If you bully your sibling, they’re three times more likely to develop this mental disorder

Most people are guilty of bullying our siblings to a certain extent. Few people can say that they’ve never been responsible for starting up a fight and then stepping back and watching in glee as their sibling takes the brunt of the punishment from mum or dad. But the question is: when does sibling rivalry cross the line? At what point does it go past rough-housing your brother and frantically apologising before mum enters the room into genuine harmful bullying?

It’s a fine line and one that we all need to watch out for, given the fact that people who were bullied by siblings during childhood are up to three times more likely to be diagnosed with a psychotic disorder in future life. A new study by the researchers at the University of Warwick recently revealed that those who are tortured by their brothers and sisters growing up are often left traumatised and can develop disorders like schizophrenia by the time they are 18 years old.

Psychotic disorders are defined as severe mental disorders that cause abnormal thinking and perceptions. Typically, people with severe mental disorders lose touch with reality, with two of the main symptoms being delusions and hallucinations. In addition, sufferers often experience severe distress, changes in behaviour and mood, and have a much-increased risk of suicide and health problems.

Unsurprisingly, the study also found that the more often a child got bullied, the higher their likelihood of developing a severe mental disorder that caused abnormal thinking and loss of touch with reality was. While kids who fall victim to sibling bullying several times a week or month are two to three times more likely to develop a psychotic disorder such as schizophrenia, for those bullied both at home and in school, their odds were even more dramatic at four times as high.

Senior author Professor Dieter Wolke, from the University of Warwick’s Department of Psychology, said: “Bullying by siblings has been until recently widely ignored as a trauma that may lead to serious mental health problems such as psychotic disorder. ‘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 study worked with almost 3,600 children from the Avon Longitudinal Study of Parents and Children, who completed a detailed questionnaire on sibling bullying at the age of 12, with the same individuals filling out a standardised clinical examination assessing psychotic symptoms when they were eighteen years old.

Of the adolescents who took the test, 664 were victims of sibling bullying, 486 children were pure bullies to their siblings and 771 children were both bullies and victims (they were both victimised by their siblings and bullied their siblings), at age twelve. In the end, researchers found that 55 of the 3,600 children taking part had developed a psychotic disorder by the age of eighteen, discovering found that the more frequently children are involved in sibling bullying – either as bully, victim, or both – the more likely they are to develop a psychotic disorder.

Lead author Slava Dantchev, also from the University of Warwick, added her own comments on the issue, stating: ‘If the bullying occurs at home and at school the risk for psychotic disorder is even higher. These adolescents have no safe place. Although we controlled for many pre-existing mental health and social factors, it cannot be excluded that the social relationship problems may be early signs of developing serious mental health problems rather than their cause.”

This isn’t the only evidence that we have that suggests that your relationship with your siblings massively affects you in future life. In fact, according to researchers at Brigham Young University, brothers and sisters can shape a person’s life even more so than a parent. Apparently having a loving sibling of either gender promoted good deeds, such as helping a neighbour or watching out for other kids in your class at school. The 2010 study even claimed that the relationship between sibling affection and good deeds was twice as strong as that between parenting and good deed.

“Even after you account for parents’ influence, siblings do matter in unique ways,” said lead author Padilla-Walker in 2010. “They give kids something that parents don’t.”

This positive influence was particularly noticeable between sisters, with statistical analyses showing that having a female sibling protected adolescents from feeling lonely, unloved, guilty, self-conscious and fearful. Surprisingly, it didn’t matter whether the sister was younger or older, or how far apart the siblings were in age.

So, we knew that our relationships with our siblings could have a big effect on us, but not many people would have guessed that they would have such a profound influence on the way our lives are shaped. For either better or worse, this study suggests that we are the people who make our siblings who they are, and if we want them to grow up to be happy and healthy individuals, kindness and understanding is the way forward.