Not that we didn't already know it, but now we know how it works chemically.
A collaborative research group including scientists from the Max Planck Institute for Medical Research in Heidelberg has demonstrated using mice that intensive maternal care during infancy promotes the effect of NPY in the brain. As a result of receiving such care, the animals were also less anxious in adulthood and weighed more than their counterparts who had received less affection. The research group was able to show that the effect is explained by the maternal care which stimulated the persistent formation of certain NPY receptors in the forebrain.
Neuropeptide Y (NPY) assumes several key roles in the brain's complex control circuits. The messenger substance not only influences body weight but also controls, among other things, the development of anxiety and stress responses. Hence NPY plays an important role in a series of mental illnesses such as post-traumatic stress disorders and anxiety disorders. NPY takes effect in the brain by binding to different docking sites on the neurons -- the NPY receptors. In this way, the hormone triggers signal cascades which control the different physical functions.