Researchers have identified a gene variant which increases the risk of post-traumatic stress disorder (PTSD) and head injury associated with Alzheimer’s disease and related dementias (ADRD), according to a study.In a study of people at the US Department of Veterans Affairs (VA), US, researchers first found a greater percentage of ADRD in Veterans with PTSD and in those with traumatic brain injury (TBI), relative to those without. They also found higher rates of ADRD in Veterans who had inherited the ε4 variant.The findings appear in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.The researchers then looked for interactions between the ε4 variant, PTSD, and TBI using a mathematical model.Until now, the medical community has not researched the simultaneous impact of PTSD, TBI, and genetic risk factors in a large cohort.The study, led by Dr. Mark Logue, a statistician in the National Center for PTSD at the Veterans Affairs (VA) Boston Healthcare System, found an increase in risk due to PTSD and TBI in Veterans of European ancestry who inherited the ε4 variant.