The authors suggest that early abuse may be more damaging to developing emotion and stress systems because it happens as the brain is rapidly developing and when children are more dependent on caregivers' protection. Moreover, because it's harder for very young children to discern the clues predicting an abusive attack, they may be chronically stressed and overly vigilant, even when they're not being abused.

"In the United States, more than 1.5 million children are abused and neglected every year, though it's estimated that the actual rates are substantially greater," according to Dante Cicchetti, McKnight Presidential Chair and professor of child development and psychiatry at the University of Minnesota, who led the study.

"The results of this study have significant implications for children in the child welfare population and underscore the importance of providing early preventive interventions to children who have been abused."

Source: Society for Research in Child Development