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Substance use by peers and family may affect adolescent substance use, yet the relative influence may shift during adolescence as youth differentiate themselves from family and more closely affiliate with peers. This study examined trends in concordance of adolescent cigarette, alcohol and marijuana use and corresponding perceived use by friends and family members during middle and high school.

Data are from a longitudinal cohort of 12,038 youth who completed up to five surveys during grades 6–12. At each wave, adolescents reported past month use of cigarettes, alcohol and marijuana, as well as perceived use by their best friend, older sibling and most important adult figure. For each substance, we used time-varying effect models to estimate how associations between adolescent use and perceived use varied across grade.

For all substances, concordance with best friend use was …