Post-traumatic stress disorder, in the news lately because of the growing number of Iraq and Afghanistan war veterans exhibiting its symptoms, may have a link to brain-matter loss sustained in childhood injury or abuse and may linger into adulthood.

The extent to which the lost brain matter affects brain function is still unknown, but a Brigham Young University research team has found that traumatic events and PTSD symptoms can be linked to a size reduction in the hippocampus, a key part of the brain involved in learning and memory.

The study appears in the August issue of the neuroscience journal Hippocampus, and it adds to growing evidence of a neurological component for the often debilitating mental disorder.

Researchers didn't focus on war veterans, who are the center of attention for much of the scientific research and news coverage. Instead, they looked at a population much bigger and likely to have experienced a trauma injury: abused children.

"The size reduction in the hippocampus seems to occur sometime after the initial exposure to stress or trauma in childhood, strengthening the argument that it has something to do with PTSD itself or the stress exposure," said Dawson Hedges, a BYU neuroscientist and an author on the study. "Most people exposed to traumatic events do not develop PTSD. However, those who do develop the disorder may show certain changes in their brains."

Since scientists first detected signs of a smaller hippocampus among some people with PTSD some 10 years ago, they have been struggling with a chicken/egg conundrum: Which came first, the small hippocampus or the traumatic event that led to the trauma disorder?

Scientists aren't sure what is causing the shrinkage in that particular part of the brain. PTSD researchers at BYU and elsewhere say it might be a sudden oversupply of neurotransmitters that adversely affect the tissue.

Chemical changes, such as stress hormones, induced by injury might prevent regeneration of the cells in the hippocampus.

More accurate tracking of the deterioration is possible with brain scans. But they're not practical because almost all are done after an injury. Few are done prior because they're too expensive to be included as a part of regular preventive medical care.

Hedges and grad student Martin Woon did what they could to get around that problem by dividing their study population into two groups — abused children with PTSD and adults with PTSD stemming from childhood abuse.

Data was also combined with the findings from 19 previously published studies where magnetic brain images were obtained from people who had experienced childhood trauma.

The which-comes-first question remains, but the BYU team found "children's hippocampi were intact after the onset of abuse, but somehow there was shrinkage in the group that had reached adulthood."