Childhood adversity and neural development: deprivation and threat as distinct dimensions of early experience

Abstract

A growing body of research has examined the impact of childhood adversity on neural structure and function. Advances in our understanding of the neurodevelopmental consequences of adverse early environments require the identification of dimensions of environmental experience that influence neural development differently and mechanisms other than the frequently-invoked stress pathways. We propose a novel conceptual framework that differentiates between deprivation (absence of expected environmental inputs and complexity) and threat (presence of experiences that represent a threat to one's physical integrity) and make predictions grounded in basic neuroscience principles about their distinct effects on neural development. We review animal research on fear learning and sensory deprivation as well as human research on childhood adversity and neural development to support these predictions. We argue that these previously undifferentiated dimensions of experience exert strong and distinct influences on neural development that cannot be fully explained by prevailing models focusing only on stress pathways. Our aim is not to exhaustively review existing evidence on childhood adversity and neural development, but to provide a novel framework to guide future research.

Figure 1. Dimensions of threat and deprivation associated with commonly occurring adverse childhood experiences (ACEs)

¹ Importantly, we argue that threat and deprivation are dimensions of experience that can be measured among children exposed to a wide ranges of ACEs, both those that occur in isolation (e.g., a single incident of community violence exposure) and those that are co-occurring (e.g., physical abuse and physical neglect). We use the term complex exposures to refer to experiences that in most cases involve aspects of both threat and deprivation. Institutionalization is one such exposure, which involves deprivation in both cognitive and social inputs—consistent with our definition of deprivation—as well as the absence of a primary attachment figure, which is an atypical experience that can represent a significant threat to safety and survival for an infant in the extreme absence of care. Note that institutional rearing also involves lack of species-typical expectations of the presence of an attachment figure in early development (Tottenham, 2012), a dimension not fully captured by either deprivation and threat. ² Poverty differs in fundamental ways from the other exposures we describe. Critically, poverty does not inherently involve dimensions of either threat or deprivation (i.e., it is possible to be poor and to have no exposure to threatening experiences and typical exposure to cognitive, social, and environmental complexity). However, poverty is often a marker of exposure to both threat and deprivation, particularly deprivation in exposure to enriching and cognitively complex environments. Because the degree of threat and deprivation exposure associated with poverty is heterogeneous, this could be one reason that the findings with regard to poverty and neural development have been inconsistent across studies.