General intelligence, disease heritability, and health: a preliminary test

Cognitive epidemiology shows that more intelligent individuals stay healthier and live longer, but it is not known why. The system integrity theory predicts that more intelligent individuals are more protected from diseases that are more heritable, while the evolutionary novelty theory predicts that they are more protected from diseases that are less heritable. The paper proposes a new method of testing the competing hypotheses. An analysis of two large-scale population data sets from Sweden ( n= 1 million for individual data and n= 9.6 million for heritability data) shows that intelligence is more important for health when the cancer heritability is low, supporting the evolutionary novelty theory. While the present results are merely suggestive, not conclusive, the proposed method can be extended to include other diseases and causes of death.