Teens who often display aggressive behavior may experience physical health effects that persist into adulthood, according to new research published by the American Psychological Association. The study found a link between early adolescent aggression and accelerated biological aging, as well as higher body mass index (BMI) by age 30.
The research, which appeared in the journal Health Psychology, followed 121 middle school students from both suburban and urban areas in the Southeastern United States. The group included 46 males and 75 females. Researchers collected information on aggression through self-reports, parent reports of family conflict, and peer reports about relationship behaviors from age 13 onward. When participants turned 30, their biological aging was measured using blood-based biomarkers.
"There were 12 markers in all, which included C-reactive protein, blood sugar, white blood cell count, etc. We then used a recently developed algorithm that combines all of these and yields an estimate of a person's biological age, which turns out to be a better predictor of their health and eventual mortality than their actual chronological age," said Allen.
To estimate biological aging, the researchers used two validated methods: the Klemera-Doubal approach and PhenoAge. These methods combine several indicators such as blood pressure, inflammation levels, glucose concentration, cholesterol values and immune system function to determine how old a person’s body appears compared with their actual age.
"Both methods showed that higher levels of aggression in early adolescence predicted more advanced biological age by 30, even after accounting for gender, family income, serious childhood illness and adolescent body shape," said Allen.
The findings also indicated that males and individuals from lower-income families tended to show faster rates of biological aging. Further analysis linked these patterns to ongoing relationship challenges: boys reported more conflict with fathers while teens from lower-income backgrounds were more likely to act punitively toward peers.
According to Allen's explanation, early aggression alone did not lead directly to faster aging unless it resulted in continued relationship difficulties over time. Teens with higher initial aggression were more prone to argue with parents or mistreat friends as they matured; these sustained struggles—not just early aggressive acts—were associated with accelerated aging later on.
"This study does not prove that teenage aggression directly causes faster aging," Allen said. "Other factors we didn't measure may also be playing a role, and it's likely that what really matters is how those early behaviors turn into later relationship problems. We also can't yet say whether it's aggressive actions, hostile attitudes or a mix of both that makes the difference."
Allen emphasized that early signs of relationship problems could serve as indicators for future health risks. The results highlight the potential value of supporting adolescents in developing healthier relationships—a step that could benefit mental and physical health throughout life.
"Adolescents are often mocked for treating their relationships as matters of life and death," Allen said. "These findings suggest that, in some ways, they are really on to something, which is that relationships beginning in adolescence, and especially patterns of conflict and aggression that begin in adolescence, do seem to have long-term fundamental physical health implications."
