New research provides evidence that heart rate reactivity is a biological moderator between bullying and internalizing problems in adolescent girls.

The findings, which appear in Evolutionary Psychological Science, could help explain why peer victimization leads to internalizing problems in some girls but not others.

“The theory of Biological Sensitivity to Context is a fascinating one,” said study author Christopher D. Aults, an assistant professor of Psychology at King’s College.

The theory holds that the environment in early life predisposes individuals to have varying degrees of reactivity to stress, which can have both beneficial and societally maladaptive outcomes.

“Understanding how individual differences contribute to psychological adjustment is an important area of research. Peer victimization is rarely used as a variable of interest in these models, so we wanted to explore if victimization interacted with heightened stress reactivity to predict increases in internalizing problems in adolescents,” Aults said.

In the study of 44 girls and 38 boys (11–14 years of age), the researchers monitored the children’s resting heart rate before introducing a laboratory stressor. The difference between the resting heart rate and heart rate in response to the stressor was used as a measure of physiological reactivity.

The researchers found that girls whose heart rates were highly reactive tended to be more likely to have internalizing problems, such as depression and anxiety, when subjected to a higher level of bullying. But girls with high reactivity tended to rank lower on internalizing behaviors when subjected to a low levels of bullying.

“In essence, they are most apt to thrive when supported by peers, but also most likely to struggle when victimized by peers,” the researchers wrote.

Girls with low cardiovascular reactivity, on the other hand, were less impacted by their social environment, whether that environment was positive or negative.

“Studying stress reactivity in adolescents who are victimized by their peers may be a good indicator for predicting internalizing problems, particularly for girls,” Aults told PsyPost.

For boys, cardiovascular reactivity did not appear to have a moderating influence. And the study — like all research — includes some limitations.

“This study was concurrent and correlational. Looking at stress reactivity, or even the severity of victimization over time in a longitudinal fashion, is needed,” Aults said.

The study, “Adolescent Girls’ Biological Sensitivity to Context: Heart Rate Reactivity Moderates the Relationship Between Peer Victimization and Internalizing Problems,” was authored by Christopher D. Aults, Karin Machluf, P. Douglas Sellers II, and Nancy Aaron Jones.