Socioeconomic conditions are known to be major determinants of health at all stages of the life course from pregnancy,1childhood,2 and adulthood.3 Life course epidemiology has added a further dimension to our understanding of the social determinants of health showing an association between early socioeconomic conditions and adult morbidity and mortality,4 and adult health related behaviours.5 Differential exposures over the life course are also likely to partly account for social gradients in health with the cumulative and additive effects of risk and protective factors exerting their effects over time.6

The causal debate related to the social determinants of health has been profoundly altered by recognition of the life course effects of early socioeconomic conditions. Single exposures, such as smoking, measured at a single time point can no longer be held to “account for” social differences in health. Multiple exposures operating over time seem to be implicated in …