There are several moments in life when everything feels overwhelming. Stress piles up from work, responsibilities, and personal challenges, and people often try to reorganise their lives in search of balance. During such phases, individuals commonly focus on changing routines, improving habits, or reducing external pressures. But what if one overlooked factor also plays a role in how stressed or healthy we feel - the people around us?
A new study published in the journal Proceedings of the National Academy of Sciences (PNAS) suggests that the individuals who frequently create conflict, criticism or stress in our lives may actually accelerate biological ageing. Researchers describe such individuals as “hasslers”, people who consistently create problems, tension or emotional strain through negative behaviour.
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The findings highlight how social environments can influence physical health, not just mental well-being.
Can toxic people really speed up ageing?
The study suggests that individuals who regularly create stress in someone’s life, referred to by researchers as “hasslers”, may indeed have measurable effects on physical health. According to the findings, these difficult relationships can increase stress levels and accelerate biological ageing by about 1.5 per cent.
To examine this, the researchers analysed data from more than 2,000 people who participated in a large health survey. Participants were asked detailed questions about their social relationships during the previous six months. Specifically, they were asked how often someone in their lives had “hassled them, caused problems or generally made their lives more difficult.”
Along with these responses, participants also provided saliva samples, allowing scientists to study biological markers of ageing by analysing changes in DNA. These molecular signals help estimate what researchers call biological age, an indicator of how well the body’s cells are functioning compared with a person’s actual chronological age.
In simple terms, a higher biological age means that the body’s cells are deteriorating faster than expected for someone’s age. This difference between chronological and biological age can have significant health implications. Faster biological ageing has been linked to a higher risk of chronic conditions, including cancer, dementia and other age-related diseases.
The analysis revealed a clear pattern: individuals who reported more difficult people in their lives tended to show faster biological ageing. “Each additional hassler is associated with faster biological ageing,” the paper noted.
Importantly, the effect appeared to be particularly strong when the stressful individual was a family member. “[There are] especially pronounced effects when the hassler is a family member,” the researchers said, adding that such relationships may be harder to avoid because of emotional or social obligations.
Overall, the findings point to the hidden physiological costs of persistent social stress. As the researchers wrote, “This study highlights that the ‘dark side’ of social connections can wear down physiological resilience and hasten aging and the development of multiple morbidities.”
When the scientists examined the data in more detail, they found that each additional hassler was associated with roughly a 1.5 per cent increase in the pace of biological ageing.
For example, the researchers estimated that a person exposed to one additional hassler might age about 1.015 biological years for every calendar year.
“Although this yearly increase is modest, it accumulates over time,” the researchers wrote in the journal Proceedings of the National Academy of Sciences. “Over a 10–year period, this faster rate results in about 1.8 extra months of biological aging for those with an additional hassler.”
The study also found differences in how people experience these stressful relationships. Women tended to report having more difficult individuals in their lives than men, according to the analysis. Within families, parents and children were more commonly identified as sources of stress than spouses.
Interestingly, spouses who were identified as hasslers did not appear to significantly influence biological age. The researchers suggested that this may be because marital relationships often include a mix of support and strain, meaning the stress created by a spouse may be partly balanced by emotional support.
Outside the family, people were more likely to identify roommates, neighbours and coworkers as hasslers, while friends were less frequently described in this way.
The researchers emphasised that such stressful relationships are often normalised in everyday life. “In everyday life, many individuals routinely encounter people who create problems or make life more difficult—who we refer to as hasslers,” they wrote. “Their familiarity often leads people to normalise and endure them, which has resulted in surprisingly little attention to their long–term health implications.”
Beyond biological ageing, the study also found broader health effects linked to these negative social ties. Individuals who reported more hasslers were more likely to experience poorer general health, worse mental health and poorer physical health overall.
According to the authors, these patterns suggest that negative relationships function as persistent sources of stress. The findings provide evidence that such ties “operate as potent, chronic stressors,” the researchers said.
As a result, these stressful social interactions may represent a hidden risk factor for health. “These results suggest that the hasslers in one's social environment may constitute an overlooked but consequential biological risk factor,” the researchers concluded.
The study also offers insight into the biological mechanisms that may explain this link. Negative social interactions can repeatedly activate the body’s hypothalamic–pituitary–adrenal (HPA) axis, which plays a central role in regulating the body’s stress response.
This system involves several organs that release stress-related hormones. When individuals encounter frequent conflict or tension, the body responds by activating these pathways and releasing hormones such as cortisol and adrenaline.
These hormones help the body deal with immediate threats or challenges. However, when stress becomes chronic, as may happen when someone repeatedly interacts with difficult people, the continued activation of these systems can take a toll on both mental and physical health.
Prolonged exposure to stress hormones can increase feelings of anxiety and depression, the researchers noted. At the same time, chronic social stress can trigger inflammation in the body, which has been linked to a wide range of health conditions.
Over time, this persistent inflammatory response may contribute to faster biological ageing, providing a possible explanation for the patterns observed in the study.
Limitations of the study
The researchers also acknowledged limitations that should be considered when interpreting the findings. One key limitation is that the study was cross-sectional, meaning it examined data from participants at a single point in time. Because of this design, the researchers noted that they cannot confirm a direct cause-and-effect relationship between difficult social ties and biological ageing. “Because our analyses are cross-sectional, we cannot establish a definitive causal pathway between negative ties and biological ageing,” the authors wrote, adding that longitudinal or quasi-experimental studies would be needed to determine whether such relationships truly accelerate ageing over time.
The team also accounted for several alternative explanations by adjusting for factors such as self-perception bias, occupational stress, adverse childhood experiences, existing health conditions and smoking behaviour. While these checks strengthened the results, the authors emphasised that the findings “should not constitute causal estimates.”
Another limitation is that the identification of “hasslers” relied on participants’ self-reports, which may reflect personal perceptions or personality traits rather than entirely objective social dynamics. As the researchers noted, these responses could be influenced by “stable personality traits, or broader appraisal tendencies that shape how social interactions are perceived and recalled.”
The study may also be affected by mortality selection, meaning individuals experiencing the highest stress or poorest health may not have been included in the sample. In addition, the survey captured only one indicator of negative interactions, making it difficult to distinguish between different types of relational strain. Future research, the authors suggested, should include richer measurements to better understand how various forms of negative social ties influence health and ageing.
This story is done in collaboration with First Check, which is the health journalism vertical of DataLEADS
