Approximately 20% of American adolescents experience a mental health disorder each year, a number that has been on the rise. Genetics and life events contribute, but because so many factors are involved, and because their influence can be subtle, it’s been difficult for researchers to generate effective models for predicting who is most at risk for mental health problems.

A new study from researchers at Washington University School of Medicine in St. Louis provides some answers. Published Sept. 15 in Nature Mental Health, it mined an enormous set of data collected from pre-teens and teens across the U.S. and found that social conflicts—particularly family fighting and reputational damage or bullying from peers—were the strongest predictors of near-and long-term mental health issues.

The research also revealed sex differences in how boys and girls experience stress from peer conflict, suggesting that nuance is needed when assessing social stressors in teens.