Older brother's influence on younger sibling's drug use.

This study examined the sibling relationship "having an older brother" and its effect on the younger sibling's stage of drug use. Sibling effects were examined in the context of the younger sibling's peer group. Data collected on 339 9th and 10th grade students indicated that domains of older sibling and peer factors each had independent lines of relationship to the younger sibling's drug use. The older brother's impact on his younger sibling's drug use varied, depending on friends' drug use, sex of the younger sibling, and whether or not the younger sibling identified with the older brother.