Study participants were mostly low-income black adults, aged 40 on average, who sought non-psychiatric health care at a public hospital in Atlanta. They were asked about experiences in childhood and as adults and gave saliva samples that underwent genetic testing.
Almost 30% of the participants reported having been sexually or physically abused as children. Most also had experienced trauma as adults, including rape, attacks with weapons and other violence.
The researchers focused on symptoms of PTSD rather than an actual diagnosis, and found that about 25% had stress symptoms severe enough to meet criteria for the disorder, Ressler said.
Childhood abuse and adult trauma each increased risks for PTSD symptoms in adulthood. But the most severe symptoms occurred in the 30% of child abuse survivors who had variations in the stress gene.
The researchers were not able to determine if the symptoms were reactions to the child abuse or to the more recent trauma — or both, said co-author Rebekah Bradley, also of Emory University.
The study is an important contribution to a growing body of research showing how severe abuse early in life can have profound, lasting effects, said Duke University psychiatry expert John Fairbank, co-director of the Duke and UCLA-run National Center for Child Traumatic Stress. He was not involved in the research.