Pubertal timing and substance use: Associations between and within families across late adolescence

In the present study, between-family analyses of data from adolescent twin girls offer new evidence that early menarche is associated with earlier ini tiation and greater frequency of smoking and drinking. The role of personal ity factors and peer relationships in that association was investigated, an d little support was found for their involvement. Novel within-family analy ses replicating associations of substance use with pubertal timing in contr asts of twin sisters selected for extreme discordance for age at menarche a re reported. Within-family replications demonstrated that the association o f pubertal timing with substance use cannot be explained solely by between- family confounds. Within-family analyses demonstrated contextual modulation of the influence of pubertal timing: Its impact on drinking frequency is a pparent only among girls in urban settings. Sibling comparisons illustrate a promising analytic tool for studying diverse developmental outcomes.