Neuroticism affects attitude to risk, decreasing willingness to take risks. As we noted, this result is in line with several previous findings connecting Neuroticism to a general adversity to uncertainty (Hirsh et al., 2008). Intelligence modulates the preferences over risky choices by reducing the difference in risk aversion between gain and loss domains, hence making the overall preference over risky outcomes more consistent.Source: Rustichini et al (July 2012).
One of the theories regarding evolutionary approaches to depression focuses on neuroticism. A moderate amount of neuroticism likely has certain beneficial effects such as increased drive and productivity due to greater sensitivity to negative outcomes and may increase a person's inclusive fitness but too much may reduce this by, for example, recurring depressions. Thus, evolution will select for an optimal amount and most people will have neuroticism near this optimum. However, since neuroticism likely has a normal distribution in the population, a minority will have very high (and low) neuroticism.HT: Matthew Baker.