Severe stress can affect children's brain development, according to U.S. researchers.

Children with post-traumatic stress disorder and high levels of the stress hormone cortisol were likely to experience a decrease in the size of the hippocampus, a brain structure important in memory processing and emotion, said researchers at the Stanford University School of Medicine and Lucile Packard Children's Hospital

The children in the study were suffering from post-traumatic stress disorder, or PTSD, as a result of undergoing physical, emotional or sexual abuse, witnessing violence or experiencing lasting separation and loss. This type of developmental trauma often impairs the child's ability to reach social, emotional and academic milestones.

The researchers studied 15 children from age 7 to 13 suffering from PTSD. They measured the volume of the hippocampus at the beginning and end of the 12- to 18-month study period.

After correcting for gender and for physiological maturity, they found that kids with more severe PTSD symptoms and higher bedtime cortisol levels (another marker of stress) at the start of the study were more likely to have reductions in their hippocampal volumes at the end of the study than their less-affected, but still traumatized peers.

"We know, for example, that these children are at higher risk of developing depression and/or anxiety as adults," said child psychiatrist Victor Carrion.

Carrion, assistant professor of child and adolescent psychiatry at the medical school and director of Stanford's early life stress research program speculated that cognitive deficits arising from stress hormones interfere with psychiatric therapy and prolong symptoms.

"We'd really like to understand why some children are more resilient than others, and what the long-term effects of extreme stress are," said Carrion.

Children predisposed by genetics or environment to be more anxious than their peers are also more likely to develop PTSD in response to emotional trauma, perhaps because their responses to other life experiences simply left them closer to that threshold than less-anxious children, according to the study to be published in the March issue of Pediatrics.

Although similar effects have been seen in animal studies, this is the first time the findings have been replicated in children.

Source: Xinhua