Addiction is a brain disorder characterized by the inability to stop using a substance despite knowing that it is causing psychological and physical harm. It is a chronic condition that may arise from taking medications. Many people first engage in an activity voluntarily but addiction can take over and reduce self-control. Addiction can be of two types, namely, substance addiction and non-substance addiction. Most common examples of non-substance addiction are food, gaming, gambling, internet, sex and cell phone. Signs and symptoms of addiction are poor performance at work, declining grades or difficulty at school, a noticeable lack of energy in daily activities, inability to stop using a substance, profound changes in appearance, etc. This book discusses the recent researches in the field of addiction. From theories to research, case studies related to all contemporary topics of relevance to this field have been included herein. This book will serve as a valuable source of reference for graduate and post graduate students.