Trauma experiences change the brain even in those without PTSD

Trauma may cause distinct and long-lasting effects even in people who do not develop PTSD (post-traumatic stress disorder), according to research by scientists working at the University of Oxford's Department of Psychiatry. It is already known that stress affects brain function and may lead to PTSD, but until now the underlying brain networks have proven elusive.

Led by Prof Morten Kringelbach, the Oxford team's systematic meta-analysis of all brain research on PTSD is published in the journal Neuroscience and Biobehavioural Reviews. The research is part of a larger programme on PTSD in British war veterans run by the Scars of War Foundation based at The Queen's College, University of Oxford. The foundation uses neuroscience to advance understanding of the effects of war and disaster.

The research team's initial survey of the scientific literature for all the published studies reporting brain activity in individuals with a diagnosis of PTSD yielded over 2000 records. This number was then reduced using stringent criteria to ensure the highest possible data quality for processing with meta-analytic tools.

The team separated studies by type of control group: trauma-exposed (those who had experienced trauma but did not have a diagnosis of PTSD) and trauma-naïve (those who had not experienced trauma), and compared the individuals with PTSD to both groups. This yielded an insight into how the abnormalities in functional brain activity in PTSD comprise a whole-brain network.

The analysis showed that there were differences between the brain activity of individuals with PTSD and that of the groups of both trauma-exposed and trauma-naïve participants.

This suggests that even in the absence of symptoms, trauma may have an enduring effect on brain function. Critically, the research found that in parts of a region of the brain called the basal ganglia, brain activity was different when comparing people with PTSD to the trauma-exposed group.

The findings suggest that the transition to clinical PTSD could be linked with imbalances specifically in the basal ganglia - but linked with imbalances in a larger brain network. This view has been reinforced by new evidence uncovered by the team using whole-brain computational modelling of other neuropsychiatric disorders. This modelling showed that these disorders lead to specific imbalances in specific brain networks.

Crucially, the meta-analysis has identified the need to directly compare trauma-exposed and trauma-naïve groups to identify potential biomarkers that could help early diagnosis and potentially novel treatments for PTSD.

Professor Kringelbach said: 'This research suggests that there may be a spectrum of traumatic effect on the brain, where people who have experienced trauma may not meet the threshold for a diagnosis of PTSD but may have similar changes within the brain. This could make them more susceptible to PTSD if they experience a subsequent trauma.