A study on the survivors of the massive 1988 earthquake that killed 17,000 people in Armenia, and destroyed nearly half the town of Gumri, has revealed that vulnerability to post-traumatic stress disorder, depression and anxiety may be inherited through genes.
Armen Goenjian, a research psychiatrist in the Department of Psychiatry and Biobehavioral Sciences at the University of California, Los Angeles, studied 200 participants from 12 multigenerational families exposed to the earthquake.
The researcher revealed that the subjects suffered from varying degrees of the disorders.
Reporting their findings in the journal Psychiatric Genetics, he and his colleagues revealed that 41 percent of the variation of PTSD symptoms was due to genetic factors.
They also said that 61 percent of the variation of depressive symptoms and 66 percent of anxiety symptoms were attributable to genetics.
The team added that they found that a large proportion of the genetic liabilities for the disorders were shared.
"This was a study of multigenerational family members - parents and offspring, grandparents and grandchildren, siblings, and so on - and we found that the genetic makeup of some of these individuals renders them more vulnerable to develop PTSD, anxiety and depressive symptoms," said Goenjian, a member of the UCLA-Duke University National Center for Child Traumatic Stress and lead author of the study.
According to him, the study suggests that a large percentage of genes are shared between the disorders.
"That tracks with clinical experience. For example, in clinical practice, the therapist will often discover that patients who come in for treatment of depression have coexisting anxiety. Our findings show that a substantial portion of the coexistence can be explained on the basis of shared genes and not just environmental factors such as upbringing," he said.
The study involving statistical methods to assess heritabilities showed that that a significant amount of genes were shared between PTSD and depression, PTSD and anxiety, and finally depression and anxiety.
Goenjian claimed that this is the first time that a study suggesting such a heritability of PTSD has been based on whole families, who were exposed to a particular trauma like earthquake.
He said all previous studies showing such results had been twin studies.
"It's very hard to do family studies on PTSD because typically only single individuals, not whole families, are exposed to a particular trauma. In our study, we were able to avert this problem since all the subjects were exposed to the same severe trauma at the same time," he said.
Goenjian said that the findings were promising for the next step in understanding the underlying biology of such disorders, that is, locating the specific genes involved.