Picture whoever comes to mind when you think of the person in your life who makes things harder.
Maybe it’s a parent who reliably says the wrong thing. A colleague you schedule around. A sibling you brace for before family events.
There’s probably someone — and there’s probably a particular feeling in your body that comes with thinking about them. A slight tightening. A low hum of dread. You’ve likely told yourself it’s not a big deal.
New research published in PNAS suggests it might be worth taking that feeling more seriously.
What the study found
Researchers at New York University and Indiana University analyzed data from 2,345 adults living in Indiana, ranging in age from 18 to 103. Participants described their social networks in detail, identifying people they regularly interacted with — and specifically anyone who regularly caused them problems or made their lives harder. The researchers called these people hasslers. They then analyzed saliva samples from participants using epigenetic clocks, a laboratory tool that reads chemical changes on DNA to estimate how fast a person’s cells are actually aging, independent of their chronological age.
Nearly 30 percent of participants reported having at least one hassler in their close social circle. And the presence of hasslers was associated with measurable changes in biological aging. Byungkyu Lee, PhD, lead author and assistant professor of sociology at NYU, described the scale of the effect: “It is about 9 extra months on the odometer and a 1.5% faster speedometer reading. Although the effect of each hassler might seem small, biological aging is cumulative, so even modest differences in pace can add up over years. To put this in perspective, the hassler association corresponds to roughly 13% to 17% of the estimated effect of smoking on these same aging measures. That is not trivial.”
The study also found links between hassler exposure and higher systemic inflammation, elevated rates of depression and anxiety, and a higher body mass index. These aren’t separate findings that happen to correlate — they point toward a consistent picture of what chronic interpersonal stress does to the body over time.
Why family members hit harder than spouses
One of the more specific findings in the study is that not all hasslers are equal. Family members — parents, children, siblings — were associated with stronger effects on biological aging than spouses who caused difficulties. Lee’s explanation for this is about the nature of those ties: “That suggests the ‘stickiness’ or inescapability of certain roles may be especially important.” You can manage down a friendship. You can change jobs. You can, in time, create distance from an acquaintance who drains you. The person at Sunday dinner is a different calculation entirely.
Spouses who functioned as hasslers showed a weaker association, possibly because marriage tends to mix negative exchanges with positive ones in ways that other family relationships sometimes don’t. The research doesn’t suggest spouses can’t be a source of chronic stress — it suggests the family role, with its embedded obligations and shared histories, may make the stress harder to metabolize.
Who tends to have more hasslers
Hassler exposure wasn’t evenly distributed across the sample. Women were more likely to report having difficult people in their close networks than men. So were daily smokers, people in poorer baseline health, and those who had experienced adverse childhood events. This clustering matters because it suggests that people who already face greater biological or social vulnerability may also be disproportionately exposed to the relational stress that compounds it. The research notes the associations but can’t fully untangle why this pattern holds.
What to do with this information
The study is observational, which means it can identify an association between hassler exposure and biological aging but can’t prove that difficult people directly cause that acceleration. Lee is explicit about this: “The associations are consistent with hasslers functioning as chronic stressors that drive biological wear and tear, but alternative explanations exist” — including the possibility that people aging faster may become more irritable, which in turn affects how they perceive interactions. The researchers took steps to control for this, but causality remains unconfirmed.
The practical implication the research does support is about recalibrating how much energy you put into difficult relationships rather than eliminating them. Co-author Brea Perry, PhD of Indiana University put it this way: “As soon as you recognize that someone who is a hassler has these negative biological consequences for you, set limits on the effort you’re putting into that relationship.” That’s a meaningfully different instruction from “cut them off.” Limits on effort — lower investment, lower availability, less of yourself in the space where the friction lives.
It’s also worth holding the other side of this. Social isolation carries its own serious health risks, documented across decades of research. The goal isn’t fewer relationships. It’s more clarity about which ones cost more than they give, and a more deliberate approach to where you put your energy. Lee describes it this way: “One broader message is that ‘social health’ isn’t only about having people around. It is also about whether those close ties are a source of support or a source of chronic strain.”
I think about this in terms of something I’ve always believed about efficiency: the effort you invest should be proportional to the return you get. That’s true at work, it’s true in how you structure a day, and apparently it’s true at the level of your cells. The relationships that repeatedly cost you something — that have you bracing, adjusting, managing — aren’t neutral. They’re a tax. What you do about that depends on the relationship, the circumstances, and what’s actually possible. But knowing it has a measurable biological dimension changes how seriously you take the question.
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