Trauma is a widespread, harmful and costly public health problem. It occurs as a result of violence, abuse, neglect, loss, disaster, war and other emotionally harmful experiences. Trauma has no boundaries with regard to age, gender, socioeconomic status, race, ethnicity, geography or sexual orientation. It is an almost universal experience of people with mental and substance use disorders. The need to address trauma is increasingly viewed as an important component of effective behavioral health service delivery. Additionally, it has become evident that addressing trauma requires a multi-pronged, multi-agency public health approach inclusive of public education and awareness, prevention and early identification, and effective trauma-specific assessment and treatment The effects of traumatic events place a heavy burden on individuals, families and communities and create challenges for public institutions and service systems. Although many people who experience a traumatic event will go on with their lives without lasting negative effects, others will have more difficulty and experience traumatic stress reactions. Emerging research has documented the relationships among exposure to traumatic events, impaired neurodevelopmental and immune systems responses and subsequent health risk behaviors resulting in chronic physical or behavioral health disorders.