7. Genetic epidemiology

When looking for determinants of a disease we divide them, broadly speaking, into three categories: biology, behaviour and environment (see chap.​ 3). Genetic epidemiology is specifically concerned with the first category, and with the complex interactions between genetic factors and environmental or behavioural factors. It is thus closely related to molecular epidemiology, which is concerned with the role of biological or molecular markers of exposure and susceptibility, including DNA. Once the human genome had been mapped, interest in genetic determinants of disease – and hence in genetic epidemiological research – increased enormously. This is not the reason for devoting a separate chapter to this subspecialty in a general textbook of epidemiology, however: after all, this book does not include chapters devoted to the epidemiology of cardiovascular disease, psychiatric epidemiology, nutritional epidemiology or pharmacoepidemiology, to name but a few of many subspecialities. The reason for having a separate chapter on genetic epidemiology lies in the existence of specific biological mechanisms that apply to the transfer of genetic traits from one generation to the next. These make it possible to tackle questions regarding the genetic determinants of disease differently and more efficiently than other types of determinants. Consequently, genetic epidemiology uses some substantially different study designs and analytical methods in addition to the general epidemiological methods.