Mendelian randomization analysis of smoking behavior and cognitive ability on the Big Five

Tobacco smoke, a mutagen that can thin the brain’s cortex, might influence the Big Five (neuroticism, conscientiousness, agreeableness, extraversion, and openness). Cognitive ability, however, is a potential confounder, since it is associated with who smokes and with personality. Mendelian randomization (MR), which uses genetic variants as instrumental variables, can be used to probe the causal nature of these factors on personality. Here, MR was used to appraise smoking and cognitive ability on the Big Five and cognitive ability and neuroticism on social disparity. The results seem to suggest that smoking, independent of cognitive ability, leads people to be more neurotic and less extraverted and conscientious. Higher cognitive ability appears to make people less neurotic and more open, when accounting for smoking. Neuroticism appears to increase disparity, and higher cognitive ability appears to decrease it. Smoking may enhance disparity between those of lower and higher cognitive ability by exacerbating personality differences.