This book introduces readers to a more comprehensive and empirically based approach to psychopathology than any other approach in use by psychological professionals today. It incorporates all areas of psychological research, experimental and observation as well as clinical and medical. This approach presents a method that does not entirely replace methods like those in the DSM-5 but improves them. Comparative psychology, the study of behavior across all species, has a solid place in this approach because it is where behaviors and psychological processes are studied in the most objective and empirically-sound manner. Areas covered throughout this text include not only the history of comparative psychopathology and comparative psychopathology as an approach to understanding psychological disorders, including anxiety and depressive disorders, better but also how comparative psychopathology can help advance psychology's understanding of terrible social ills, including poverty and violence. By reading this text, readers will find essential information about how incorporating comparative psychology into understanding psychopathology can make that understanding stronger and how this approach can help psychology make for a truly better and just world.