How Chronic Stress Affects Your Cells: What the Research Shows

Most people accept that long-term stress is bad for health. What is less obvious is how a psychological experience, such as worry about money or caring for a sick relative, could leave a measurable mark inside cells. Over the past three decades, researchers have begun to trace that path, through stress hormones, the immune system and mitochondria. This article sets out what the research shows, and where the evidence is still thin.

The stress response and its costs

When the brain perceives a threat, it activates the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system, releasing cortisol and adrenaline. In the short term this is protective: it mobilises energy and prepares the body to respond.

In a 1998 review in the New England Journal of Medicine, the neuroendocrinologist Bruce McEwen described how the same stress mediators that protect the body in the short term can cause harm when they are activated too often or for too long, or fail to switch off. He called the cumulative wear and tear on the body allostatic load [1]. The idea is central to much of the research that followed.

Telomeres and cellular ageing

Telomeres are protective caps of repeated DNA at the ends of chromosomes. They shorten as cells divide, and very short telomeres are associated with cellular ageing. The enzyme telomerase can help maintain them.

In a 2004 study in the Proceedings of the National Academy of Sciences, Elissa Epel, Elizabeth Blackburn and colleagues studied 58 healthy women, including mothers caring for a chronically ill child. Both how stressed the women felt and how long they had been caregiving were associated with higher oxidative stress, lower telomerase activity and shorter telomeres in their immune cells. The women reporting the highest stress had telomeres shorter on average by the equivalent of at least a decade of additional ageing compared with those reporting the lowest stress [2].

The study was influential but observational and relatively small, so it shows an association rather than proving that stress caused the shorter telomeres. The biology of telomeres and ageing is covered in our guide to the biology of ageing.

Stress and inflammation

Cortisol normally helps keep inflammation in check. One proposed way that chronic stress could promote inflammation is by making immune cells less responsive to cortisol’s signals, a state called glucocorticoid receptor resistance.

A 2012 study in the Proceedings of the National Academy of Sciences tested this idea using controlled exposure to a common cold virus. Healthy volunteers who had recently experienced a long-term threatening stressful event showed greater glucocorticoid receptor resistance, and that resistance predicted a higher risk of developing a cold. In a second group, greater resistance predicted higher production of inflammatory signalling proteins after infection [3]. The findings support a plausible link between chronic stress and poorly regulated inflammation, explained further in our guide to inflammation.

Stress and mitochondria

Mitochondria have been proposed as a meeting point between psychological stress and biology, because they respond to stress hormones and supply the energy the stress response needs. A 2018 systematic review in Psychosomatic Medicine by Martin Picard and Bruce McEwen identified 23 experimental studies of psychological stress and mitochondria. All were in male laboratory animals; 19 found adverse effects of stress on mitochondria, while 4 found increases in mitochondrial function or size [4].

The review found only six human studies, all observational and mostly measuring indirect markers. The authors concluded that stress influences mitochondrial biology, while highlighting the limitations of the current evidence in people [4]. Our guide to mitochondria explains their wider role.

Can the effects be changed?

Researchers have begun to test whether stress-reducing practices affect these cellular markers. In a 2011 study in Psychoneuroendocrinology, 30 people who completed a three-month intensive meditation retreat had higher telomerase activity in their immune cells at the end of the retreat than a matched wait-list group of 30 [5]. Telomerase was measured only once, after the retreat, and the setting was far from everyday life, so the findings are preliminary.

Other factors studied in relation to cellular stress markers include physical activity and sleep, covered in our guides to exercise and your cells and sleep and cellular repair.

What remains unknown

Most human evidence linking stress to cellular damage is observational, which makes it hard to separate the effects of stress from related factors such as sleep, diet, smoking and income. Many measurements are taken from blood immune cells, which may not reflect what happens in other tissues. And people differ widely in how they respond to the same stressor [1, 4].

The research does suggest that the effects of chronic stress reach beyond mood, into hormonal, immune and cellular systems. How large those effects are, and how much they can be reversed, is still being worked out.

References

1. McEwen BS. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine. https://doi.org/10.1056/NEJM199801153380307
2. Epel ES, Blackburn EH, Lin J, et al. (2004). Accelerated telomere shortening in response to life stress. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.0407162101
3. Cohen S, Janicki-Deverts D, Doyle WJ, et al. (2012). Chronic stress, glucocorticoid receptor resistance, inflammation, and disease risk. Proceedings of the National Academy of Sciences. https://doi.org/10.1073/pnas.1118355109
4. Picard M, McEwen BS. (2018). Psychological stress and mitochondria: a systematic review. Psychosomatic Medicine. https://doi.org/10.1097/PSY.0000000000000545
5. Jacobs TL, Epel ES, Lin J, et al. (2011). Intensive meditation training, immune cell telomerase activity, and psychological mediators. Psychoneuroendocrinology. https://doi.org/10.1016/j.psyneuen.2010.09.010

Redox News Today reports on published research for general interest. This article is not medical advice. Last reviewed October 2026.