Sibling popularity: A moderator of sibling influence for adolescent substance use.

Sibling substance use is a known correlate of adolescent substance use. Yet, not all siblings are equally influential. Sibling influence has been found to vary by age gap, sex, and birth order. Little research, however, has investigated whether siblings' peer context is also a source of variation. The present study tested whether more popular siblings were more influential for adolescent use of cigarettes, alcohol, and marijuana. Data were obtained from sibling pairs in the National Longitudinal Study of Adolescent Health. Findings indicate that older siblings have more influence on younger sibling marijuana use when they have more friends. These findings contribute to prior work examining which siblings are more influential and highlight the need to consider siblings as part of a greater peer context.