Bright Mind Focuses On Identifying the Risk Factors and Biological Roots of PTSD

From The Quarterly, Summer 2014

Kerry Ressler, M.D., Ph.D., is one of America’s leading authorities on the psychological and behavioral impacts of trauma––not just trauma suffered by soldiers on the battlefield but also by civilians, here at home. “Post-traumatic stress disorder,” or PTSD, was first coined as a term after the Vietnam War and acknowledged as an illness when it was added to the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) in 1980.

“The first thing people should know about PTSD is that it happens after a trauma, and is caused by unwanted intrusions of terrifying memories into our conscious thoughts and even our dreams,” says Dr. Ressler. ”It can happen to anybody, yet some people are more prone to it than others, and our research is beginning to explain who is more at risk. A second thing we know about PTSD is that the more trauma you have experienced, the more at-risk you are. So, multiple battlefield deployments like we saw in the Iraq war definitely put people at greater risk. But this applies just as much to sources of risk found in our own cities, especially the most violent inner cities. In Atlanta, we see rates of PTSD as high as those seen in Vietnam vets.”

Dr. Ressler is Co-Director of the Grady Trauma Project, based at Atlanta’s Grady Hospital, whose aim is to better understand the specific risks of post-traumatic injury in places where violence in the streets and within families (in the form of sexual abuse, spousal and child battery and abandonment, for example) is far above average. “Almost half of the 8,000 people we’ve interviewed in Atlanta know someone who has been murdered. Two-thirds have been attacked. One- third has been sexually assaulted.”

In a 2012 paper suggesting the value of early intervention, Dr. Ressler and colleagues said that while “most people will experience symptoms of post-traumatic stress in the immediate aftermath of a trauma, these reactions typically extinguish over time.” What’s perplexing is why some people can purge these memories and others cannot. Aside from having unwanted traumatic memories, those who suffer from PTSD often avoid places or people associated with the trauma, have an overly sensitive startle response (called hyper-arousal), are emotionally numb and tend to have angry outbursts.

In the first years of the Grady Trauma Project, Dr. Ressler realized that in Atlanta he was “well equipped to study resilience. We interview people who have had an enormous amount of lifetime trauma and we see that they are reasonably happy, able to hold a job, trying their best to be a good parent, getting on with life with very few symptoms.”

This, he says, is “the flip side” of seeing very high rates of PTSD in violent inner-city neighborhoods: “We actually see more people who don’t have PTSD or depression (which often co-occurs with it), people who have every reason in the world to be overwhelmed.”

Doctors know that childhood trauma or abuse is the biggest risk factor for developing PTSD. In fact, someone who experiences trauma as a child is more at risk for adult PTSD than an adult who experiences trauma. The impact for those who happen to be vulnerable extends far into the future. But why? And, in biological terms, who and how?

Here is where research is answering key questions that should lead to better therapies. “Until quite recently,” says Dr. Ressler, “an expert would say that PTSD was about the trauma exposure itself,” and not about a person’s biological make-up. But studies in identical twins now suggest that 30 to 40 percent of a person’s risk for developing PTSD is genetic.

Very little is known about gene variations that increase a person’s PTSD risk. By studying the fear response in rodents, Dr. Ressler and others in the field have made some progress in identifying specific mutations. But the evidence won’t be persuasive until much larger population samples are analyzed.

Other PTSD studies by Dr. Ressler and colleagues have yielded many new insights. In the last three years alone they have made a number of important findings:

• Different versions (polymorphisms) of genes associated with the fear and stress response in mice are also associated with abnormalities in the human brain’s amygdala and hippocampus—an increased reaction to threat stimuli and a decrease in connectivity between the two regions. These two brain areas are central to memory, the fear response and learning.
• In adults who were abused as children, those resilient to stress and trauma are less likely to misuse alcohol and drugs.
• PTSD may function “as a pathway” between childhood abuse exposure and development of pain related conditions in adulthood.
• Childhood trauma exposure may contribute to increased risk of heart disease through its influence on lipid levels, in males but curiously not in females.
• Estrogen may contribute to differential PTSD vulnerability for women with trauma histories.