A new study published in Brain, Behavior, and Immunity sheds light on the complicated relationship between childhood poverty and inflammation. Poverty was “consistently and reliably” associated with inflammation in childhood, but the picture became more muddled when examining the influence of childhood socioeconomic status on inflammation in adulthood.

“As a (soon to be) clinical psychologist interested in integrated care in medical settings, I am skeptical about the dichotomy healthcare has historically created between mental and medical disorders and the disjointed way in which treatment is provided,” said study author Izabela Milaniak, a clinical psychology PhD candidate at the University of Pennsylvania.

“This is how I became interested in the research linking chronic inflammation as a common determinant of both medical diseases such as diabetes and chronic heart disease and what are traditionally thought of a psychological illness such as depression and anxiety disorders.”

“Prolonged activation of the immune system due to ‘fight or flight’ reactions to chronic exposure to stressful environments in childhood such as maltreatment and poverty is linked to over-activation of the immune system leading to wear and tear on the brain and the body resulting in a combination of both mental and medical illness later in adulthood,” Milaniak said.

The researchers conducted a meta-analysis of 35 previous studies on childhood socioeconomic status and inflammatory markers. A meta-analysis is statistical method of combining the results of multiple scientific studies, which helps researchers to better establish the strength of an effect.

Milaniak and her colleagues found evidence that lower childhood socioeconomic status was associated with higher levels of chronic inflammation.

However, the link between socioeconomic status and inflammation became non-significant when analyzing only longitudinal studies that controlled for adulthood socioeconomic status. The results suggest there is an indirect pathway between childhood socioeconomic status and adult inflammatory outcomes. That pathway could be risky behaviors such as smoking.

“The effects of childhood poverty are as complicated to study as they are important. This meta-analysis shows the disparate ways in which researchers can begin to make connections between childhood events and adult health outcomes. Given that SES is not a time-limited exposure, assessing its effects across the lifespan on health outcomes is particularly challenging,” Milaniak explained to PsyPost.

“For example, our meta-analysis found that across the literature, the relationship between childhood socioeconomic status and adult inflammation levels becomes non-significant when taking account of other factors including BMI and smoking along with adulthood SES. This suggests that BMI and smoking can be more accurately conceptualized as part of the pathway between childhood poverty and inflammation rather than confounders.”

The findings also highlight the need for more rigorous longitudinal designs.

“As with most observational research, relationships between variables can never be established as causal. It would be impossible and unethical to randomly assign children to stressful life experiences to definitively say that poverty leads to chronic inflammation. However, there can be clever research designs that can get closer to establishing causality,” Milaniak said.

“Researchers can follow children forward in time, measuring inflammatory markers at multiple points across the lifespan, especially when individuals experience upward economic mobility from childhood to adulthood. I think the continuity or discontinuity in health trajectories will be interesting to see from childhood, into adolescence, and adulthood.”

“Researchers could collect also inflammatory markers from children and adults enrolled in randomized control trials that are designed to reduce family poverty in quasi-experimental designs. Programs like universal basic income are being rolled out in high poverty areas such as Stockton, CA,” Milaniak explained.

“A large body of research has time and again shown the deleterious effect of poverty on children’s emotional, cognitive, neural, and now biological health functioning. Poverty disrupts normative development in such profound ways that we cannot expect children to pull themselves up by their bootstraps without some help.”

“Even resilience comes at a cost as studies show that even children who become affluent in adulthood do not escape the negative health effects of childhood poverty (see citation below). 43% of children in the United States live in low-income families. As those children grow up, the healthcare burden for physical and mental health driven by effects of poverty are profound,” Milaniak added.

The study, “Childhood Socioeconomic Status and Inflammation: A Systematic Review and Meta-Analysis“, was authored by Izabela Milaniak and Sara R. Jaffee.