Being bullied by a sibling may increase a child’s risk for depression when they are older, BBC News reported.

Researchers at Oxford University surveyed 7,000 12-year-olds and asked if they had experienced a sibling saying hurtful things, hitting, ignoring or lying about them. Six years later, they followed up with participants at age 18 to assess their mental health.

The 786 children who admitted to being bullied by a sibling several times a week were found to be twice as likely to suffer from depression, self-harm and anxiety, compared to those who were not bullied. Depression in this group was reported at 12.3 percent, self-harm at 14 percent and anxiety at 16 percent.

Of the children who said they had not been bullied by a sibling, 6.4 percent had depression scores in the clinically significant range at the six-year follow-up, 9.3 percent suffered anxiety and 7.6 percent had self-harmed within the previous year.

"We are not talking about the sort of teasing that often goes on within families, but incidents that occur several times a week, in which victims are ignored by their brothers or sisters, or are subjected to verbal or physical violence," said lead author Dr. Lucy Bowes, of the department of social policy and intervention at the University of Oxford.

Girls were more likely to be victims of sibling bullying than boys – particularly in families with three or more children – and older brothers were often the ones doing the bullying. On average, bullying victims said the behavior had started at eight years old.  

"We need to change the conversation we have about this. If it occurred in a school setting there would be repercussions,” Bowes said. "It may be causing long-term harm. We need to do more research, but we also need parents to listen to their children.”

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