Effects of adverse early-life events on aggression and anti-social behaviours in animals and humans

We review here the impact of early adversities on the development of violence and antisocial behaviour in humans, and present three etiological animal models of escalated rodent aggression, each disentangling the consequences of one particular adverse early-life factor. The review of the human data and those obtained with the animal models of repeated maternal separation, post-weaning social isolation and peripubertal stress clearly show that adverse developmental conditions strongly affect aggressive behaviour displayed in adulthood, the emotional responses to social challenges and the neuronal mechanisms activated by conflict. While similarities between models are evident, important differences were also noticed demonstrating that the behavioural, emotional and neuronal consequences of early adversities are to a large extent dependent on etiological factors. These findings support recent theories on human aggression, which suggest that particular developmental trajectories lead to specific forms of aggressive behaviour and brain dysfunctions. However, dissecting the roles of particular etiological factors in humans is difficult, as these occur in various combinations; in addition, the neuroscientific tools employed in humans still lack the depth of analysis of those used in animal research. We suggest that the analytical approach of the rodent models presented here may be successfully used to complement human findings and to develop integrative models of the complex relationship between early adversity, brain development and aggressive behaviour. This article is protected by copyright. All rights reserved.