Maltreatment, neglect or other stressful experiences early in life are known to produce impairments in social, behavioural and cognitive functioning. The brain is also known to be vulnerable to stress and the hippocampus, amygdala and corpus callosum are all known to be affected by early exposure to negative or stressful experiences. Researchers from the Institute of Psychiatry in London looked into the effects of early stress on the brain by comparing a group of children brought up in state orphanages in Romania and subsequently adopted to a control group of children brought up in families in the U.K. The conditions of care in the orphanages were pretty grim with the children remaining in cots all day, with few playthings, little interaction with adults and being fed gruel through a bottle. The study found that the Romanian children had significantly smaller grey and white matter volumes. The Romanian children had larger amygdalas, relative to the size of their brains, although this was because the right amygdala was larger as the left amygdala was actually smaller in the Romanian children. There were no differences in the hippocampus and the corpus callosum between the two groups.
Mehta, Mitul A. ... [et al] - Amygdala, hippocampal and corpus callosum size following severe early institutional deprivation: the English and Romanian adoptees study pilot Journal of Child Psychology and Psychiatry August 2009, 50(8), 943-951