A potential pathway to PTSD

A recent study published in Psychological Medicine suggests that childhood trauma may alter the way children learn to respond to fear, which could contribute to the development of post-traumatic stress disorder (PTSD) in adolescence. The researchers found that children who had experienced trauma showed heightened physiological responses to threatening stimuli during a fear-learning task. This heightened response, in turn, was linked to an increase in PTSD symptoms over time.

Childhood trauma is unfortunately common, with nearly half of all children in the United States experiencing some form of adversity. Such experiences, which include physical and sexual abuse, domestic violence, and community violence, have been linked to a wide range of mental health problems, including depression, anxiety, and PTSD. Given the widespread impact of early trauma, researchers have been working to understand how these experiences contribute to the development of mental health issues, with the ultimate goal of developing interventions to help prevent these problems.

“Prior work has shown that youth who have more traumatic experiences (e.g., abuse, experiences of violence) during childhood show differences in how they respond to fearful stimuli through the process of fear learning, but there has been little prior consensus in the direction of these associations,” said study author Laura Machlin, who conducted the research while a postdoctoral fellow at Harvard University.

“I was interested in leveraging a large longitudinal sample of children with a wide range of early life experiences, including traumatic experiences, to directly address if children who have greater trauma-related experiences, controlling for other experiences, would have differences in how they learn about new fearful stimuli. Additionally, I was interested in if changes in how youth respond to fearful stimuli would be associated with greater risk for psychopathology symptoms over time.”

The study was based on a sample of 215 children between the ages of 10 and 13, all of whom were part of a larger, long-term study. The researchers were particularly interested in children who had experienced varying levels of adversity, including both trauma (such as abuse or exposure to violence) and deprivation (such as neglect or lack of emotional support). The goal was to determine whether trauma and deprivation were linked to changes in fear learning and to track how these changes might relate to the development of mental health issues over time.

At the start of the study, both the children and their parents completed questionnaires and interviews about the children’s experiences of trauma and deprivation, as well as their current mental health symptoms. A few weeks later, the children participated in a fear conditioning task, a widely used psychological test designed to measure how well participants learn to distinguish between threatening and non-threatening stimuli.

In this task, the children were exposed to two different cues: one that was consistently followed by an unpleasant stimulus (a mild shock or loud noise, for example) and one that was not. The children’s physiological responses, specifically their skin conductance (a measure of sweat gland activity often used as an indicator of fear or arousal), were recorded during the task.

Two years after the initial testing, the children’s mental health symptoms were assessed again to see if their fear learning responses had predicted any changes in symptoms of PTSD, anxiety, or externalizing behaviors (such as aggression or rule-breaking).

The study’s results provided important insights into the relationship between childhood trauma, fear learning, and mental health. The researchers found that children who had experienced more trauma showed heightened skin conductance responses to the threatening cue during the fear conditioning task. This means that these children were more physiologically reactive to the stimulus they associated with danger, suggesting an increased sensitivity to potential threats. These heightened responses were not observed in children who had experienced deprivation without trauma, suggesting that trauma, specifically, was driving these changes in fear learning.

The researchers also found that the heightened fear response in these children was linked to an increase in PTSD symptoms over the two-year follow-up period. In other words, children who had experienced more trauma and who showed a stronger physiological response to fear were more likely to develop or worsen PTSD symptoms as they grew older.

Interestingly, the study did not find a similar link between altered fear learning and other types of mental health issues, such as anxiety or externalizing behaviors. This suggests that the changes in fear learning observed in traumatized children may be specifically related to PTSD rather than to psychopathology more generally.

“We found that youth with more trauma-related experiences could more easily differentiate between a fearful stimulus and a safe stimulus while passively learning about these stimuli measured through differences in skin conductance response, which is an indirect measure of the level of arousal caused by stimuli,” Machlin told PsyPost. “This increase in arousal to a new fearful stimulus was associated with greater PTSD symptoms over time in early adolescence in youth with more trauma-related experiences. Overall, this work suggests that differences in how youth learn about new fearful stimuli may be one mechanism through which having more trauma-related experiences in childhood confers risk for PTSD symptoms in youth.”

Though this study offers important new insights, it also comes with a few caveats. First, the sample was not a clinical one, meaning that while the children reported symptoms of PTSD and other mental health issues, they were not formally diagnosed with these conditions. Future research might benefit from looking at children who have been clinically diagnosed with PTSD to see if the findings hold true in more severely affected populations.

“This sample includes children drawn from a longitudinal study who were 10 to 13 years old and is not a clinical sample diagnosed with a specific disorder,” Machlin said. “This work should be replicated in a clinical sample.”

Despite these limitations, the study offers important evidence that altered fear learning may be one pathway through which childhood trauma leads to the development of PTSD. This finding could help inform interventions aimed at reducing trauma-related mental health issues in adolescents.

The study, “Alterations in fear learning as a mechanism linking childhood exposure to violence with PTSD symptoms: a longitudinal study,” was authored by Laura Machlin, Margaret A. Sheridan, Lucy A. Lurie, Steven W. Kasparek, Stephanie Gyuri Kim, Matthew Peverill, John McClellan France, Madeline M. Robertson, Tanja Jovanovic, Liliana J. Lengua, and Katie A. McLaughlin.