Fig. 1.

A directed acyclic graph demonstrating the difference between a confounder and a collider within the context of this study. The figure illustrates two possible scenarios when conditioning on self-reported health in the analysis between neuroticism and risk factors for mortality: (a) Self-reported health is a confounder that influences both neuroticism and risk factors for mortality and is therefore appropriate to condition on; (b) self-reported health is a collider that both neuroticism and risk factors for mortality influence, thereby potentially leading to spurious findings when conditioned on. BMI = body mass index.