PTSD symptoms linked to the tendency to absorb others’ stress reactions

A new study published in Translational Psychiatry has found that individuals exposed to war-related trauma who experience a strong physiological and emotional response when observing others in distress may be more likely to report symptoms of post-traumatic stress disorder. The findings suggest that the tendency to resonate with others’ stress—through elevated heart rate, subjective stress, and other physiological responses—may not necessarily increase vulnerability to PTSD, but may instead reflect the presence of PTSD symptoms themselves.

Post-traumatic stress disorder (PTSD) is a mental health condition that can develop after exposure to a traumatic event, such as war, violence, or forced displacement. It often involves persistent symptoms like hyperarousal, intrusive memories, emotional detachment, and disrupted sleep. Refugees and migrants who have experienced war or persecution are at particularly high risk for developing PTSD, given both the trauma they endured and the continued stress they face in the process of resettlement.

While not all individuals exposed to trauma develop PTSD, researchers have been working to identify factors that influence who is more likely to struggle with long-term psychological effects. One emerging area of interest is the idea of “stress resonance,” or the extent to which someone shares in another person’s emotional or physiological stress.

This resonance, closely related to empathy, occurs when observing another person in distress triggers similar responses in the observer’s own body and emotions. While empathy can promote connection and cooperation in social settings, some researchers have hypothesized that it could become harmful when it leads to heightened and repeated internal stress responses.

The new study explored whether heightened stress resonance could act as a vulnerability factor for PTSD, or whether it might instead be a byproduct of the disorder. The researchers focused on refugees and migrants from Arabic-speaking countries who had resettled in Germany, aiming to test whether individuals who responded more strongly to another person’s stress were more likely to experience PTSD symptoms.

“The study was based on the idea that people differ in how much empathy they feel, and these differences may affect whether someone is more vulnerable or more resilient when facing war-related trauma,” said study author Christiane Wesarg-Menzel of the Max Planck Institute for Human Cognitive and Brain Sciences and Friedrich-Schiller University.

The study included 67 adult participants from Arabic-speaking countries, some of whom had entered Germany as refugees and others as migrants. Refugees had fled war, violence, or persecution, while migrants had relocated for reasons such as work or study and reported no major trauma exposure. All participants observed a German-speaking individual undergo a standardized laboratory stress test known to trigger physiological and emotional stress.

During this procedure, participants observed the stressed person through a one-way mirror as they completed tasks designed to induce social-evaluative stress, such as a mock job interview and a challenging mental arithmetic task in front of an evaluative panel. Throughout the process, researchers measured multiple indicators of stress in both the person undergoing the test and the observers. These included heart rate, heart rate variability, salivary cortisol levels, and self-reported stress ratings.

The goal was to assess whether the observers’ responses matched the stress levels of the person being watched. This degree of synchronization—termed stress resonance—was calculated by comparing changes in physiological and emotional markers between the observer and the person undergoing stress. The researchers then looked at how these resonance scores related to each participant’s reported level of PTSD symptoms, measured through a validated questionnaire.

The researchers initially hypothesized that stress resonance would increase the link between trauma exposure and PTSD symptoms, suggesting it might be a trait that makes some individuals more vulnerable. However, the results did not support this idea. Instead, the analysis indicated that higher levels of stress resonance were directly associated with higher PTSD symptom severity, even when taking trauma exposure, age, and sex into account.

“We started off with the hypothesis that people who strongly ‘pick up’ on the stress of others would be more vulnerable to developing mental health problems than those who resonate less, even if both had gone through similar traumatic experiences,” Wesarg-Menzel told PsyPost. “However, our data did not support this idea. Instead, we found that individuals reporting more severe PTSD symptoms resonated more with a stranger under stress. This was visible not only in how stressed they said they felt, but also in their heart rate and heart rate variability.”

In particular, greater alignment in subjective stress, heart rate, and heart rate variability between the observer and the stressed individual was linked to more severe PTSD symptoms. Cortisol-based stress resonance, on the other hand, did not show a significant association. The authors interpret this pattern as suggesting that heightened stress resonance may be better understood as a correlate—or possible symptom—of PTSD, rather than a pre-existing risk factor.

Additional findings revealed that some participants exhibited such strong physiological responses while observing the stress test that their stress levels surpassed those of the individuals actually undergoing the test. This phenomenon was observed in both refugees and migrants, with no significant group differences in stress resonance across physiological markers.

The researchers also found that stress resonance was modestly related to self-reported personal distress, a trait-level measure of empathy characterized by discomfort or anxiety in response to others’ suffering. This connection adds weight to the idea that emotional sensitivity to others’ stress may play a role in how PTSD symptoms manifest.

Importantly, the researchers note that while trauma exposure was strongly related to PTSD symptoms, it was not linked to the degree of stress resonance. This suggests that the observed resonance effects were not merely a byproduct of trauma history alone, but rather tied more specifically to current psychological symptoms.

“Refugees and migrants from Arabic-speaking countries have often been exposed to many traumatic experiences, which puts them at higher risk of developing mental health problems,” Wesarg-Menzel said. “In our study, we found that people who reported more symptoms of PTSD resonated more with a stranger undergoing a stress test. This means that their heart rate and feelings of stress rose in ways that closely mirrored the stranger’s reactions. We believe this heightened tendency to ‘take on’ another person’s stress may be a symptom of PTSD.”

There are some limitations. The cross-sectional nature of the study limits the ability to draw conclusions about causality. It remains unclear whether heightened stress resonance precedes the development of PTSD symptoms or whether it is a result of them. It is also possible that both emerge together in the aftermath of trauma. Longitudinal studies are needed to trace how stress resonance and PTSD symptoms evolve over time.

The researchers aim to extend their work by examining how empathy influences mental health in adolescent refugees, with a particular focus on the roles that parents and peers may play.

“We want to expand this research into the family context,” Wesarg-Menzel said. “We are currently applying for funding to study how the empathic abilities of adolescent refugees affect their health after displacement, and how parents and peers can support their resilience. Our long-term goal is to help develop interventions that strengthen the mental health of refugees.”

“I would like to once again thank our participants for taking part in the study, our Arabic-speaking student assistants for their support and valuable advices during data collection, and Beyond Conflict and the Max-Planck-Institute for Human Cognitive and Brain Sciences, Leipzig, for funding.”

The study, “Adding to the burden: the tendency to resonate with others’ stress is linked to higher PTSD symptom severity in individuals with war-related trauma,” was authored by Christiane Wesarg-Menzel, Mathilde Gallistl, Michael Niconchuk, and Veronika Engert.