Causality in the associations between exercise, personality, and mental health

Regular exercise is associated with mental health throughout the life course but the chain-of-causality underlying this association remains to be established. Does regular exercise actively improve mental health, or are there alternative explanations for this association? In this chapter, we show that part of the same set of genetic factors that influence whether people participate in regular exercise also affect mental health outcomes. Based on a review of published evidence we conclude that, in the population at large, the association between exercise participation and higher levels of life satisfaction and happiness and lower levels of anxiety and depression is not causal. Instead, these associations are best explained by underlying factors with a genetic etiology that influence both exercise behavior as well as mental health. New work in this chapter then examines the personality traits neuroticism and extraversion as a potential source of this genetic pleiotropy. Neuroticism behaves like anxiety and depressive symptoms in that its association with exercise behavior is due entirely to shared genetic factors. For extraversion, although part of its association to exercise is also due to shared genetic factors, we find support for a causal influence on regular exercise behavior.