© iStockPhotoPhysical and chemical changes in the brain caused by abuse early in life can be passed down from mother to child, studies sho
The review of published research by behavioral scientists at Emory University in Atlanta was based on studies that show how early life stress (ELS), such as physical and emotional abuse and neglect, leads to observable changes in the brain's hypothalamic-pituitary-adrenal (HPA) axis.
This system, which is responsible for controlling the "fight or flight" response in humans, can be physically altered by abuse.
While these changes can happen when abuse occurs at any point in life, the Emory study shows that abuse during pre-teen and adolescent years are most damaging, resulting in mood and anxiety disorders like Post Traumatic Stress Disorder (PTSD) and depression.
What's more, the functional and physical changes caused by ELS can be passed along from female victims to their children. One of these means of transmission is through epigenetic changes.
Epigenetics is a new field of study that examines how the function of DNA can change without any change to the DNA sequence itself. Through a process known as methylation, protein tags that enhance or thwart the function of a gene can be attached to an individual's DNA.
Even after a cell divides, the DNA can still carry the new tags"
This means that once a methyl mark has been placed on the DNA, it may be passed along to subsequent generations," said Cynthia Wolberger, an epigenetics specialist at Johns Hopkins Medical Institute, who is unaffiliated with the Emory Study.
Wolberger said that DNA methylation can be caused by a number of things, including stress. Since epigenetic changes can be brought on by stresses like abuse and those changes can be passed from mother to child, the symptoms of early abuse can be passed along years later from the original victim to her child -- even if the child has never been exposed to any traumatic stresses.
Gretchen Neigh, a senior author of the Emory study, said the clearest evidence of transmission of HPA axis alterations was seen in expectant mothers who suffer a mood disorder from an early life stress or who are abused during pregnancy.
"That's the worst case scenario," Neigh said.
In addition to showing that brain dysfunction can be transmitted from mother to offspring epigenetically, studies using rodent models have proven these changes can be passed along both before and after giving birth.
Mothers with a history of early life stress are less attentive to their offspring; during pregnancy, cortisol can seep through the placenta, directly exposing the fetus to a flood of the stress hormone. Each of these scenarios can cause the newborn's brain's fight-or-flight response to malfunction.
Neigh believes her team's research should inform policy-makers about the challenges that abused children face.
"Research has shown that early intervention can reverse the effects of (early life stress)," she told Discovery News. "Anything we can do to prevent it from happening or get them back on track as soon as possible will help address the problem."
The study was published in the October issue of the journal Trauma, Violence, & Abuse.
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