This document provides an overview of the history and foundations of psychiatric mental health nursing. It discusses definitions of mental health and mental illness from organizations like the WHO and APA. The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR) is introduced as the taxonomy used by mental health professionals for diagnosis. The development of institutions and community mental health in response to developments like psychopharmacology is summarized. Current issues like the high prevalence of mental illness and limitations of treatment access are also outlined.