Genetic epidemiology is the study of the role of genetic factors in determining health and disease in families and in populations, and the interplay of such genetic factors with environmental factors. Genetic epidemiology seeks to derive a statistical and quantitative analysis of how genetics work in large group. The use of the term Genetic epidemiology emerged in the mid 1980s as a new scientific field. In formal language, genetic epidemiology was defined by Newton Morton, one of the pioneers of the field, as "a science which deals with the etiology, distribution, and control of disease in groups of relatives and with inherited causes of disease in populations".It is closely allied to both molecular epidemiology and statistical genetics, but these overlapping fields each have distinct emphases, societies and journals.
One definition of the field closely follows that of behavior genetics, defining genetic epidemiology as "the scientific discipline that deals with the analysis of the familial distribution of traits, with a view to understanding any possible genetic basis", and that "seeks to understand both the genetic and environmental factors and how they interact to produce various diseases and traits in humans". The BMJ adopts a similar definition, "Genetic epidemiology is the study of the aetiology, distribution, and control of disease in groups of relatives and of inherited causes of disease in populations.
Modern genetics began on the foundation of Gregor Mendel's work. Once this became widely known, it spurred a revolution in studies of hereditary throughout the animal kingdom; with studies showing genetic transmission and control over characteristics and traits. As gene variation was shown to affect disease, work began on quantifying factors affecting disease, accelerating in the 20th century. The period since the Second World War saw the greatest advancement of the field, with scientists such as Newton Morton helping form the field of genetic epidemiology as it is known today, with the application of modern genetics to the statistical study of disease, as well as the establishment of large-scale epidemiological studies such as the Framingham Heart Study.