Mental disorders have profound social, cultural, and economic effects throughout the world. Although most psychiatry and psychology texts provide some basic data on the prevalence and treatment of mental disorders, no previous book ever presented such data with the breadth or depth of the current volume. Reported here are the first results of the WHO World Mental Health (WMH) Survey Initiative, a highly ambitious series of cross-national psychiatric epidemiological surveys. The general population surveys in the WMH series span 17 countries in all parts of the world. In many of these countries the WMH surveys provide the first community epidemiological data ever available on mental disorders in the population. The detailed information on lifetime prevalence, age of onset, course, correlates, and treatment of mental disorders in this volume provides mental health professionals and healthcare policy planners with an unprecedented reference on the cross-national descriptive epidemiology of mental disorders.