The Causal Effect of Personality Traits on the Mental Health in Breast Cancer Patients Under the Occurrence of Negative Life Events

Using longitudinal data from Portugal, Italy, Finland, and Israel, this article attempts to explore the causal relationship between mental health and the Big Five personality traits of breast cancer patients with the appearance of adverse life events. The main conclusion is that patients with high scores in the Big Five personality traits index enjoy better mental health status than patients with low scores in that index. In addition, there is a significant negative correlation between mental health deterioration and personality traits as an index and as individual traits. The negative impact on the mental health of cumulative adverse life events is significant and cannot be moderated by personality traits. Single negative life events have a positive correlation with mental health status deterioration, though not all of them are significant and only work-related problems can moderated significantly by high scores in the personality trait index. Moreover, the most important control variable are the state of exercise, which if it changes from active to not active causes a significant drop in the mental health score and cancer stage. Lastly, this causal relationship is validated by the prediction accuracy of AI/ML models.