiousness predicted iNAR directly, whilst negative experiences with the healthcare system facilitated both types of questionable health practices. The established psychological profile of people prone to questionable health behaviors and the fact they can be tracked to negative experiences with the system can be used to tailor public health communications.</p></div>