The primary focus of this project is to measure stress reactivity in infants of mothers' with major depression, a form of ELS, in a controlled laboratory setting. The literature is replete with studies of the effects of maternal depression, anxiety, and stress on infant well-being that includes >32,000 mother-infant pairs. Studies in infants with genetic vulnerability for affective disorders have been reported to have lower vagal tone, as well as higher salivary cortisol concentrations following lab tasks, when compared with control infants. There appears to be a mismatch between their passive or nonreactive behaviors, and their supersensitive physiological responses to stress. Remarkably, there are few investigations that have measured behavioral and psychophysiological functioning of infants of depressed mothers in response to controlled laboratory stress stimuli, and no study of this type has controlled for maternal co-morbid anxiety, maternal medications in pregnancy and/or lactation, obstetrical events, early life trauma and recent maternal stressful life events. This study is designed to further this important area of research by assessing behavioral and cortisol stress reactivity of infants of women with a history of major depression at six months of age. The prospective assessment of psychiatric morbidity during pregnancy and the postpartum period, comorbid anxiety, obstetric complications,early life trauma and maternal stressful life events will address the sparse date regarding maternal factors mediating infant reactivity. The study population will include 25 infants of women with no history of depression to serve as controls, that will be compared to infants from three age matched cohorts; 1) Women undergoing antidepressant treatment (monotherapy) for major depression during pregnancy and the postpartum period; 2) Women with a history of prenatal depression who choose not to take antidepressants; and 3) Women with a history of major depression who remain euthymic during pregnancy without antidepressant exposure. These later cohorts will be derived from ongoing NIH-funded investigations (Specialized Center of Research on Sex and Gender Effects focusing on PK/PD Modeling in Pregnancy and focusing on predictors of relapse of Depression during the Postpartum). At six months of age the infants will be exposed to laboratory stressors (noise burst, arm restraint), and their behavioral and physiological reactivity (heart rate variability, salivary cortisol) will be assessed. The novelty of these data is enhanced by the pre-natal and postnatal prospective assessment of variables that could influence response to these stressors.