Researchers from UC Berkeley and UCSF have said the results suggest there is a neurological reason for why some people may be more resilient, and others vulnerable to developing the symptoms of PTSD after a traumatic or stressful event.

What is myelin?

Myelin is a substance made up off proteins and fat that essentially insulates axons and neurons, the function of myelin is to strengthen ‘long-distance’ transmission across the brain. For the brain to function and for us to function how it/we need to when it comes to stress responses, there needs to be more myelin in some areas of the brain, and less in others.

In other words, if trauma and stress leads your brain to developing myelin where it is not needed, your brain may inadvertently be strengthening connections that are damaging to you. For example, a traumatic or stressful event might result in your brain creating hyper-connection between a memory and an emotional response, meaning anything that triggers that memory, even if it isn’t actually linked to ‘real world’ danger results in a stressed, traumatised emotional response.

What did the research show?

Researchers at UCSF started with working with 38 veterans, half with diagnosed PTSD and half without, focusing on the difference in their brain structure, meanwhile colleagues over at UC Berkley began observing anxious behaviour in rats who had been exposed to a ‘stressful event’ and their brains.

The team at UCSF found that those veterans with a diagnosis of PTSD had an increase in what the researchers call ‘myelination’ in the gray matter of the brain, simultaneously the team at UC Berkley began to observe those rats who had a trauma response to the stressful event also had increased myelination in areas of the brain that have become synonymous with stress responses.

Key findings:

  • Veterans with PTSD and ‘stressed’ rats showed typical symptoms associated with PTSD such as avoidant behaviour.
  • The increased myelination in veteran’s and rat’s brains had a concentration in the hippocampus where much of our memory is stored.
  • Another area of concentration was in the amygdala which is key in regulating strong emotions such as anger, fear and love.
  • For those suffering from anxiety, the dentate gyrus had increased myelination, this is a brain region thought to be critical in how we store learning in our long-term memory.

Trauma: one size does not fit all

Researchers acknowledge there is an incredibly wide and varied experience of trauma and PTSD among humans and rats. Senior author of the joint UC Berkley and UCSF research, Daniela Kaufer spoke to Neuroscience News saying:

“We understand that there’s a lot of individual variation in humans, but with rats, they’re genetically identical, so you think when you expose them to stress you’re going to get the same response…But the response is extremely variable. They sort of fall into groups, such that some are really resilient, and some are vulnerable. And the ones that are vulnerable are vulnerable in different ways: Some show avoidance behaviour, and some show fear learning problems, and some show startle responses that are exaggerated.”

Dr. Thomas Neylan, also senior author of the research, and director of a specialist PTSD and stress clinic in San Francisco, believes their research provides a possible answer to just how individual the response to trauma is. Neylan said, the typical symptoms of stress and PTSD might actually be due to what areas of the brain are being myelinated due to the stressful or traumatic experience.

“Some people are very avoidant. Some people are very hyperreactive. The idea is that if you can show that these different symptom clusters have different neural circuitry, it might actually lead us closer to subtyping people in a way that we could be more targeted in our treatment.” Said Dr. Thomas Neylan.

This research, published at the end of last year in Transactional Psychiatry, could be a essential learning point in our understanding of how and why people develop trauma disorders.

Ground-breaking findings

The researchers ultimately, have found that acute stress produces more of something called a glial cell, which in turn is the cell that goes onto create myelin. When there is too much myelin in a brain region or around a connection between one region and another, it could create ‘hyperresponsive’ connections. This could be the answer to things like hypervigilance, avoidance behaviour and emotional dysregulation that are experienced by many people with both PTSD and complex PTSD (C-PTSD).

“If experience leads you to start to lay down myelin to strengthen certain connections—let’s say your ability to respond quickly to a fearful stimulus—you can speed up that circuit, but you lose the kind of broader adaptive flexibility that you normally would have with mostly unmyelinated axons and dendrites. People with PTSD become almost like a one-note musician—they really know how to respond to fear. But that enhanced, quick response to fear may diminish their adaptive flexibility for non-fear-type behaviour.” Dr. Neylan said. 

This is positive news for those experiencing the debilitating symptoms of trauma disorders such as PTSD and C-PTSD. If these findings are backed up by more research across other demographics (such as those with PTSD diagnosis who are not veterans, it could be that scanning these areas of the brain becomes part of an integrated and holistic approach to treating trauma in the future.