The Grapevine

Genes May Influence PTSD Risk: Biomarkers Connected With Immune System Found

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Genetic analysis of blood led to the identification of biomarkers linked to PTSD, suggesting a test to predict those most vulnerable to this psychiatric disorder is on the horizon. Kevin Dooley, CC by 2.0

Many people find it difficult to understand certain psychological conditions, since there’s no biological "proof" involved. As science and technology advance, though, researchers are developing a molecular understanding of the body while also finding ways to measure the most intricate and subtle differences among us. Now, a new study makes good use of the most recent scientific advancements to gain a deeper understanding of post-traumatic stress disorder (PTSD). Genetic analysis of blood helped a team of researchers identify biomarkers linked to PTSD, suggesting soon a test may predict those most susceptible to this disorder.

While any psychiatric condition is difficult to study, PTSD is even more so because it requires a very specific trigger: a traumatic experience. PTSD occurs after a person experiences a terror, whether that be a natural disaster, a physical assault, a car accident, an explosion, military combat, or similar frights. All or any of these may trigger the common symptoms of the disorder:

  • re-experience (a feeling that the trauma is recurring)
  • avoidance (a strong impulse to avoid anything that has to do with the traumatic experience)
  • hyper-arousal (constant feelings of alertness, nervousness, and difficulty concentrating)

Why exactly do these symptoms occur? Witnessing or experiencing some terrifying event, our natural “fight or flight” response — this is actually just a sudden flood of stress hormones — incapacitates certain areas of our brains. With normal function disabled, our brains are unable to process the experience in the usual way. Lodged in our minds in an unusual way, the trauma randomly returns on occasion, not as a mere memory, but as life re-lived.

Overly Expressive

PTSD, then, is an inescapable return of a past fear. Strangely, though, only some people are susceptible to this disorder. Two soldiers, for instance, fighting side by side may endure the exact same battle, yet only one of them will later develop PTSD. The underlying reasons why PTSD only affects some soldiers has remained a mystery... until now.

For the current study, a team of UC San Diego researchers and their colleagues enlisted the help of 188 United States marines. They took blood samples prior to and after the marines’ deployment to conflict zones. Then, the researchers analyzed both sets of blood using various techniques, including RNA sequencing, and compared the results to psychological profiles of each marine in order to see what connections they might find.

They identified genetic markers before and after the development of PTSD. In particular, they discovered a role played by genes involved in interferon signaling and the immune system that might explain, at least partially, why some people develop PTSD. An "overexpression" of certain immune system genes indicates vulnerability; "overexpression" means that some genes are producing too many proteins — essentially working too hard — and this chemical imbalance on the molecular level creates the necessary pre-condition for development of PTSD.

Importantly, the researchers were able to replicate these results in a second study of 96 U.S. Marines. Many questions remain, including what's stimulating an immune response prior to PTSD development? The researchers believe the answer could be as simple as increased stress prior to deployment ...or as complex as some marines have a higher viral load.

No matter, these findings still advance the science of PTSD, which should prompt improvements in treatment, while helping doctors predict those most susceptible to developing the condition.

Source: Breen MS, Maihofer AX, Glatt SJ, et al. Gene networks specific for innate immunity define post-traumatic stress disorder. Molecular Psychiatry. 2015.

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