[The epidemiological method in the field of mental health].

The role of epidemiological methods in clinical practice and research are discussed in this article. In particular, the main applications of the epidemiological approach in the field of mental health are illustrated. First, it has been possible to investigate the prevalence and incidence of mental disorders outside specialist settings (general population and primary care services); this allowed for a better definition of the spectrum of mental disorders beyond the most severe ones which are usually treated by psychiatrists. In this way, incidence and prevalence studies contributed to the identification of groups of subjects at risk for mental disorders to be provided with prevention and treatment programs. Second, data from epidemiological studies contributed to the development of classificatory systems with high reliability and validity to be used in clinical practice and research activities. Third, epidemiological data are often integral part of theories concerning the origin, course, outcome, and treatment response of disorders. Fourth, the comprehensive and longitudinal evaluation of service activity is necessary to introduce possible changes in the organization of the health care system and to allocate available resources. Finally, it is recommended that epidemiological research could maintain a real integration with clinical practice and develop a strong collaboration with other disciplines such as genetics, psychology, sociology and anthropology.