A parent who can't get through a phone call without a cutting remark. A sibling whose entire personality seems engineered to cause problems. New research suggests these relatives may be causing them to age faster, too.
Researchers found that family members, more than coworkers, neighbors, or even difficult spouses, showed the strongest links to accelerated biological aging when they regularly hassled, burdened, or created problems for someone in their network. Having any family member in that category was associated with a biological age roughly a year older than peers of the same calendar age, and with cells aging measurably faster. Spouses showed no statistically meaningful effect on the aging clocks used in this study. According to the study, the family ties hardest to exit and loaded with the most obligation — parents, children, siblings — may be doing the most quiet biological damage.
Scientists drew on a large health study conducted across Indiana called the Person-to-Person Health Interview Study. To measure biological aging, the team analyzed DNA extracted from participants' saliva samples, using two well-validated molecular tools called GrimAge2 and DunedinPACE. These tools read chemical changes in DNA that track how fast the body's cells are deteriorating. GrimAge2 captures cumulative biological age relative to calendar age. DunedinPACE works more like a speedometer, capturing the current rate of cellular aging.
To identify who qualified as a "hassler," participants named the people in their lives and rated whether each person "often" hassled them, caused problems, or made their lives more difficult. Occasional friction didn't count. Hasslers were people who did this regularly. About 29% of the participants reported having at least one hassler in their close network. Roughly 10% had two or more.
The biological costs tracked closely with relationship type. Family hasslers, specifically parents, children, and siblings, showed the most consistent links to both measures of accelerated aging. Spouse hasslers showed no statistically significant association with either measure.
The paper offers a structural explanation for why family stands out. Kin ties carry obligation; they are harder to renegotiate or exit than friendships or even work relationships. When a family member is also a source of repeated stress, there are fewer options to disengage and fewer compensatory mechanisms to offset the harm. The structural embeddedness that usually signals social protection can become a pathway for chronic stress when anchored in a difficult relationship, turning what would normally be a source of support into a source of biological risk.
Across the entire sample, each additional hassler in a person's close network was associated with roughly nine months of extra biological age and a pace of cellular aging about 1.5% faster per year. To benchmark those numbers, the authors compared them to smoking. The hassler association corresponded to roughly 13 to 17% of the biological aging gap typically observed between non-smokers and smokers.
Biological aging was far from the only health domain affected. Each additional hassler was associated with higher depression and anxiety scores, poorer self-rated mental and physical health, higher BMI, and higher rates of multiple chronic conditions occurring at the same time. Chronic social stress appears to put the body's internal alarm systems on a slow burn. Over time, that persistent activation feeds inflammation at the molecular level, wearing down the body across multiple systems at once.
Most people endure difficult relatives because it feels like the only option. What this research adds is that the body doesn't simply absorb that strain and move on. It registers it, and over time, the registration shows up at the cellular level.