This document provides information about depression, stress, and anxiety. It discusses the criteria for diagnosing major depression according to the DSM-IV-TR. It notes that depression can be caused by genetic and environmental factors, and describes research showing that early life stress and trauma can influence gene expression and increase the risk of depression through adulthood. The document also discusses the effectiveness of antidepressant medication and the brain mechanisms by which stress gets "under the skin" to impact long-term health.