The role of personality in health has been under speculation for decades. The rise of coherent theories of personality and the inclusion of modern personality trait measures in large-scale epidemiological studies has only rather recently enabled to examine this question profoundly. Numerous studies have shown that from the five major personality traits, conscientiousness—describing individual differences, for example, in self-regulation, orderliness and carefulness—has emerged as maybe the most important personality factor in lifespan health with low consciousness being associated with a wide range of measures of health and well-being,¹ including reduced life expectancy.² This has sparked several calls highlighting the policy relevance of personality traits.^{3 4} However, personality traits are typically not included in health guidelines, and the potential causality between personality traits and health outcomes has remained inconclusive.

The study by Singh-Manoux et al⁵ makes an important contribution …