Researchers have said that if a sibling commits a violent criminal act, the risk that a younger sibling may follow in their footsteps is more likely than the transmission of that behavior to an older sibling.
In the study conducted by researchers at Virginia Commonwealth University and Lund University in Sweden, researchers examined a series of national databases from Sweden linking full sibling pairs and criminal conviction.
The team conducted two analyses - one that looked at age differences in siblings, and one that examined the difference in the risk of being a younger sibling versus an older sibling of a proband with violent criminal behavior.
Researchers found that older siblings more strongly "transmit" the risk for violent criminal behavior to their younger siblings, rather than vice versa. The team also found that the closer in age that siblings are, the greater the risk for the transmission of violent behavior.
The authors write, "Because older siblings often exert more influence on siblings than younger, the risk for violent criminal behavior should be greater when the older sibling has violent criminal behavior as compared to the younger sibling. However it is not just mere closeness in age, but rather the nature of the sibling relationship that often occurs when siblings are closer in age."
First author Kenneth S. Kendler, M.D., director of the VCU Virginia Institute for Psychiatric and Behavioral Genetics, said their findings strongly support the importance of familial-environmental influences on violent criminal behavior and provide some insight into the possible mechanisms at work.
The study has been published online in the journal Psychological Medicine.