A particular genetic variant makes people much more susceptible to PTSD after tragic experiences, but only if they have also had an abusive childhood, scientists in the United States have discovered.
PTSD is a serious anxiety disorder that develops among people who experience unpleasant events, such as war, murders, terrorist attacks or natural disasters. It leads to nightmares, insomnia, flashbacks, mood swings and depression, and can severely impair the ability to live a normal life.
The study, led by a team at Emory University, looked at 900 adults, most of them low-income and African-American, seeking medical care at two clinics in Atlanta. A history of trauma is common in poor, urban populations.
Researchers found that 80 percent of the subjects had been exposed to trauma, with the great majority exposed to multiple traumatic stressors in their lives. About 30 percent had been abused as children, which is a major risk factor for developing PTSD.
When the subjects were evaluated with a psychiatric questionnaire for symptoms of PTSD, 25 percent met the criteria for the disorder. The research team collected saliva samples from each subject and looked at a gene known as FKBP5, which influences the body's response to the stress-related hormone cortisol.
Researchers concluded that each of us have slightly different versions of this gene but four variants of the gene were associated with an increased rate of PTSD in individuals who also had a history of child abuse. Other variants seemed to confer some protection or resilience.
PTSD has prevalence rates of at least 7 percent to 8 percent in the U.S. population, and with much higher rates among combat veterans and those living in high-violence areas.
The results, which are published in the Journal of the American Medical Association, follow other studies that have shown how genetic variants interact with environmental factors to affect behaviour or mental health.
