In regards to the question of whether a genetic predisposition for serotonin dysregulation interacts with stressful life events, we hypothesize that a genetic predisposition to serotonin dysregulation interacts with stressful life events in vulnerable individuals. For example, individuals with major depression (Kendler et al. 2005) or anxiety-related temperament (Pezawas et al. 2005) are thought to have reduced serotonin function at the level of the serotonin transporter (the transporter protein that most directly regulates serotonin function in the brain), making these individuals more sensitive to the effects of stressful life events (Anguelova et al. 2003; Kendler et al. 2005; Lotrich and Pollock, 2004). Recent findings in adolescents and young adults have shown that functional serotonin transporter polymorphisms interact with stressful life events to predict depression and suicidality (Caspi et al. 2003; Kendler et al. 2005; Eley et al. 2004), and substance abuse (Covault et al. 2007; Kaufman et al. 2004, 2006, 2007; Olsson et al. 2005).
