This document provides an overview of abnormal psychology. It defines abnormality and discusses how abnormal behavior has been viewed throughout history from ancient to modern times. Key topics covered include the classification of mental disorders in the DSM and ICD manuals, specific disorders like mood disorders, anxiety disorders, and schizophrenia, and perspectives on the causes of mental illness like biological, psychological, and social factors. Defenses mechanisms, treatment approaches in ancient times, and what defines normal behavior are also addressed.