Early-Life Circumstances and Their Effects Over the Life Course.

The idea that early-life circumstances shape people’s health, development, and well-being over the life course has gained renewed centrality in the last two decades. This renewed interest has been informed by new approaches that emphasize sensitive and critical periods during the first years of life, offer an understanding of human development as a hierarchical and cross-fertilizing process, suggest plausible mechanisms for the persistent effect of early exposures, and explore heterogeneity in effects based on environmental and biological factors. The articles included in this special issue of Population Research and Policy Review advance the field of early-life circumstances in several important dimensions. They examine the determinants and effects of noxious exposures at different developmental stages—ranging from the prenatal period to adolescence—in a variety of national settings. They offer an understanding of early-life circumstances that moves from discrete outcomes to a dynamic life-course approach, and consider diverse sources of heterogeneity in the effects of early exposures.