Siblings are more likely to take part in violent criminal behaviour if an older brother or sister did so first, particularly if they are close in age, a new study has found.

According to the findings, siblings are less likely to follow the behaviour of younger brothers or sisters.

According to Swedish and US researchers, it is widely acknowledged that violent criminal behaviour runs in families as a result of shared environmental factors, such as separated parents, poor supervision and poverty. They wanted to look into this further.

They analysed data from Swedish databases on criminal convictions. They looked specifically at age differences between siblings and the differences between being a younger or older sibling.

The study found that siblings were more likely to ‘transmit' the risk for violent criminal behaviour to younger siblings, rather than older siblings. Furthermore, the closer the siblings were in age, the greater the risk the younger one would follow in the older one's violent footsteps.

"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," the researchers commented.

They said that these findings ‘provide some insight into the possible mechanisms at work' within some families. They hope that these results may help to inform future prevention strategies aimed at reducing violent criminal behaviour.

Details of these findings are published in the journal, Psychological Medicine.