A Mendelian Randomization approach for studying the possible involvement of evolutionarily relevant personality traits in the development of cancer

To define personality traits Five Factor Model (FFM) is the most accredited and used worldwide. It divides personality into five main domains: Agreeableness, Conscientiousness, Extraversion, Neuroticism and Openness. Today, questionnaire based on the FFM are standardized and reliable, and give important information about individual differences in personality. From an evolutionary point of view, these traits are thought to have been evolved because they are fundamental in solving adaptive problems in a complex social system. The drastic change in the lifestyle characterizing our modern society may have changed the adaptive role of personality. If this is true, personality traits could have become possible risk factors for cancer development. The relationship between personality and cancer has long been hypothesized. Personality traits are known to be associated with lifestyle and social behaviour. Personality traits have a genetic component that accounts for heritability of about 40 percent. Genome wide association studies (GWASs) have searched and found some of the genetic variants associated with each of the five personality traits. The increasing availability of personality-associated genetic variants has been central to the study of a possible causal association between personality and cancer, through a recent method called Mendelian Randomization (MR). Using MR, possible causal associations between the five personality domains and 10 cancer outcomes (breast, colorectal, pancreatic, lung, ovarian, oesophageal, bladder, multiple myeloma, glioma, and prostate cancer) were investigated. After correction for multiple testing (p < 1 x 10-3) no association was statistically significant. Association between neuroticism, conscientiousness ad openness with pancreatic risk cancer were extremely close to the p-value threshold. Neuroticism and openness increase the risk with an OR = 1.42 (95% CI 1.09-1.85), p = 0.009, OR = 1.10 (95% CI 1.04-1.17) and p = 0.002, respectively. Conscientiousness decreases the risk with an OR = 0.96 (95% CI 0.93-0.98) and p = 0.002. In light of the results of this study, the impact of personality traits on cancer incidence still remains unclear. More studies with greater statistical power will be needed to show a possible causal relationship