ABSTRACT
Personality and intelligence – both partly heritable traits – are related to indices of health and disease. In this chapter we present literature showing that genes explain part of their associations. This finding is supported by both quantitative genetic (primarily twin studies) and molecular genetic (using information from genome-wide tests of common genetic polymorphisms) studies. This genetic relationship may arise from two potential mechanisms: mediated pleiotropy, whereby genes influence a trait that in turn influence another trait; or biological pleiotropy, whereby genes directly influence both traits. We discuss these potential mechanisms and describe methods which can help to test the competing explanations.
