Vibrant and Healthy Kids Aligning Science, Practice, and Policy to Advance Health Equity (2019) / Chapter Skim
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2 Healthy Development from Conception Through Early Childhood
2 Healthy Development from Conception Through Early Childhood
Pages 77-140
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From page 77... ...
When the science of early development is coupled with a health equity approach to inform decision making, it provides an opportunity to improve outcomes for children and families in at-risk contexts. The goal of this chapter is to reveal core concepts of brain development and other systems relevant to understanding the impact of disparities on cognitive, social-emotional, and physical health and to describe new scientific advances in this area over the past 20 years.
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From page 78... ...
•• Certain body systems involved in cognitive and emotional development are more sensitive to early disturbances that activate stress response networks and provide a basis for both short- and long-term functional consequences of early life stress. •• Early adversity can change the timing of critical periods of brain develop ment, impacting the "plasticity" of developmental processes that are driven by experiences in the life of the young child and the family.
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From page 79... ...
In addition to the adverse effects of toxic stress on the brain and nervous system, it also affects every other organ system in the child's body, impacting short- and long-term health. spurred research to refine the fields' understanding of how environmental influences shape child development, even at a molecular resolution.
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From page 80... ...
, has negative impacts on selective brain circuits and emotional control, cognitive growth, and stress responsiveness. A new discovery from multiple animal studies shows that early adversity can change the timing of critical periods of brain development (Bath et al., 2016; Cameron et al., 2017; Hensch, 2016a; Heun-Johnson and Levitt, 2018)
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From page 81... ...
Composed of subsets of members of the From Neurons to Neighborhoods committee and the MacArthur Foundation Research Network on Early Experience and Brain Development, the Council has a central objective of communicating the science to the public and policy makers. Through an ongoing collaboration with the FrameWorks Institute on applying qualitative and quantitative research on communicating the science of brain and child development, a suite of effective "explanatory metaphors" has been developed, including a taxonomy of the stress response: positive, tolerable, and toxic stress (National Scientific Council on the Developing Child, 2014; Shonkoff and Bales, 2011)
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From page 82... ...
•• Cortex: The outermost region of the brain that exhibits the greatest expan sion in evolution, where billions of neurons reside, trillions of connections are made, and much of the brain's most complex computational activity takes place. •• Cortisol: A key hormone involved in the physiological stress response.
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From page 83... ...
•• Innate immune system: A portion of the immune system that removes foreign substances in tissues throughout the body and acts as a physical or chemical inflammatory barrier to infections but is not highly adaptable to a wide variety of infections. •• Intergenerational transmission of risk: The concept that epigenetic changes from certain behaviors in a parent may be transmitted from one generation to the next, separate and apart from the genes that are passed down through reproduction.
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From page 84... ...
can emerge, which could inform strategies for prevention-oriented interventions. The goal of this chapter is to provide essential information about the state of the science on human development from preconception through early childhood and some of the exciting findings in the past two decades within the fields of neurobiology, social psychology, epidemiology, and others that have contributed to advancing knowledge about how and when to intervene to improve outcomes for children.
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From page 85... ...
The committee could not be comprehensive with regard to coverage of all scientific advances, biological processes of healthy development, biological responses to stressors, and factors associated with individual differences, as each is a complex and active area of research. SCIENTIFIC AND TECHNOLOGICAL ADVANCEMENTS SINCE FROM NEURONS TO NEIGHBORHOODS The big questions driving research on child development and interventions to improve well-being are the same today as they have been for decades.
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From page 86... ...
2. Eye tracking, coupled with machine learning and neural network algorithms, has been used to discover patterns of scene viewing that serve as a sen sitive and specific signature to identify children who have normal facial morphology but were exposed to alcohol during fetal development and exhibit cognitive difficulties.
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. Initial discoveries recognized that epigenetic changes are chemical signatures (National Scientific Council on the Developing Child, 2010)
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Epigenetic changes occurring during preconception or during pregnancy can impact the germ cells of the offspring and result in intergenerational transmission of the parental experiences (Weber-Stadlbauer, 2017)
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From page 89... ...
Functional maturation of circuits continues throughout childhood, but connectome research, combined with genomics, has identified adolescence as a second period of dynamic changes in brain wiring.5 In humans, it is now understood that while classic diagrams of brain development present a well-delineated blueprint, there is far more variability in infants and toddlers than expected in the timing and extent of development of connectivity within the standard connectome blueprint. This basic neuroimaging research in humans has provided a foundation for determining the impact of disparities resulting from poverty and other social factors on the trajectory of brain growth and development of circuitry (Gabrieli and Bunge, 2017; Hanson et al., 2013; Johnson et al., 2016; Luby et al., 2012)
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From page 90... ...
. Intergenerational Transmission of Risk Evidence from both animals and humans indicates that adverse social/ psychological and physical exposures in one generation can alter risks for psychopathology, maladaptive behavior, and chronic disease in the next generation (i.e., the children of individuals who endured severe threat have elevated rates for psychiatric disorders and dysregulated physiology, despite an absence of direct exposure)
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From page 91... ...
At present, there is a limited understanding of how plastic or modifiable these intergenerational risk factors are and why some individuals are resilient to intergenerational risks whereas others are not. This is an area of active research that has elevated the importance of applying the life course approach to health and development, and by further understanding the pathways of both risk and resilience, scientists may uncover social, behavioral, or pharmacologic interventions that can interrupt the intergenerational transmission of the effects of stress on the developing embryo and fetus.
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From page 92... ...
Department of Education, numerous private foundations, and other agencies have resulted in a substantial growth in child development research using longitudinal data from prospective cohort studies with large subgroups of racial/ethnic minority children and stratified-probability samples. These studies have documented more extensively the pervasiveness of health disparities in these populations and the mechanisms by which these disparities arise.
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From page 93... ...
, upper- and lower-airway function, and obesity. Of note, many longitudinal studies of child development have been the product of interdisciplinary collaborations, which have become increasingly common.
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. Baby's First Years,7 launched in 2018 and funded by both private and public grants, is a new longitudinal study that seeks to establish causal links between parental income level and brain development in very young children.
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In addition to oxytocin's roles in the birthing process, lactation, and maternal care in mammals, studies have demonstrated that oxytocin (and its close neuropeptide relative vasopressin) facilitates affiliative social behavior through modulation of the activity of specific forebrain circuits (Feldman and Bakermans-Kranenburg, 2017; Hammock et al., 2005; Insel, 2010b; King et al., 2016; Numan and Young, 2016)
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From page 96... ...
have documented the importance of neighborhood contexts on family interactions and child development. Neighborhood context can be characterized as positive and negative, and it can reflect the physical or built environment and psychosocial characteristics.
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From page 97... ...
. Much of the impetus for the work on the effects of racism on children's development stemmed from the critical analyses of the prevalent use of the deficits model to understand health disparities in minority children (García Coll, 1990; McLoyd, 1990; Ogbu, 1981; Spencer and Markstrom-Adams, 1990)
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From page 98... ...
, which has the benefits of being lower cost and more efficient, although it can be limited by resolution and availability for a given temporal period. There has also been a substantial amount of research to examine child health in relation to neighborhood violence or crime, which can be derived from police crime reports (Beck et al., 2016; Goldman-Mellor et al., 2016; McCoy et al., 2015)
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From page 99... ...
This orchestrated temporal and spatial expression of genes depends on maintaining healthy cellular homeostasis and accessing nutrients that serve as the building blocks for proteins and eventually organ systems. Research has shown that regulation of fundamental metabolic processes, including mitochondrial function in the brain and periphery, is essential for cellular adaptations to developmental psychosocial stress that can impact mental and physical health (Eisner et al., 2018; Picard and McEwen, 2018)
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From page 100... ...
The following sections outline how several biological systems, those most relevant to this committee's report, develop between gestation and puberty and serve as a baseline for understanding how early envir onmental stressors and adversity affect child development and the emergence of health disparities: maternal physiological adaptations during pregnancy and the nervous, immune, endocrine, and reproductive systems. Note that in addition to psychosocial stressors in the environment of a developing child, adversity may include limited or no physical activity; exposure to toxicants, including alcohol and nicotine; and chronic disruption of bodily physiological functions, such as sleep (Feldman et al., 2014; Jones et al., 2019; McEwen and Getz, 2013; Thompson et al., 2009)
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From page 101... ...
. As we will discuss in Chapter 5, advancing health equity in birth and child health outcomes first requires improving preconception health for all women.
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From page 102... ...
However, chronic stress has been found to be associated with reduced activity and expression of placental HSD11B2, suggesting that the placenta's built-in ability to limit fetal exposure to maternal cortisol may be diminished in the face of chronic stress (Cuffe et al., 2012; O'Donnell et al., 2012; Welberg et al., 2005)
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From page 103... ...
synapse pruning HPA/endocrine tissue differentiation-secretions FIGURE 2-1 Human development of the brain and other organ systems from prenatal to pubertal periods. NOTES: Arrows represent time frames of approximate onset (darker shading)
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From page 104... ...
, which assumes synaptogenesis changes due to experience. In humans, more than 1 million synapses are added per second for this 2–3-year period (Center on the Developing Child at Harvard University, n.d.-a)
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The research also makes clear that brain development and maturation depends on experience -- what Greenough labeled "experience-expectant" development (Greenough et al., 1987)
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This occurs during a sensitive or critical period, when there is heightened plasticity for changes in the fine details of circuits that will establish functioning for a lifetime. Since that time, neuroscience research has shown that all sensory and motor circuits, as well as those involved in social and emotional behaviors, cognition, motivation and reward, executive functioning, and even stress responsiveness, develop through experience-dependent mechanisms that involve heightened plasticity.
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From page 107... ...
Molecules produced by the immune system impact various aspects of brain development, with strong evidence for mediating the formation and molecular adaptation of neural connections. The immune system also plays a role in the response of the brain
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From page 108... ...
. In the face of other challenges, the nervous system activates the HPA axis, which can lead to suppressed immune functioning and thus increased susceptibility to infections (Cohen et al., 2007; Thompson, 2014)
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From page 109... ...
. In contrast, high levels of maternal care documented in animal studies show that the stress response system is capable of better management of later-life stress (Meaney, 2001; Plotsky and Meaney, 1993; Plotsky et al., 2005)
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From page 110... ...
As noted above, animal studies show that intergenerational transmission of the impact of adversity during pregnancy can influence the mother, the fetus, and, if the developing gonads are affected, the offspring of the fetus when he or she matures into a reproductive adult. Sexual differentiation is controlled primarily by levels of testosterone, estrogen, and androgen, a process that can be influenced by exogenous chemicals similar in structure to these hormones.
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From page 111... ...
This stress response is a normal and healthy part of human biology. The spectrum of the stress response includes positive, tolerable, and toxic stress (Center on the Developing Child at Harvard University, 2005)
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From page 112... ...
Dysregulation of the Stress Response Severe or chronic activation of the stress response, in the absence of adequate caregivers who serve as buffers to the stress activation, can lead to disruption of homeostatic mechanisms and long-term changes to brain architecture and organ systems (the toxic stress response) (Shonkoff et al., 2012)
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Toxic Stress in Children and Adolescents, 403–428, Copyright (2016) , with permission from Elsevier.
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From page 114... ...
. Buffering the Stress Response From a population health perspective, ameliorating the toxic stress response and understanding the biological mechanisms by which toxic stress can be prevented or mitigated is of high priority.
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From page 115... ...
or prolonged exposure to chronic stress (such as poverty) can result in a chronically activated physiological stress response, which has a host of downstream consequences across biological systems.
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From page 116... ...
Conclusion 2-3: Research has changed the discourse to include scientific facts in child development that have determined that when considering the entire life course, it is early experiences, pre- and postnatally, that are the most powerful in working together with an individual's genetic makeup to influence the physical, mental, and cognitive development of the child. Science also shows that maternal health and well-being is a major contributing factor to the development of the fetus and establishes a foundation for positive or negative child health outcomes.
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From page 117... ...
In addition to the adverse effects of toxic stress on the brain and nervous system, it also affects every other organ system in the child's body, impacting short- and long-term health. Individual Differences in Responsiveness and Susceptibility Research over the past two decades clearly shows that what were previously considered to be universal developmental processes (see Chapter 4)
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From page 118... ...
. In animal studies, heritability of the behaviors that make up affiliative social behavior exhibits very similar genetic contributions (Knoll et al., 2018)
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From page 119... ...
Research is beginning to elucidate how risk factors at different time points may have varying impacts. Although it is generally accepted that developmental timing can influence the effect of a social or environmental risk factor on child health, the majority of studies do not consider how risk or protective factors vary by age.
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From page 120... ...
In summary, research advances in neuroscience, immunology, endocrinology, behavior, and psychology in the past two decades provide a new depth of understanding regarding the impact of adverse experiences on developmental processes throughout the life course. Because of these advances, the fields of developmental neuroscience, behavior, and psychology are recognizing the trajectories of development in the context
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Child Development. doi: 10.1111/cdev.13169.
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2003. The inflammatory response is an integral part of the stress response: Implications for atherosclerosis, insulin resistance, type II diabetes and metabolic syn drome X
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2014. A decade of science informing policy: The story of the National Scientific Council on the Developing Child.
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2015. The influence of the neighborhood physi cal environment on early child health and development: A review and call for research.
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Monographs of the Society for Research in Child Development 80(3)
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2016. Promoting healthy child development via a two-generation translational neuroscience framework: The Filming Interactions to Nurture Development video coaching program.
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2012. Early childhood adversity, toxic stress, and the role of the pediatrician: Translating developmental science into lifelong health.
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Child Development 58(3)
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2009. Social buffering of the stress response: Diversity, mechanisms, and functions.
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2014. Psychobiological mechanisms underlying the social buffering of the hypothalamic-pituitary-adrenocortical axis: A review of animal models and human studies across development.
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2018. The ingredients of healthy brain and child development.
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Child Development 88(2)
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Child Development 61:311–346. Meaney, M
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Child Development 81(1)
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Child Development 52(2)
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American Journal of Preventive Medicine 40(1)
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2011. Science does not speak for itself: Translating child development research for the public and its policymakers.
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2014. Stress and child development.
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American Journal of Community Psychology 53(1–2)
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Monographs of the Society for Research in Child Development 76(4)
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