Stress: It’s a common, and sometimes unavoidable, affliction in the modern world. Adults and even sometimes children are faced with various pressures at school, work and home, whether it has to do with career, finances, loss or bereavement, bullying or social isolation.

Prolonged stress has been linked to many health problems, including premature aging and increased risk of stroke and other chronic illnesses. However, the way stress actually negatively affects our biological processes and physical well-being is still being investigated. A recent study out of the Ohio State University found that chronic stress can impact gene activity in immune cells, causing them to fire up to fight a nonexistent infection or trauma, leading to an overabundance of inflammation. “[W]hat this suggests is that if you’re working for a really bad boss over a long period of time, that experience may play out at the level of gene expression in your immune system,” John Sheridan, professor of oral biology and associate director of Ohio State University’s Institute for Behavioral Medicine Research, said in a press release.

Inflammatory Cells Fighting A Nonexistent Infection

The scientists tested their hypothesis on mice – a model they’ve been using for a decade to study chronic stress effects, specifically stress associated with social defeat. The mice in the test were allowed to create a hierarchy, after which an aggressive male was repeatedly placed into the cage. The placement of the intrudcer caused a “fight or flight” response in the rest of the mice as they were defeated. “These mice are chronically in that state, so our research question is, ‘What happens when you stimulate the sympathetic nervous system over and over and over, or continuously?’ We see deleterious consequences to that,” Sheridan said in the press release.

When stress permeates the body, white blood cells produced in the bone marrow end up being more inflammatory than if the person wasn’t experiencing stress. When the cells are inflammatory, they are primed and ready to fight against some form of infection or external threat which doesn’t exist. This unnecessary, excessive inflammation, exhibited in the body long-term, is what can trigger cardiovascular disease, diabetes and other disorders.

The researchers analyzed the cells taken from stressed mice, and found that those mice had four times as many immune cells in their blood than non-stressed mice. They also found that some 3,000 genes were expressed at different levels in the cells of stressed mice, typically genes that were pro-inflammatory, or giving the cells an ability to quickly mobilize into fighting mode. “There is a stress-induced alteration in the bone marrow in both our mouse model and in chronically stressed humans that selects for a cell that’s going to be pro-inflammatory,” Sheridan said.

Not Just Stress – Happiness Affects Genes, Too

The concept of stress impacting genes is called conserved transcriptional response to adversity (CTRA), which is a shift in the increased number of pro-inflammatory genes and a decrease in genes involved in antiviral responses. A previous study completed by researchers at UCLA in July of this year came to a similar conclusion, but this time, it was that your happiness can affect your genes, too. What the UCLA researchers wanted to study was how two different types of happiness affected genes. They studied the effect of eudaimonic well-being, which is a type of happiness stemming from a deep sense of meaning and purpose in life, as well as the effect of hedonic well-being, which usually is caused by self-gratification. They found that eudaimonic happiness showed “favorable” gene-expression profiles while hedonic showed “adverse” gene-expression profiles. “What this study tells us is that doing good and feeling good have very different effects on the human genome, even though they generate similar levels of positive emotion,” Steven Cole, a professor of medicine at UCLA who authored the study as well as assisted the Ohio State researchers with their study, said in a press release.

Nicole Powell, a research scientist in oral biology at Ohio State University, said in a statement that the OSU study "provides a nice mechanism for how psychology impacts biology. Other studies have indicated that these cells are more inflammatory [during stress]; our work shows that these cells are primed at the level of the gene, and it’s directly due to the sympathetic nervous system.”

Source: N. D. Powell, E. K. Sloan, M. T. Bailey, J. M. G. Arevalo, G. E. Miller, E. Chen, M. S. Kobor, B. F. Reader, J. F. Sheridan, S. W. Cole. Social stress up-regulates inflammatory gene expression in the leukocyte transcriptome via adrenergic induction of myelopoiesis. Proceedings of the National Academy of Sciences, 2013