Child abuse shrinks key brain memory centre

 Maltreatment of children may stunt growth of the hippocampus, a brain region vital for memory. That's the conclusion of a study of 193 outwardly healthy adults aged 18 to 25 from the Boston area.

The stunted hippocampi could help explain how childhood stress raises the risk of psychiatric disorders in adulthood, ranging from depression, schizophrenia and post-traumatic stress disorder to personality disorders, drug addiction and even suicide.

Martin Teicher of McLean Hospital in Belmont, Massachusetts, and colleagues used standard questionnaires to reveal which volunteers had suffered abuse as children, and found size differences in regions of the hippocampus through detailed MRI brain scans.

Big differences were seen in people who said that as children they had experienced verbal, physical or sexual abuse, physical or emotional neglect, bereavement, parental separation or parental discord. Three sub-regions of the hippocampus were between 5.8 and 6.5 per cent smaller in such volunteers, compared with those who reported no maltreatment.

Stress strike

The three sub-regions – the dentate gyrus, the cornu ammonis and the subiculum – are all known to be vulnerable to the effects of stress hormones, which probably interfere with the formation of cells and new tissue as the immature brain develops.

"These findings support the hypothesis that exposure to early stress in humans, as in other animals, affects hippocampal development," concludes Teicher's team. They say that the study is the largest and most detailed yet to examine the phenomenon in people, and the results echo those seen in the hippocampi of rats and monkeys subjected to stress as infants.

Child abuse or poverty can also alter which genes are active in the developing brain through a process called epigenesis. These changes can lead to diseases such as schizophrenia and bipolar disorder.

"Childhood maltreatment is like a surgical strike on the brain," says Carmine Pariante, who studies the effects of stress on child development at the Institute of Psychiatry, Kings College London. "This explains why these individuals are at risk of developing a host of stress-related disorders later in life – because they have an impaired ability to cope with stress."

"Findings like this indicate that maltreatment can leave damage hidden deep inside the body that persists for many years," says Terrie Moffitt of Duke University in Durham, North Carolina. "Once we appreciate that child maltreatment brings hidden damage that can resurface years later as memory problems, preventing child abuse seems like a very good deal."

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1115396109

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