A new study has linked exposure to stressful social relationships to accelerated ageing, with researchers warning that frequent interaction with difficult individuals could have measurable effects on human health and longevity.

Professor Luke O’Neill of the School of Immunology at Trinity College Dublin said persistent stress caused by so-called “hasslers” — individuals who regularly irritate, criticise or exclude others — may contribute to biological ageing by damaging DNA.

Speaking on the Pat Kenny Show, Professor O’Neill described stress as a “silent killer” in modern life, citing findings from a United States study involving about 2,500 participants.

According to him, the study found that individuals who frequently experience stress from others show signs of accelerated biological ageing, with observable changes at the cellular level.

“A hassler is someone who’s often hassling you, irritating you or maybe criticizing or excluding you”, he said.

The research suggests that stress triggers chemical changes in the body that leave marks on DNA, a process linked to inflammation and age-related health decline. These biological markers can make individuals appear older than their actual age.

“As we age our DNA gets stained so if a 60 year-old-man has the number of marks that would be associated with being a 70-year-old it means your biological age is 70,” he explained.

He added that factors such as smoking and lack of exercise can intensify these effects, further accelerating the ageing process.

Central to the process is cortisol, a hormone released in response to stress, which researchers believe contributes to faster ageing when present at elevated levels over long periods.

“That’s partly due to cortisol which seems to increase the rate at which you age,” he noted.

The study also examined the sources of stress within close relationships, identifying spouses, siblings and even grandparents among those most commonly perceived as “hasslers”. It found that about 10 per cent of spouses and five per cent of grandparents fall into this category.

Despite the findings, Professor O’Neill said the effects of stress-related ageing are not irreversible and can be mitigated through lifestyle changes, including physical activity and reducing exposure to stressful interactions.

“If you get rid of the hasslers from your life, your ageing process slows down a bit”, he proposed.

He acknowledged, however, that avoiding such individuals may be difficult, particularly when they are family members.

“If they've caused trouble before, don’t meet that person if you can avoid it. It’s harder to do when they’re your family but the more stressed you are the quicker you age,” he added.

Exercise, he said, could help counteract some of the effects by triggering beneficial chemical responses in the body.

“It’s suggested to reverse those effects after someone has bothered you, you can go out, have a jog, run or even go to the gym”, Prof. O’Neill advised.

“It releases things in your body but it doesn’t necessarily remove the stain entirely.”

The findings add to growing evidence linking chronic stress to a range of health conditions, with the researcher warning that unresolved emotional strain can have lasting physiological consequences.

“People have illnesses caused by trauma,” he said.