This paper reviews recent research with animals which has cast new light on the mechanism and consequences of maternal attachment, and goes on to describe research in humans which has investigated the extent to which the same mechanisms may apply to us. It is clear that while some features of the adult are mediated by genes, environmental factors – notably good maternal attachment, are also of great importance. Stress during pregnancy can interfere with good maternal care with effects upon the hippocampus and the sensitivity of the infant's hypothalamo-pituitary-adrenal (HPA) axis. Interactions between gene expression and environment, between behaviour and genotype are important in the way they provide explanations of how the many different features that make-up the ‘depressive diathesis’ arise.