You probably already know who they are.
The person who calls and leaves you more drained than before they called. The family member whose name on your screen makes your stomach tighten. The colleague who can turn any room heavy just by walking into it. You’ve always known, somewhere in your gut, that these people cost you something. You just didn’t know how literally true that was.
Science just put a number on it.
Nine Months. Per Person.
A study published in the Proceedings of the National Academy of Sciences, one of the most respected scientific journals in the world, has found that the difficult, draining people in your life are accelerating your biological aging. Not just making you feel older. Actually making your body age faster, at the cellular level.
The researchers studied 2,345 adults and found that for every “hassler” their word for someone whose presence in your life creates consistent stress and friction your biological age increases by roughly nine months, and your rate of aging speeds up by about one and a half percent.
To understand why that matters, you need to understand the difference between your calendar age and your biological age. Your birthday tells you how many years you’ve been alive. Your biological age tells you how fast your body is actually deteriorating how your cells are functioning, how your DNA is expressing itself, how quickly your internal systems are wearing down. Two people who are both 45 years old can have very different biological ages depending on the lives they’ve lived.
The researchers measured this using something called DNA methylation essentially, chemical markers on the DNA that scientists can read like a clock. They took saliva samples from participants and used those markers to estimate how old each person’s body actually was, regardless of their birth year.
What they found was stark. People who had difficult, negative relationships in their lives looked measurably older at the cellular level than people who didn’t even when every other factor was accounted for.
The Hassler in Your Life Is Probably Someone You Love
Here’s the part that stings.
It’s not the stranger who cuts you off in traffic. It’s not the rude person in the checkout line you’ll never see again. Fleeting irritations don’t do this kind of damage. What ages you is the chronic, unavoidable, ongoing stress of a difficult relationship with someone you can’t simply walk away from.
Which is why the study found that when the “hassler” is a family member, the damage is worse.
Think about it. You can avoid a draining acquaintance. You can quietly stop replying to someone’s messages. But family? The family shows up at the dinner table. Family is there at every wedding, every holiday, every milestone. The door is always open, even when you wish it wasn’t. And that continuous, inescapable exposure to someone who unsettles you that’s the kind of stress that quietly works away at your biology over months and years.
Around 30 percent of the people in the study had at least one hassler in their lives. That’s roughly one in three people carrying around a relationship that is, without them necessarily realizing it, making them age faster.
What “Chronic Stress” Actually Does to Your Body
The study identifies these negative relationships as “chronic stressors,” and that phrase is worth sitting with.
We tend to think of stress as a temporary thing. A bad day. A difficult conversation. A looming deadline. You feel it, you survive it, you move on. But chronic stress, the kind that comes from being regularly around someone who unsettles you, dismisses you, criticizes you, or simply drains you doesn’t work like that. It keeps the body in a low-level state of alert that it was never designed to sustain for long periods.
When your nervous system is persistently activated, it affects inflammation levels, hormonal balance, immune function, and the very mechanisms your cells use to repair and replicate themselves. Over time, this shows up in the data. It shows up in the DNA. It shows up as someone who looks and functions biologically older than they should.
This is not a metaphor. This is measurable biology.
So Should You Just Cut Everyone Off?
The researchers are careful here, and it’s worth being careful too.
Loneliness is its own health crisis. Human connection is not optional, it’s a genuine physiological need, as essential to long-term health as sleep or food. The answer is not to become a hermit, burn your phone and move somewhere remote where no one can reach you.
The answer, the researchers suggest, is something more nuanced and, honestly, more difficult: learning to set limits on relationships that cost you more than they give.
Not every relationship deserves equal time and energy. Some people in your life fill you up. Others empty you. Most of us already sense which is which we just haven’t always given ourselves permission to act on that knowledge, especially when family or long history is involved.
The simple, practical implication of this research is that protecting your time and energy is not selfish. It is, quite literally, a health decision.
The Quiet Wisdom Nobody Talks About
There’s a version of this idea in almost every culture in the world. Every language has a saying about it. In English, we’ve always said “you are who you surround yourself with” though we usually mean it in terms of character and ambition, not biological cellular aging.
But the science is pointing at something older and simpler than that. The people you spend your days with are shaping your body. Not just your mood. Not just your habits. Your actual, physical, measurable health.
People will spend enormous amounts of money on supplements, skincare, fitness plans and sleep optimization in the hope of slowing down aging. And all of that may help. But buried in a scientific journal this week is a reminder that one of the most powerful things you can do for your long-term health is also one of the most overlooked:
Look honestly at the relationships in your life. Notice which ones leave you lighter, and which ones leave you heavier. And stop treating that difference as something you simply have to accept.
Your body has been keeping score all along. Now you have the research to prove it.
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