Based on years lived with disability, the World Health Organization ranks depression as the fourth largest global disease burden. Depression is one of the most frequent problems seen in psychotherapy. This book takes the reader through the central issues of diagnosis and treatment of depression. It begins with definitions and a readable explanation of the intricacies of depression diagnoses. Instruments for assessing depression as a diagnosis and as a dimension are described with their primary uses. Major theories are presented with their conceptions of depression and the implications of the conceptions for treatment. Today's empirically supported treatments for depression tend to be complex packages with sequences of different interventions. This book identifies the basic and common components of therapy for depression, i.e., the basic competencies that will allow professionals to treat most cases of depression. The book is aimed at students and professionals, giving them a comprehensive and up-to-date overview of psychopathology, assessment, and treatment of depression.