People who make your life difficult may be doing more than ruining your day — they could be making you age faster at the molecular level.
A new study from researchers at New York University, Utah State University, the University of South Florida, the University of Michigan, and Indiana University has found that having even one persistently difficult person in your social circle is associated with measurably accelerated biological aging, increased inflammation, and a higher burden of chronic disease.
Nearly a third of people have a “hassler” in their network
The researchers analysed data from 2,345 participants in an Indiana probability sample, combining detailed social network surveys with DNA methylation-based epigenetic clocks — biological markers that measure how fast someone is aging at the molecular level, independent of their calendar age.
They defined “hasslers” as people whom respondents said “often” caused them problems or made life difficult. About 29 per cent of participants reported at least one hassler in their close social network, and roughly 10 per cent had two or more.
Hassler exposure was not random. Women were more likely to report hasslers than men. People with more adverse childhood experiences, daily smokers, and those with poorer self-reported health were also more likely to have difficult people in their networks. Notably, having a larger social network increased the chances of having a hassler, though the proportion of hasslers stayed relatively stable regardless of network size.
Each hassler adds about nine months of biological age
Using two advanced epigenetic clocks — GrimAge2, which measures cumulative biological aging relative to chronological age, and DunedinPACE, which captures the current rate of aging — the researchers found consistent associations between hasslers and faster aging.
Each additional hassler was linked to a 1.5 per cent faster pace of biological aging and roughly nine months of additional biological age compared to peers of the same chronological age. Over a decade, the faster aging rate would translate to about 1.8 extra months of biological wear and tear per hassler.
People who reported having any hassler at all showed a 2.6 per cent faster pace of aging and 15 months of accelerated biological age. The effect roughly corresponded to 13 to 17 per cent of the difference in aging seen between smokers and non-smokers.
Not all hasslers are equal
The health impact depended heavily on the type of relationship. Hasslers who were family members — parents, children, siblings — showed the strongest and most consistent links to accelerated aging, likely because these relationships are structurally inescapable and involve enduring obligations.
Non-kin hasslers such as coworkers, roommates, and neighbours also showed significant associations with one of the aging measures, suggesting that even peripheral social strain imposes a cumulative physiological cost.
Spousal hasslers, surprisingly, showed no significant effect on either aging measure. The researchers suggest this may be because marital relationships typically combine both positive and negative exchanges, with the supportive elements partially offsetting the strain.
Across all relationship types, hasslers were characterised by weaker emotional ties to the respondent, more peripheral positions in the social network, and fewer overlapping roles — meaning these are relationships defined more by friction than by richness.
The damage extends well beyond aging
The associations were not limited to epigenetic clocks. Each additional hassler was linked to worse outcomes across a broad range of health measures: a 0.28 standard-deviation increase in depression severity, a 0.25 SD increase in anxiety, higher BMI, a worse waist-to-hip ratio, and greater multimorbidity. The only measure that showed no association was height — a stable biological trait — which the researchers used as a built-in sanity check.
Ruling out alternative explanations
The researchers ran extensive sensitivity analyses to test whether the results could be explained by reverse causation (sicker people attracting more conflict), negative personality traits colouring perceptions, pandemic-era cohabitation stress, or unmeasured confounders.
The associations held up after controlling for pre-existing health conditions, adverse childhood experiences, smoking, occupation, affective disposition, and COVID-19 timing. Longitudinal follow-up data showed that baseline hassler exposure predicted worsening health even after adjusting for initial health status, supporting the interpretation that the social strain precedes the health decline rather than the other way around.
A formal sensitivity analysis estimated that nearly half the sample would need to be replaced with counterfactual cases to nullify the findings, and any unmeasured confounder would need to be stronger than virtually all observed covariates to explain the results away.
The study was published in the Proceedings of the National Academy of Sciences on February 18, 2026.
Source: Lee, B., Ciciurkaite, G., Peng, S., Mitchell, C. & Perry, B. L. (2026). Negative social ties as emerging risk factors for accelerated aging, inflammation, and multimorbidity. Proceedings of the National Academy of Sciences, 123(8), e2515331123.
