Sibling animosity may be a universal truth, but that doesn't mean it is well understood. In a first attempt to link behavioral problems in early adulthood to the relationship with a brother or sister, researchers found that boys with older siblings who were critical of them were more likely to be arrested or to abuse drugs and alcohol.
In the study, 20-year-old boys with older siblings who had negative attitudes toward them were also more likely to associate with deviant peers and have sexual intercourse at a younger age than were boys with noncritical siblings. They exhibited the same antisocial behavior two years later.
The study, published in the Journal of Family Psychology (2003), required 73 men and women to describe their relationship with a younger brother. These findings do not imply that criticism causes deviance: Indeed, the siblings could have been highly critical because their brothers' behavior was problematic. But they do illustrate the potentially harmful impact of sibling interaction, says Bernadette Bullock, Ph.D., a research scientist at the University of Oregon's Child and Family Center and co-author of the study.