on Neuroticism and Agreeableness (18), and with younger people generally scoring higher on Neuroticism, Extraversion, and Openness, but lower on Agreeableness and Conscientiousness in most cultures (19). Furthermore, the five factors are predictors of important life outcomes (20, 21), including well-being (22), academic performance (23), vocational interests (24), marital stability and satisfaction (25), health risk behaviors (26, 27), and longevity (28). All five factors are related to personality disorders (29), and several researchers advocate a dimensional model in the upcoming DSM-V to reorganize the conceptualization and diagnosis of personality disorders (30). More generally, personality traits are thought of as risk factors, diagnostic indicators, and predictors of onset, severity, and outcome for most psychiatric disorders (31-33). These phenotypic links are supported at the genetic level; twin studies indicate that personality traits share a large proportion of genetic variance with depression and other disorders (31, 34-36). Personality traits are increasingly recognized as endophenotypes in genetic studies of mental disorders (7, 37).
