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.