Although correlations between personality and health are consistently observed, often the causal pathway, or even the direction of effect, is unknown. Genes provide an additional node of information which may be included to help clarify the relationship between personality and health. Genetically informative studies, whether focused on family-identified relationships or specific genotypes, provide clear benefits to disentangling causal processes. Genetic measures approach near universal reliability and validity: processes of inheritance are consistent across cultures, geography, and time, such that similar models and instruments may be applied to incredibly diverse populations. Although frequency and intercorrelations differ by ancestry background (Novembre et al., 2008) and cultural context (Tucker-Drob & Bates, 2016) may exert powerful moderating effects, fundamental form and function is consistent across all members of our species, and even many other species. Genetic sequence information is also of course highly temporally stable, and possesses temporal precedence. That is, the literal genetic sequence is lifetime-stable and comes before all other experiences. Human behavior genetic research, like most personality research, faces limitations in terms of causal inferences that may be made in the absence of experimental manipulation. But behavior genetics takes advantage of natural experiments: populations that differ in terms of genetic similarity (either inferred – such as twins – or measured – such as genotyping methods) to begin to unravel the complex influences on individual differences in personality and health outcomes.
