Lifetime adversity tends to sensitize the brain, making it more vulnerable to developing symptoms of post-traumatic stress disorder (PTSD) when later trauma is experienced, according to a new Austrian study published in the journal Biological Psychiatry: Cognitive Neuroscience and Neuroimaging.
The findings could help explain why some people are more vulnerable to the effects of traumatic experiences while others seem resilient.
“Understanding why some people develop intrusive thoughts of a stressful or traumatic event and others do not is an important step towards preventing and treating posttraumatic stress disorder,” said Cameron Carter, M.D., editor of the journal.
The results suggest that when a person has experienced numerous adversities in their lifetime, it increases neural processing during a later traumatic event. These factors combine to increase the frequency of intrusive traumatic memories and the distress they cause. This increased neural processing was found in brain regions important for emotion and memory.
“This suggests that both previous experience and the level of neural activity in the brain during an event interact to determine whether a person will have subsequent trauma-related symptoms following a traumatic experience,” said Carter.
Due to the nature of real-life trauma, which occurs randomly and encompasses many different types of adversity, it is impossible to study how neural processing during natural events contributes to PTSD.
Using functional magnetic resonance imaging (fMRI) and experimental trauma, researchers at the University of Salzburg in Austria conducted the first study of two well-known risk factors of PTSD: neural processing and lifetime adversity. After watching disturbing films of severe interpersonal violence, the participants reported how often they experienced intrusive memories of the films, and how distressing these memories were.
“This allowed us to study how the brain deals with intensely emotional events,” said lead author Julina Rattel, M.Sc., a doctoral student in the laboratory of senior author Frank Wilhelm, Ph.D.
“We found that increased brain activation in specific neural networks implicated in threat processing, emotion regulation, and memory encoding and consolidation predicted distressing recollections; though, this was only the case in individuals reporting several lifetime adversities, such as car accidents, assault, physical and sexual abuse, or natural disaster.”
Both neural processing and lifetime adversity have been considered risk factors for PTSD, but the study is the first to investigate the individual effects of each of these factors, and how they interact synergistically.
“It has long been known that repeated ‘hits’ increase vulnerability to develop PTSD. Our results point to specific vulnerable brain networks that appear to have been sensitized by these hits, subsequently leading to PTSD-like symptoms when reactivated,” said Rattel.