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The Biological Effects Of Traumatic Events

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We often think of PTSD as a psychological disorder — one that causes great suffering to people who have experienced traumatic events. Now, the lead author of a new study argues that those traumatic events may actually cause changes in the victim on a molecular level. Host Guy Raz speaks with Dr. Sandro Galea of Columbia University about the study.

GUY RAZ, host:

We usually think of PTSD as a psychological disorder, one that can tear apart the lives of combat veterans and other people who've experienced traumatic events. But a new study suggests that those traumatic events may actually change people on a molecular level, and it could be those molecular changes that lead to the symptoms of PTSD.

Sandro Galea is the senior author of the study. He's also the chair of the Department of Epidemiology at Columbia University. Welcome to the program.

Dr. SANDRO GALEA (Chairman, Department of Epidemiology, Columbia University): Thank you for having me on.

RAZ: Your study sort of seems to suggest a completely new biological framework for PTSD, something that we've long - sort of associated with a psychological condition. Describe how it works now, how you think it works.

Dr. GALEA: What we are thinking is that trauma that somebody experiences results in molecular changes around the DNA that result in changes in what genes are expressed and not expressed. So what our study showed is that people who experience traumatic events are more likely to have these molecular epigenetic changes, which may explain in part why particular genes then are expressed or not expressed, and result in symptoms of the psychological disorder.

RAZ: You describe epigenetic changes. Briefly, can you explain what that means?

Dr. GALEA: The term epigenetic changes refers to particular molecules that stick to particular parts of the DNA. So they're not genetic changes, they're not changes in the gene encoding that we all have within us, but they are changes around the DNA.

So an example would be that one of the cardinal symptoms of post-traumatic stress disorder is hypervigilance - being very jumpy, constantly on guard. And we found that some of the genes that we know are responsible for vigilance, for jumpiness, are among the genes that have these epigenetic changes associated with the traumatic event experience.

RAZ: How can you know if these molecular differences between people with and without PTSD cause the disorder, rather than result from the disorder?

Dr. GALEA: It's a challenge to tease apart whether these molecular changes are -cause the disorder or are the result of the disorder. We have a number of analyses in the paper that show, for example, that the more traumatic events people experience, the more of these molecular changes they have. That, of course, suggests that the molecular changes are a result of the traumatic events, not the other way around.

RAZ: Sandro Galea, what do you think all of this research could mean for the way post-traumatic stress disorder might be understood, and also treated in the future?

Dr. GALEA: The closest we are to is to think of these molecular changes as a marker of PTSD. And it is far from here to treatment. But at the same time, understanding how it is that PTSD comes about is what ultimately will lead to better therapeutic interventions.

RAZ: Sandro Galea's study on the biology of PTSD was published online this week in the "Proceedings of the National Academy of Sciences." He joined us from Columbia University. Sandro Galea, thank you so much.

Dr. GALEA: Thank you very much for having me.

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