Conclusion
This study indicates that, from a cross-sectional perspective, adolescents' smoking habits are much more strongly associated with their peers' smoking habits than with their parents or siblings' smoking habits. From a longitudinal perspective, however, it seems that parents' SES and parental and older siblings' smoking behaviours are of enduring importance for smoking among adolescents. Over time, parents' SES both directly and indirectly predicts smoking initiation and development among children. Although the direct association between parents' SES diminishes as adolescents grow older, the combination of parental and sibling influence is important. There are calls for more specific anti-smoking interventions that specifically target at-risk individuals and smokers, and our results lend support to interventions that address both distal and proximal factors.