Temperament and risk for mood disorders in adolescents

There has been longstanding interest in the role of temperament in the etiology and development of mood disorders (Akiskal et al., 1983; Klein et al., 2002). Work in this area is important for at least five reasons. First, the mood disorders are moderately heritable (McGuffin et al., 2003). Rather than coding directly for mood disorders, however, genes probably code for intermediate phenotypes that increase risk. Temperament traits associated with emotional experience, expression, and regulation may be intermediate phenotypes that are more tractable targets for genetic research than clinical disorders (Silberg & Rutter, 2002). Second, if temperament is associated with risk for mood disorders, tracing the pathways between temperament and mood disorder phenotypes can help elucidate more proximal processes involved in the development of these conditions. Third, temperament may provide a means to identify at-risk youth who could benefit from prevention and early intervention efforts. Fourth, temperament may be useful in identifying more homogenous subgroups of mood disorders and mapping the different developmental pathways that lead to mood disorder outcomes. Finally, there is substantial comorbidity between mood disorders and other forms of psychopathology, particularly anxiety disorders. Some temperament traits, such as negative emotionality (NE)/neuroticism (N), are associated with multiple psychiatric disorders. Thus, temperament could help explain patterns of comorbidity between classes of disorders and point toward more etiologically relevant classification systems (Clark, 2005; Khan et al., 2005). The incidence of mood disorders increases sharply in early adolescence, and the lifetime prevalence of mood disorders approaches adult levels by late adolescence (Nolen-Hoeksema, 2002).