In addition, two other specific causal mechanisms have been hypothesized through which neuroticism may be linked to physical health problems that may not be involved in mental health problems. First, it is possible that higher neuroticism is associated with greater sympathetic and hypothalamic-pituitary-adrenal (HPA) reactivity and with greater alterations of the immune system in response to stressful life events (Futterman, Kemeny, Shapiro, & Fahey, 1994; Gillespie et al., 2004). In turn, these enhanced physiological responses to stress may contribute to health problems (Contrada et al., 1999; Friedman, 2000;T. W. Smith & MacKenzie, 2006). Second, it is likely that persons high in neuroticism are more likely to engage in behaviors that increase the risk of health problems (Contrada et al., 1999).
