[Genetic epidemiology: its use in psychiatric research]

Psychiatric disorders, a growing health concern, are believed to occur due to the interaction of multiple factors. Identification of the causes of psychiatric disorders and related risk factors will increase the efficiency of the development and implementation of relevant preventive measures. Genetic epidemiology studies the frequency, distribution and causes of diseases and enables one to investigate how genetic and/or environmental factors interact in producing the complex phenotypes of various disorders. Genetic research is often initiated when a clinician detects similar cases of psychiatric disorders among relatives of patients admitted to the clinic and/or when the frequency of a particular disease is found to be significantly higher than expected in a particular group of the population or place or at a particular time. High occurrence rates of a particular psychiatric disease could reflect a genetically transmitted disorder, could be due to familial aggregation of disease risk factors, or could be linked to another genetically transmitted disease. Preceding comprehensive genetic research, the role of chance, bias, and confounding factors should definitely be excluded. This review summarizes the epidemiologic study designs used to investigate the role of genetic structure in the occurrence of psychiatric disorders, the issues to be considered in designing and conducting such studies and potential sources of error.