In many studies scientists claim that the early exposure to stress can cause a hippocampal remodeling (or atrophy) (Andersen & Teicher, 2004). The atrophy is a disbalance in the brainpart were one part is bigger than the other. The decreased hippocampus is also associated with a decrease in dendritic branching and neurogenesis. Neurogenesis is the development and growth of neurons (in short) and these neurons are important for functioning.
In a study done by Teichera et al. (2003) they come with two explanations for the reduced volume of the hippocampus. One explanation is that the reduced hippocampus volume is associated with adolescence alcohol abuse due to the child abuse. The other explanation they have is that it is not the childhood abuse causing the reduced volume, but a risk factor for the persistence of Post Traumatic Stress Disorder in adulthood. So they are already born with a slightly decreased hippocampus volume, but this gets more when child abuse is involved.
Andersen, S. L. & Teicher, M. H. (2004). Delayed Effects of Early Stress on Hippocampal Development. Neuropsychopharmacology 29,1988–1993
Teichera, M. H., Andersena, S. L., Polcarib, A., Andersona, C. M., Navaltaa, C. P. & Kim, D. K. (2003). The neurobiological consequences of early stress and childhood
maltreatment. Neuroscience and Biobehavioral Reviews 27, 33-44