Commentary: Epidemiology? Keep it broad and deep

Zielhuis and Lambertus1 are asking us to draw a boundary around epidemiology that includes only so called ‘biological’ determinants of disease. They invoke no clear justification or claim any advantage for so doing. Needless to say their argument seems to assume that biology is scientific and that the social sciences like sociology and psychology are not, and they also implicitly connect biology with medicine. This is a normal part of a sloppy argument. Public health in the UK is currently likewise professionally protected for doctors, and hence it has come to be synonymous with public health medicine. Then the illegitimate protection is self-justified and the dominant protectors of the boundaries (the BMA in this case) no longer need to justify them, except when challenged. I believe we must resist (or simply ignore) this derivative proposal for similar reasons. Epidemiology is understanding the systematic determination of ill health by time, place and person. Firstly, it is the study of causes and determinants of disease and as such it must allow specialization within its boundaries to study, with enthusiasm, any plausible set of determinants. Secondly, most determinants interact in complicated ways, so even without specializing in social causes every epidemiologist must surely understand the rudiments of their potential effect. To exclude these experts by assigning them necessarily to another enterprise is simply stupid. To describe an epidemiologist who confronts questions from sociology as ‘merely a technician’ describes precisely why.