This document provides an overview of abnormal psychology, including definitions of normal and abnormal behavior, a review of the historical approaches to understanding abnormality, perspectives from different schools of thought on explaining abnormal behavior, issues with classifying and diagnosing mental disorders, and how society views mental illness. It discusses the medical model used to diagnose, treat and cure mental illness, outlines several major mental disorders in the DSM-IV, and criticisms of the DSM. It also distinguishes between mental illness and insanity in legal terms, and addresses why abnormal psychology is studied and the goals of leading mental health organizations.