A mood disorder is a group of conditions which are characterized by a disturbance in the person's mood. There are two primary types of mood disorders-major depressive disorder and bipolar disorder. The major depressive disorder also known as major depression is a disorder in which a person has more than one major depressive incident. Individuals with a major depressive disorder are at increased risk for suicide. Bipolar disorder is an emotional condition that is unstable and is categorized by cycles of abnormal, persistent high and low mood. Mood disorder can be treated with the help of therapy and medications such as behavior therapy, interpersonal therapy and cognitive therapy. This book aims to shed light on some of the unexplored aspects of mood disorders and the recent researches in this field. It consists of contributions made by international experts. This book will prove to be immensely beneficial to students and researchers in this field.