Psychiatric disorder refers to a behavioral or mental pattern, which causes significant distress or impairment of personal functioning. These features can be remitting, persistent and relapsing or may happen as single episodes. Some of the prominent symptoms of psychiatric disorders are excessive fear and worry, poor concentration, feelings of excessive guilt or low self-worth, and alternating depressive episodes with periods of manic symptoms. The area of medicine which studies the nervous system tissues in order to diagnose diseases is known as neuropathology. Organic brain diseases and degenerative diseases exhibit clear morphological and neurohistological abnormalities, and can be efficiently studied within the domain of neuropathology. However, psychiatric illnesses generally do not manifest homogenous brain pathology, and research is ongoing in studying the neuropathological mechanisms of psychiatric disorders. This book presents the symptoms and neuropathological mechanisms of psychiatric disorders. It presents researches and studies performed by experts across the globe. The extensive content of this book provides the readers with a thorough understanding of the subject.