WASHINGTON (Reuters) - A gene that helps regulate the body's response to stress can make certain people more apt to develop post-traumatic stress disorder than others exposed to similar trauma, researchers said on Tuesday.
PTSD is an anxiety disorder that can appear after a person experiences a terrifying event such as physical abuse, rape, military combat, war, torture, accidents and disasters.
The study involved 900 people, primarily low-income blacks, who sought general medical care at an Atlanta hospital. Many had experienced childhood physical or sexual abuse.
After genetic screening of these people, the researchers focused on a gene called FKBP5, which helps control hormones released in response to stress.
Among the people who had experienced the childhood abuse, those with certain variants of the gene were more likely to develop symptoms of PTSD after a trauma in adulthood. People with other variants were less likely to have such symptoms, even after a trauma in adulthood.
The researchers said that while this study involved people with trauma as civilians, the findings may be applicable to others who may develop PTSD in wartime such as combat troops.
Many U.S. troops returning from the wars in Iraq and Afghanistan, for example, are being diagnosed with PTSD.
"When humans face stressful or traumatic situations like combat or car accidents, our bodies have responses to stress that help prepare us to respond -- the fight, flight or freeze response that helps us keep ourselves safe," Rebekah Bradley of the Emory University School of Medicine in Atlanta, one of the researchers, said in an interview.
"The problem is that when you leave the danger or return from combat -- whatever it is -- you need for the stress system to turn itself down," Bradley added. "This gene plays a role in our body's thermostat for its stress response."
The different variants of the gene appear to either amplify the effect of the trauma or dampen the effect, thus making the person more resilient, Bradley said.
Bradley said pinpointing this gene could help guide the development of new drugs to treat people with PTSD.
People with PTSD may experience flashbacks to the traumatic event, nightmares and sleep problems, emotional numbness, irritability, anger, self-destructive behavior, being easily startled or frightened, and hopelessness.
"By understanding how biology and environment and psychology interact to predict risk for mental illness, we may further improve mental health in the future," added Dr. Kerry Ressler of Emory University, another of the researchers.
The findings appear in an edition of the Journal of the American Medical Association focusing on genetics and health.
Another study found that a gene related to HDL cholesterol -- high density lipoprotein or so-called good cholesterol -- helped determine a person's risk for heart disease.
People with one variant of the gene could have two to four times the risk of a heart attack, stroke or death, according to Stanley Hazen of the Cleveland Clinic.
Another study focused on gene variants associated with a modestly increased risk of fractures and lower levels of bone mineral density in the spine and hip.
Editing by Maggie Fox and Cynthia Osterman