Terrifying flashbacks from post-traumatic stress disorder (PTSD) may be partially genetic, a new study of more than 165,000 US veterans suggests.
Scientists from two Veteran Affairs hospitals, Yale University and the University of California, San Diego found eight DNA regions common to many white male soldiers who re-live their traumatic experiences.
Black and female soldiers didn’t seem to share these genes, but this may simply have been a statistical issue because comparatively few were involved in the study, the authors say.
Between 11 and 20 percent of American soldiers who served in Iraq suffered PTSD – and finding its DNA underpinnings could help predict who is at risk of developing the debilitating condition and how to treat those who do.
Between eight and 12 percent of US veterans develop PTSD – and a new study identifies eight genetic risk factors that may increase the odds that people relive the traumatic events
More than half of American adults experience at least one traumatic event in their lifetimes.
Trauma can come in the form of a car crash, a sudden loss or violence, to name a few sources.
People in certain lines of work, such has health care, are at greater risk for experiencing trauma, but perhaps none so much as combat soldiers, who must put their lives on the line and often witness or are victims of horrific violence in the line of duty.
But even so, not all of these people develop PTSD, a debilitating, chronic psychological condition.
PTSD is marked by symptoms similar to those of anxiety, such as irritability, trouble sleeping, jumpiness, volatility, becoming withdrawn and generally operating in a sort of fight-or-flight mode.
But PTSD sufferers also relive their trauma, a unique and particularly distressing symptom of the condition that functions as a key diagnostic marker for it.
It isn’t clear why some people develop PTSD and are jerked back into the throes of their trauma and others don’t.
A great deal of research has attempted to identify genetic markers for the disorder, but doing so is a difficult task because of its shared symptoms – and therefore, possible shared DNA – with other psychiatric disorders.
So scientists at VAs in Connecticut and San Diego as well as UCSD and Vanderbilt decided to hone in on the genes of just those veterans who had PTSD and reported flashbacks.
They compared diagnoses and symptoms to DNA samples from 166,643 US veterans.
White veterans – who made up the vast majority of the sample, with 146,660 participants – who re-experienced trauma as part of their PTSD commonly shared variations in eight locations in their genomes.
Of those eight locations, three had particularly strong associations with flashback-like symptoms, according to the study, published today in Nature Neuroscience.
More importantly, the genes they identified in the PTSD-suffering veterans followed two patterns.
Some of the genes were linked to cortisol, the stress hormone.
Scientists know that cortisol plays an important role in PTSD, but it isn’t yet clear how the genetic variations alter cortisol production or responses in people at risk for the disorder.
‘The body has certain ways to kick into gear when there’s a stressful situation, and part of that is the cortisol response,’ study co-author and Yale psychiatrist Dr Spencer Gelernter told DailyMail.com.
The second pattern showed interesting ties to different psychiatric disorders that might be useful in working out how to treat different individuals’ PTSD.
A common gene variant in the veterans with PTSD has also been linked to schizophrenia, and conditions like bipolar disorder, which may come with psychotic episodes.
‘Medications that have been used to treat schizophrenia – anti-psychotics – have been attempted in some patients who have PTSD and, so far, the results have been negative or, the best we can say, is inconclusive,’ explains Dr Gelernter.
When someone with PTSD re-experiences a traumatic event, they are feeling as though it’s happening all over again – but they know that they’re really just caught up in a vivid, painful memory.
People who are schizophrenic or having a psychotic episode, however, lack this awareness. The strange event seems to them to be new and external when, in reality, it is most likely traceable to their own experiences too.
Dr Gelernter and his team hypothesize that ‘the main difference is awareness in PTSD and lack of awareness in schizophrenia, so these risk genes may be related to re-experience,’ he says.
With a better understanding of genetic risk factors for both schizophrenia and PTSD flashbacks – and the tie between the two – doctors might be able to better pinpoint which PTSD patients might benefit from these drugs, even if they are not schizophrenic.
This, of course, still needs to be tested, but it’s a step toward using the understanding of genetic risk that scientists glean from large data sets like the US Million Veteran Program’s biobank of genetic data in a clinical setting.
‘We are fascinated by the genetics of this disorder but, ultimately, our goal is to make better treatment for patients that have that problem,’ said Dr Gelernter.
‘And we see some way that we could lean in that direction with these results.’