OBJECTIVE: In the last two decades, a multitude of investigations into the frequency of mental disorders in the population have emerged, making it difficult to keep track of recent findings and tasks. Building on a historical review, the present study provides a comprehensive overview of knowledge about the prevalence of mental disorders. METHOD: The review is based on current national surveys with comparable methodology. Study selection, based on a consecutive literature search through August 2005, led to the inclusion of Australian, German, Dutch and US-American (NCS; NCS-R) surveys of mental disorders in the general population. RESULTS: A considerable proportion of the population is found to have a mental disorder. The most frequent disorders within the preceding 12 months are mood disorders (6.6-11.9%) and anxiety disorders (5.6-18.1%). Substance disorders (3.8-11.3%) and somatoform disorders (11.0%) are also very frequent. The prevalence rates presented in each survey are dependent on the specific disorders included and the classification system underlying them. Important risk factors are being female, being unmarried, being unemployed and having a low social status. CONCLUSIONS: Knowledge about mental disorders in the general population can contribute to bringing about considerable improvement in the treatment of mental disorders. In addition to available knowledge, however, there is a continued need to address existing challenges from both a methodological and content-related perspective, e.g. the lack of or inadequate inclusion of specific disorders, the lack of prevalence rates of mental disorders in childhood and adolescence, and the as yet only rare inclusion of personality disorders.
