Adding to the complexity of the problem, results of early maternal deprivation in mice also differ tremendously depending upon the genetic strain under examination. Additionally, the developmental period in which pups are separated radically alters the ensuing behavioral and physiological phenotypes, and consequences of early maternal separation can be altered or even masked by later periods of deprivation. The lack of consistency with regard to maternal separation in mice seems to be driven by at least two components: both the duration of separation and the quality of maternal care provided to the pups upon being returned to the nest. Indeed, studies examining the consequences of early maternal separation in mice have concluded that protocols similar to those used in rats are either without effect or fail to produce a reliable phenotype. The same 3 h period of separation in mice, however, often leads to an increase in maternal care potentially lessening the effects of separation itself. For instance, the standard 3 h of maternal separation of rat pups results in later alterations in hypothalamic-pituitary-adrenal axis (HPA) functioning, along with perturbations in several behavioral domains including fearfulness, attention, and anxiety. Examples in which experimental procedures have been successful in producing reliable behavioral effects in the offspring are plentiful, however, the majority of these cases examine rats (see for reviews but also see ). Although maternal separation is often used as a model of early life neglect, close examination of this literature in both mice and rats yields mixed results. Since the C57Bl/6 mouse genome has been sequenced and well annotated and numerous knockout and transgenic lines are available on this background, a mouse model using this strain would allow for in depth molecular analyses and, thus, would be ideal.

The use of a reliable animal model of early life neglect would be an invaluable tool for understanding the potential mechanisms resulting in ensuing behavioral and neurobiological changes. Unfortunately, the underlying molecular mechanisms of the consequences of early life neglect remain largely unknown. Indeed, recent studies have proposed a role for genetic factors in the establishment of behavioral effects of early life adversity.

Not all victims of abuse and neglect will go on to suffer adverse effects, however, suggesting that other factors may modulate the consequences of early life experience. Many individuals exposed to early life adversity go on to develop a variety of behavioral and psychiatric problems that persist well into adulthood, including both 'internalizing disorders', such as depression and anxiety, and 'externalizing disorders', such as drug and alcohol abuse, attention deficit hyperactivity disorder, and delinquency.

In the US, 24.4 out of every 1000 children will be abused or neglected within the first year of life, and neglect is far more frequent than abuse. Childhood adversity, in the form of abuse and neglect, is prevalent throughout the world and poses a significant public health problem.

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