The findings could help scientific understanding of PTSD risk factors (Picture: Crown Copyright).
Genetic factors may expose some people to a higher risk of being haunted by traumatic events, a study suggests.
Researchers found multiple regions in the human genome related to the "re-experiencing" flashback-type symptom of post-traumatic stress disorder (PTSD).
The study comprised of more than 165,000 US military veterans.
The research also identified some genetic overlap between PTSD and other conditions like schizophrenia and bipolar disorder.
This suggests schizophrenia-induced hallucinations may share biochemical pathways with the nightmares and intrusive thoughts of PTSD.
Researchers discovered eight separate regions in the veterans' genome linked with "re-experiencing symptoms" like intrusive thoughts and nightmares.
A variant on a specific gene, CRHR1, seems to suggest that genes which are related to the body's response to stress could be linked to the risk of experiencing PTSD.
The findings could help scientific understanding of PTSD risk factors and inform the development of new drug treatments for the disorder.
The study was carried out by the Yale University School of Medicine, University of California San Diego, and the VA Connecticut and San Diego healthcare systems.
Results were replicated using the UK Biobank sample, which contains the health data of 500,000 volunteers.
Comparisons among 19,983 black veterans, considered as a separate group as there were fewer study participants available, found "no significant associations" with re-experiencing symptoms.
The findings are published in the journal Nature Neuroscience.
PTSD is a mental disorder that affects people who experience a traumatic event and is a major issue afflicting former soldiers.
Symptoms include re-experiencing the distressing event, avoiding stimulus related to it, and the chronic heightened anxiety known as hyperarousal.
Watch: Hollywood director David Lynch is helping serving military personnel and veterans to overcome stress-related illnesses