![Illustration of brain regions studied in mental illness: ACC, amygdala, hippocampus, prefrontal cortex. [NIH]](https://sp-ao.shortpixel.ai/client/to_webp,q_glossy,ret_img,w_750,h_375/https://www.psypost.org/wp-content/uploads/2015/08/Hippocampus-prefrontal-cortex-amygdala-anterior-cingulate-cortex-by-NIMH-750x375.jpg)
A new study published in Biological Psychiatry suggests that brain activity in specific regions before experiencing a traumatic event may help predict whether an individual will develop post-traumatic stress disorder (PTSD). Researchers found that police recruits who showed greater activation in a part of the amygdala—a brain region involved in processing fear—while anticipating a threat were more likely to develop PTSD symptoms after later experiencing trauma.
PTSD is a mental health condition that can develop after a person experiences or witnesses a traumatic event. While many people recover from trauma over time, some continue to experience distressing symptoms long after the event has passed. PTSD can cause intense flashbacks, nightmares, and intrusive memories that make it feel as though the trauma is happening all over again. People with PTSD may also avoid reminders of the event, struggle with emotional numbness, or experience heightened anxiety and irritability. These symptoms can interfere with daily life, relationships, and work, making PTSD a debilitating condition for those affected.
Not everyone who experiences trauma develops PTSD, and researchers have long sought to understand why some individuals are more vulnerable than others. “In The Netherlands, around 80% of individuals experience something traumatic and around 10% of those individuals develop PTSD symptoms. It is therefore an extreme relevant and timely topic,” said study author Lycia D. de Voogd, an assistant professor at Leiden University.
The brain plays a key role in how people respond to fear and stress, and differences in brain function may help explain variations in PTSD risk. One brain region of particular interest is the amygdala, which is responsible for detecting threats and triggering emotional responses. Studies have shown that people with PTSD often have heightened activity in the amygdala, but it has been unclear whether this overactivity is a result of trauma or a pre-existing vulnerability.
The motivation behind this study was to determine whether differences in brain function before trauma exposure could predict who would later develop PTSD symptoms. Studying PTSD risk is challenging because researchers typically cannot measure brain activity before a traumatic event occurs. To address this, a team of researchers partnered with the Dutch National Police to conduct a large-scale study called Police in Action.
Police officers frequently experience traumatic situations, making them a valuable group for studying PTSD risk. The study examined recruits at the very beginning of their training, before they were exposed to real-world policing situations. By following these recruits over time, the researchers aimed to identify differences in brain activity that might predict who would later develop PTSD symptoms.
The study followed 221 police recruits, tracking their brain activity and PTSD symptoms over a period of about 18 months. At the start of their training, before they had encountered trauma, the recruits underwent a brain scan while completing a task designed to simulate high-stress decision-making. In this task, they watched an avatar in a virtual parking lot. Sometimes, the avatar pulled out a gun, and the recruit had to quickly decide whether to shoot. Other times, the avatar pulled out a harmless object, such as a mobile phone, and the correct choice was not to shoot. If the recruit made the wrong decision—such as shooting an unarmed person—they received an electric shock to their finger.
This task was designed to mimic the split-second decisions police officers must make in the field. Importantly, the brain scan allowed researchers to measure how different parts of the brain responded before the recruits had to act—specifically, while they were anticipating a possible threat.
After approximately 18 months, the researchers followed up with the recruits to assess whether they had experienced traumatic events on duty and whether they had developed PTSD symptoms. This allowed the team to compare brain activity before trauma with PTSD symptoms that developed later.
The study revealed that police recruits who showed higher activity in the dorsal part of the amygdala while anticipating a threat were more likely to develop PTSD symptoms after experiencing trauma. This suggests that heightened sensitivity to potential threats—even before an event occurs—may indicate a greater risk for PTSD.
On the other hand, after experiencing trauma, recruits who had more activation in the lateral part of the amygdala when responding to distressing stimuli seemed to have greater difficulty regulating their emotional responses. This suggests that while some patterns of brain activity may predict PTSD risk before trauma occurs, other changes may be a result of trauma exposure itself.
In addition to amygdala activity, the study found that recruits who later developed PTSD symptoms showed stronger connections between the amygdala and a brain region called the precuneus. The precuneus is involved in self-awareness, memory, and attention, and has been increasingly linked to PTSD risk. This suggests that the way the brain integrates external threats with personal experiences may play a role in how individuals process trauma.
“The main finding is that amygdala activity during threat anticipation predicts the later development of PTSD symptoms after trauma,” de Voogd told PsyPost. “This means that some of us are more sensitive to developing symptoms than others following a traumatic experience.”
The study provides some of the clearest evidence yet that differences in brain activity before a traumatic event can help predict who will later develop PTSD symptoms. If these findings are confirmed in future research, they could pave the way for early identification of individuals at higher risk for PTSD, potentially leading to targeted interventions before symptoms develop.
One possibility is that training programs could be developed to help individuals regulate their amygdala activity, reducing their vulnerability to PTSD. Some studies have already suggested that techniques such as neurofeedback, in which individuals learn to control their own brain activity in real time, may help with emotional regulation. If it becomes possible to “train” the brain to be less reactive to anticipated threats, this could help people cope with trauma more effectively.
However, the study also has limitations. While the findings are based on a relatively large group of police recruits, it is unclear whether the same patterns of brain activity would predict PTSD in the general population or in people exposed to different types of trauma. Additionally, although the study shows a link between amygdala activity and PTSD symptoms, it does not establish a direct cause-and-effect relationship. Further research is needed to confirm these results and explore how brain activity interacts with other factors, such as genetics and personal history.
The research team is now investigating whether training the brain’s defensive systems can help reduce the likelihood of PTSD. By better understanding the neural mechanisms underlying PTSD risk, scientists hope to develop more effective ways to protect individuals from the long-term effects of trauma.
The study, “Amygdala hyperactivity in PTSD: disentangling predisposing from consequential factors in a prospective longitudinal design,” was authored by Lycia D. de Voogd, Mahur M. Hashemi, Wei Zhang, Reinoud Kaldewaij, Saskia B.J. Koch, Vanessa A. van Ast, Floris Klumpers, and Karin Roelofs.
