a childhood stage, health influences can act in very different ways because of the differing cultural interpretations that families attach to them.
While biology, behavior, and environmental categories are useful for organizing our discussion, it is important to understand that healthy development is not the product of single, isolated influences or even types of influences. Warm and nurturing parenting is an important family influence, but prematurity or visual impairment can make an infant unresponsive to a mother’s initial nurturing. Mothers may react with apathy or disinterest, which produces even more withdrawal on the part of the infant (Lozoff, 1989). While simplified schematics or models help to organize understanding of the influences on children’s health both during childhood and beyond, life is not as simple as these models suggest.
One caveat should be kept in mind in reading through the following review of evidence. Few of the cited studies drew their evidence from randomized experiments. And few if any of the nonexperimental studies included all relevant variables in their data and analyses. Thus, the findings reported in these studies are likely to suffer from exclusion of potentially important categories of influences, so that the associations that are reported as being important may be due to their associations with a more important or equally important characteristic, or due to interactions with other types of factors so that their effect may be manifested