New research has found that inflammatory responses following stressful events predicts an increase in depressive symptoms in female adolescents. The findings indicate that greater biological reactivity to stressors is associated with vulnerability to depression.

The study has been published in the journal Brain, Behavior, and Immunity.

“We were interested in this topic because so many adolescents struggle with depression,” said study authors Marin Kautz, a clinical psychology doctoral student, and Lauren B. Alloy, a professor of psychology at Temple University and head of the Temple Mood and Cognition Lab.

“If we can find ways of identifying which adolescents are most at risk for developing depression through a deeper understanding of biological, psychological, or social risk factors, we hope that we can provide them with interventions and education before their symptoms begin to interfere with their ability to achieve their goals.”

The researchers examined changes in inflammatory markers in 129 male and female adolescents over the course of approximately one year. The participants completed measures of stressful life events and depressive symptoms, and provided blood samples to for measurements of inflammatory markers.

In line with previous research, Kautz and Alloy found a strong relationship between stressful life events and risk for depressive symptoms. They also found evidence that this relationship depends in part on increased inflammatory activity.

“This study was interested in researching how immune system inflammatory processes contribute to our understanding of the biological mechanisms of depression in adolescence. First, we found that higher frequency of stressful events predicts increases in symptoms of depression,” the researchers told PsyPost.

“Second, adolescents who experienced high levels of inflammatory proteins measured in their blood samples following frequent stressors had later increases in symptoms of depression. Our results indicated that greater levels of some types of biological reactivity following recent stressors is associated with later depression for female, but not male, adolescents in particular. However, further research is needed to understand why this mechanism may be stronger for female teenagers.”

The researchers controlled for a number of factors that could influence inflammatory processes, such as race, gender, substance use, body mass index, and hormonal birth control. They also used a longitudinal design, which helps to establish causality, and were able to examine a diverse sample of adolescents.

“Because depression affects teens from all demographic backgrounds, we were very excited to present results from such a diverse sample comprised of a racially and socioeconomically mixed group of female and male adolescents from a large urban setting. This allows us to feel more confident that these conclusions may be able to be extended to the broader population of adolescents in America,” Kautz and Alloy said.

But like all research, the study includes some limitations.

“A major limitation of the study is that the inflammatory biomarkers were measured at only two time points, which gives us only a small snapshot of how inflammation changes during adolescence. Additionally, we did not assess change in the patterns of stressful events over time, which prevents us from making more definitive claims about causality over time,” Kautz and Alloy explained.

“Future studies should utilize additional time points that would allow us to examine more sensitive patterns of biological changes across adolescence, a critical period of development during which many psychological disorders begin to emerge at a clinical level.”

“Questions that still need to be addressed include: Do increases in inflammatory activity lead up to (and perhaps cause) increases in symptoms of depression following a stressful event? Alternatively, does increased inflammation and increased depression occur together in the wake of stressors? Also, what is the impact of early childhood stress, in addition to the influence of recent life stress, on patterns of inflammation across time?” the researchers said.

The study, “Longitudinal changes of inflammatory biomarkers moderate the relationship between recent stressful life events and prospective symptoms of depression in a diverse sample of urban adolescents“, was authored by Marin M. Kautz, Christopher L. Coe, Brae Anne McArthur, Naoise Mac Giollabhui, Lauren M. Ellman, Lyn Y. Abramson, and Lauren B. Alloy.