This reference provides the results of a high-level task force created by the American Psychological Association - the largest professional society for psychologists in the United States - for the purpose of assessing the efficacy of therapeutic interventions for each of the major clinical disorders. The volume brings together all the outcome data and clinical trials, describing what works, what doesn't and what is not known. Among the disorders discussed are depression, anxiety, obsessive-compulsive disorders, substance abuse, and many more. As a reference work which integrates information from both clinical psychology and psychiatry, this work is intended as a desk reference for all practitioners.