Being poor is about more than just finances. A growing body of research has shown for awhile that the cycle of poverty is also psychological—and physiological. Having no money makes people stressed, which changes their outlook on life and how they make decisions. They become averse to risk and more focused on the short term. For children born into poverty, the effects of poverty can start before birth and put them at higher risk for mental disorders and depression.
A new study, published in Molecular Psychiatry, delves deeper into the biological underpinnings of this sad cycle, and it shows that poverty doesn’t just influence prenatal development, but can have an effect on a low-income person straight through adolescence.
Epigenetics is a relatively new field of study that has found that, even though a person’s DNA is fixed throughout their life, a person’s environment and experiences can alter the chemical environment surrounding their DNA and change how their genes are expressed, causing them to become more active or inactive. A number of recent studies have shown that stress and adversity are two of the most important types of experiences that affect DNA in this way, increasing the risk of various psychological disorders.
The study, by scientists at Duke University, was a detailed investigation into how their socioeconomic situations change the expression of a gene linked to depression.
Before the study, the researchers, from Duke University, knew that the gene, SLC6A4, helps control the brain’s level of the mood-regulating hormone serotonin. Chemical tags present near this gene can change its activity and also affect the activity of a region of the brain called the amygdala, which is responsible for responding to threatening situations and has been previously been linked to depression.
Over two years, the researchers looked at the brains and blood samples of a group of 132 Caucasian adolescents between the ages of 11 to 15, about half of whom were at risk for depression because of a family history. They found that the poorest subjects had acquired more chemical tags near this gene—potentially changing the levels of serotonin in their brains. They also looked at all of the subjects in an MRI and found that the poorest children had more active amygdalas.
The results came to fruition a year later, when they came back to the kids. Those with higher amygdala activity, especially those with a family history of depression, were more likely to report depression symptoms.
The study is early work with a small sample group. But it does indicate some of the complex ways that poverty might have effects on children that we don’t yet understand, and help explain why they may struggle as adults.
University of California, Davis’s Ross Thompson, who directs the Social and Emotional Development Lab and wasn’t involved in research, says the study is fascinating because it extends our understanding of how experience can alter gene expression and resulting behavior—but he cautions against interpreting its findings too broadly. For example, it’s hard to say what aspect of low socioeconomic conditions contributes to changes in gene expression—it could be stress, but it might be something else entirely, like air pollution.
The long-term goal of the research, says study author Joanna Swartz, is to identify biological signs that help doctors understand who is at risk for depression, helping to personalize treatment. This work ties to an emerging field, called "precision public health," that tries to prevent disease and reduce health disparities by better predicting who is at risk for illness.
"I think one aspect of this research that’s exciting is that it suggests that our biology is not necessarily fixed from an early age," Swartz said in a Q&A with ResearchGate. "This opens the possibility that perhaps our biology can change for the better, given positive environmental contexts."
As for using these results to help people in poverty? That’s probably too soon. But Thompson notes that recent animal research has shown that not only negative, stressful experiences but also positive, socially supportive experiences can contribute to epigenetic changes in gene expression.
"If this proves true for humans, it would suggest that enhancing social support to children and youth would be valuable for its effects on gene expression as well as for its other benefits," he says.
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