Sibling influence on alcohol use in a young adult, high-risk sample.

OBJECTIVE: Previous research has found that siblings resemble each other in terms of alcohol use but has not examined sibling influence in young adult or high-risk siblings. The current study tested whether siblings prospectively influenced each other's alcohol use and how gender matching, age differences, and family conflict might moderate such effects.
METHOD: Data from sibling pairs (n=169 pairs) in an ongoing longitudinal study of children of alcoholics and matched controls were collected at two time points 5 years apart.
RESULTS: Older sibling alcohol use predicted younger sibling alcohol use, even after controlling for membership in a shared peer group and for parental alcoholism. However, moderator variables qualified this effect, such that older sibling influence was significant only among sibling pairs who were of the same gender, closer in age, and from higher conflict families. Younger sibling influence was significant only for sibling pairs close in age, suggesting the presence of reciprocal peer-like effects in this subgroup.
CONCLUSIONS: The current study provides evidence for sibling influence on alcohol use into adulthood, but the extent of this influence depends on sibling similarity in age and gender and on levels of family conflict. Implications for family-based theory and intervention efforts are discussed.