Susceptibility to others' emotions moderates immediate self-reported and biological stress responses to witnessing trauma.

•The stress response to witnessed trauma might depend on the susceptibility to others' emotions.•We tested this hypothesis in an analogue study using a trauma film paradigm.•Individuals with high susceptibility to others' negative emotions rated the trauma film more stressful.•Susceptibility to others' negative emotions was also related to increased self-reported anxiety and heart rate.•Susceptibility to others' positive emotions was not related to measures of stress reactivity.