ABSTRACT
Epidemiology is defined as “the study of the distribution of a disease or a psychological condition in human populations and of the factors that influence this distribution” (1). Epidemiological surveys provide information that is essential in addition to the information obtained from clinical samples. First, they provide information about the prevalence, incidence, and rates of help-seeking behavior of the population. Second, representative samples of the general population provide a fuller description of all degrees of severity of a disorder than do clinical samples, which are generally subject to some form of self-selection due to help-seeking bias. Thus, information from epidemiological studies can be used to identify potential vulnerability factors for the development of a disease or disorder. Third, prospective, longitudinal studies of epidemiological samples can be used to investigate the course and clinical consequences of the disorder in the community. This information provides the basis for developing and evaluating preventive and other public health interventions.
