The angst that reverberates in the character of Gil Buckman is not unfamiliar to many parents. Children enter this world sentient, to be sure, but otherwise, at least in parents' minds, entirely undifferentiated, with seemingly limitless potential. When we chose the time from birth to 5 years of age as a critical period of development for our theme issue, we did so hoping to attract articles that advanced the science of early life experience—articles that provided key, actionable evidence of how we can manipulate the early environment of children and make a tangible difference in their health. We clearly succeeded.

What have we learned? The birth weight of twin pairs appears to have important effects on later development, with larger twins having more conduct problems than the smaller infant of the pair.¹ Exposure to drugs and toxins during pregnancy and their effect on the developing fetus have long been of concern, and better understanding of these effects is one of the main driving forces behind the National Children's Study. Smoking during pregnancy has been shown to have myriad effects on infants and children; to these, we can now add sleep problems that persist throughout childhood.² For therapeutic agents, mothers and their physicians must balance the risk of the drugs against the risks—to both mother and child—of untreated disease. Oberlander and colleagues³ demonstrate that a third factor must be considered, namely, the child's genotype, which can have a moderating influence on the effects of maternal illness.

Another exposure that some would also classify as toxic to infants and young children is television. The obesity "epidemic" affecting children throughout the world has been ascribed, in part, to the effects of television on decreased physical activity and snacking while watching.^4-5 Pagani and colleagues⁶ show the harmful effects of each hour of television watched during the preschool years on classroom engagement and compare it with achievement in grade 4. The first experimental study of infant entertainment conducted in naturalistic settings found no evidence that entertainment designed for infants can increase a child's language development⁷ despite the claims of some producers of baby videos as well as a suggestion that earlier viewing might delay language, confirming prior studies.^8-9 Finally, articles in this issue advance our understanding of why low socioeconomic status has such detrimental effects on health. The worse cardiovascular health of overweight children from poor neighborhoods¹⁰ may be due to impaired reactivity and recovery from acute stress related to the high levels of chronic stress these individuals experience throughout childhood.¹¹

Caution needs to be emphasized in any interventions in children, and these interventions must be based on compelling evidence before being widely implemented. Screening of school children for attention-deficit/hyperactivity disorder would seem, initially, to be worthwhile. However, Sayal and colleagues¹² demonstrated that school screening offered no benefit to the children, and risks the harm of labeling children with a disorder.

What is especially gratifying is that articles in this issue show how changes in the environment can positively affect children. Nurse visitation programs for at-risk children show benefits, even 12 years later, both to the children who have less substance abuse, less internalizing of problems such as anxiety and depression, and better school performance¹³ as well as to their mothers, who also report less involvement with substance abuse and longer relationships with their partners.¹³ Perhaps the most vulnerable children in any society are those who are abused, orphaned, or in foster care. The nature of the environment in which society places these children can have enormous effects on the physical and emotional health of these children. Placing children involved with the child welfare system into foster care can lower the amount of stress the children experience, as measured by their diurnal cortisol secretion, compared with leaving them in the homes of their birth parents.¹⁴ Even more striking are the results of a randomized controlled trial¹⁵ of children living in institutional settings in Bucharest that emphasized the need for early placement of abandoned children in home-based care.

Taken together, the research in this issue has clear implications: early experiences matter, and changes in those experiences are achievable and pay dividends. This research needs to be translated into action. In the new austerity that has been spawned by the national fiscal crisis, states are cutting back broadly on services. In many cases, children are being hit the hardest. Given the importance of early childhood experiences on the entire life course, we can only hope that the people who make decisions about where monies are saved are mindful of the effect those decisions can have.

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Financial Disclosure: None reported.