Periodic blood draws will be used to assess biosignatures of depression. Guiding our investigations of pharmacogenetics, inflammation, and proteomics are synergistic interactions among the serotonergic system, the HPA axis, systemic inflammation, growth factors such as brain derived neuro-trophic factor (BDNF), psychosocial stressors, and vascular co-morbidity. Genetic variation in vasopressin receptors, potentially involved in both cardiovascular risk and social attachment, is also associated with recurrence of depression. Similarly, genetic variation in inflammation may influence antidepressant response and medical co-morbidity.