Friends Forever? Correlates of High School Friendship (In)stability from Adolescence to Young Adulthood.

Although friendship instability is common throughout adolescence and young adulthood, experiencing high rates of relational turnover is associated with negative health outcomes and lower educational attainment. Currently, we know little about whether the rates and correlates of friendship instability change during the transition to young adulthood, even though this period is characterized by significant life events such as high school completion. Using new and unique network data from the PROSPER study, we address this gap by following the trajectories of roughly 2,000 respondents' close friendships from the start of high school to one year after graduation. Results suggest that friendship dissolution is frequent after high school, with only 35% of friendships reported in respondents' senior years of high school remaining intact one year later. Similar histories of substance use were more impactful in inspiring friendship persistence after high school than during adolescence, while the role of shared sociodemographic characteristics did not vary across developmental periods. After high school, young people were also more likely to maintain friendships with peers who previously reciprocated these relationships and reported friends in common. Our findings underscore how friendship dynamics change at the start of young adulthood in ways that carry implications for behavioral trajectories and life outcomes.