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Bullying among siblings linked to higher risk of developing schizophrenia, bipolar disorder

A first-ever study looks at how sibling bullying leads to the development of psychotic disorders later in life.
circa 1955: Identical twins Bobby and Jerry psych up for a game of checkers. (Photo by Nocella/Three Lions/Getty Images)

Do you have memories of fighting with your brother or sister growing up? In a study that hopefully doesn’t affect you personally, scientists found that people who experience sibling bullying are three times more likely to develop such psychotic disorders as schizophrenia or bipolar disorder in their early adulthood.

And what’s surprising, it doesn’t matter if you are the bully or the bullied — the researchers saw that the more frequently a child is involved in bullying, either as the bully or the victim — the more likely they are to get a psychotic disorder.

The research by the team at the University of Warwick was led by the psychology Professor Dieter Wolke. Their first-of-its-kind study looked at the relationship between sibling bullying and future psychotic disorders in the data from 3,600 children. The kids completed a bullying-related questionnaire when they were 12 and a standardized clinical examination for psychotic symptoms when they turned 18.

From the cohort, 664 were victimized by their bullying sibling, 486 were the bullies and 771 were both bullies and victims themselves. By the age of eighteen, 55 of the kids developed a psychotic disorder.

“Bullying by siblings has been until recently widely ignored as a trauma that may lead to serious mental health problems such as psychotic disorder, “ explained Professor Dieter Wolke. “Children spend substantial time with their siblings in the confinement of their family home and if bullied and excluded, this can lead to social defeat and self-blame and serious mental health disorder — as shown here for the first time.”

The scientists established a link between the frequency of bullying and developing disorders. And what’s profound – they saw that both the bully and the victim are traumatized by the experience. The more frequent the involvement in bullying, the more likely the child would have a psychotic disorder later. In fact, those who engaged in bullying either as a bully or victim a few times a week or month were two to three times more likely to develops such illnesses.

Victims of the sibling bullying were found to be most at risk. Kids who were victimizing both by their siblings and at school were even worse off – becoming four times more likely to develop psychotic disorders.

The study’s first author Slava Dantchev from the University of Warwick pointed how why:

“If the bullying occurs at home and at school the risk for psychotic disorder is even higher,” said Dantchev. “These adolescents have no safe place.”

He added that there is also the possibility that problems in social relationships could be early signs of a looming mental health issue rather than the cause of it.

The researchers hope that their findings will be used in developing new interventions to reduce and possibly prevent incidents of aggression within families.

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