Mental illness is prevalent in the USA and worldwide. This chapter focuses on poverty and perinatal morbidity as risk factors for mental illness, specifically the association of poverty experience in adolescence and low birth weight with depression in young adulthood. A report by Australia's National Health and Medical Research Council describes the full spectrum of perinatal morbidity, which includes frequent events such as maternal/infant separation due to admission to a special care facility, common conditions such as prematurity, low birth weight, and intrauterine growth restriction, and sentinel events such as major neurological or physical disability. Two depression measures are examined: the Center for Epidemiological Studies Depression (CES-D) scale of depressive symptoms and self-reported clinically diagnosed depression. Mental health is an important facet of overall health in adulthood, yet relatively little research has taken a life-course approach to understanding how illnesses such as depression develop.