The researchers from the University of California examined DNA of Armenians who survived the 1988 earthquake to find out that post-traumatic stress disorder (PTSD) can be partially determined by gene variants.

The scientists found out that people having TPH1 and TPH2 gene variants are likely to have more symptoms of post-traumatic stress disorder, BBC reports.

Two gene variants reduce production of serotonin which affects people’s behavior and mood. Thus, it contributed to development of PTSD symptoms.

The study was conducted by a group of researches led by Dr Armen Goenjian among 200 members of 12 Armenian families.