Unipolar major depressive disorder (MDD) is a debilitating condition with a lifetime prevalence rate of 17% (Kessler et al., 1994). Recent epidemiological evidence indicates that MDD is the 4th leading cause of disease burden and the leading cause of disability-adjusted life years (Ustun, Ayuso-Mateos, Chatterji, Mathers, & Murray, 2004) and is associated with significant psychosocial and medical morbidity and mortality (Kovacs, 1996). MDD is characterized by a high rate of relapse, with approximately 40% of patients reporting relapse within 2 years (Solomon et al., 2000) and 85% within 15 years (Mueller et al., 1999). With each new episode of major depression, the likelihood of experiencing future episodes increases by 16% (Solomon et al., 2000). Given the chronic nature of MDD, a critical goal for treatment development is to target the core processes that make an individual vulnerable to depressive episodes and thus improve his/her resilience to future depression.