Chronic stress with elevated cortisol levels has the strongest evidence for a negative effect on the skin: more wrinkles, a weaker skin barrier and more DNA damage in skin cells. The association with accelerated biological ageing (measured via epigenetic clocks) was demonstrated in a large observational study, but another study found no such association. The evidence is therefore promising but not yet conclusive, and rests primarily on observational studies. The most concrete practical tool for actively lowering cortisol is massage therapy, which reduced cortisol levels in multiple studies.
Cortisol is the hormone your body produces in response to stress. In the short term that is useful, but when levels remain elevated for a long time there is clear evidence that it accelerates ageing processes, both in the skin and possibly deeper in the body. The strength of that evidence varies by organ and by type of study.
The most direct evidence concerns the skin. A clinical study (with the caveat that it was funded by cosmetics company Coty) found that moderately stressed individuals had approximately 33% more fine lines and textural changes than mildly stressed individuals, along with a weaker skin barrier and more DNA damage in skin cells. Additional laboratory research shows that the skin also produces cortisol locally through the enzyme 11-beta-HSD1. Too much of this local cortisol inhibits wound healing and promotes skin ageing. At menopause, when oestrogen declines, the hormonal balance shifts in a way that amplifies cortisol's influence on the skin and contributes to dryness, thinning and wrinkles, although the precise role of cortisol in this is difficult to disentangle from the drop in oestrogen.
At the level of the biological clock, results are mixed. In a large American study with 969 participants, higher cortisol levels were associated with a higher biological age according to multiple epigenetic measurement methods. In particular, the ratio between cortisol and the protective adrenal hormone DHEAS was the strongest predictor. This is, however, an association: it does not automatically mean that cortisol directly accelerates your biological clock. A different study involving 296 working individuals found no link at all between work-related stress, elevated cortisol (measured in hair) and accelerated epigenetic ageing. Work stress did predict burnout and depression, but not through the biological clock. This nuances the popular idea that stress automatically drives up your biological age.
A separate point of attention is the brain. A review article describes how chronic exposure to UV light activates a stress hormone pathway in the skin that raises cortisol levels in the blood. That elevated cortisol appears to inhibit the formation of new brain cells in the hippocampus, a brain region important for memory and learning. This is, however, based on a review without its own measurements, and the contribution of this specific mechanism to brain ageing in humans has not yet been demonstrated.
What can you practically do with this? Massage therapy has been linked in multiple studies to lower cortisol levels, presumably because pressure stimulation activates a calming nervous system response. The methodology of those studies is of varying quality, but it is one of the better-supported non-pharmacological approaches to lowering cortisol. The evidence for the skin effects of stress is real enough to take chronic stress seriously as an ageing factor, but it is too early to say on this basis that cortisol is the sole or dominant cause of ageing.
Seven sources: five human studies (two using epigenetic clocks, one clinical skin exploration, one study in working individuals, one in 969 persons), one review article (UV/brain), one laboratory study (local cortisol in skin). One study funded by Coty (cosmetics), noted alongside the relevant finding. No randomised intervention trial with ageing as the primary outcome.