Genetics underpin bullying victimisation influence on paranoia

By Eleanor McDermid, Senior medwireNews Reporter

Bullying victimisation in childhood may indicate genetic risk for later psychosis, rather than being an environmental trigger, say UK researchers.

The team’s study of 4826 twin pairs revealed that bullying victimisation was most strongly, although only modestly, associated with paranoia in adolescence, but that this association was “explained almost in its entirety by shared genetic influences.”

“These findings suggest that in childhood there may be inherent genetic predispositions that orientate children’s behavior and thinking styles in such a way that it makes them jointly vulnerable to being victims of bullies and adopting paranoid thinking styles”, say Sania Shakoor (University of London, UK) and study co-authors.

They speculate that a negative attribution style is one factor that could be caused by genetics and account for both bullying victimisation and paranoid thinking.

The researchers examined the incidence of bullying victimisation at the age of 12 years – at the transition between schools in the UK – and psychotic experiences at the age of 16 years. They found that bullying explained around 6% of the variance in paranoia and between about 1% and 3% of the variance in hallucinations, disorganization and parent-rated negative symptoms. Bullying victimisation explained little or none of the variance in anhedonia and grandiosity.

“These findings emphasize the value of exploring associations with specific [psychotic experiences], rather than assuming they can be clumped together or limiting investigations to only some forms of [psychotic experiences]”, say Shakoor et al.

Differences between monozygotic and dizygotic twins in the sample allowed the team to determine that genetic factors explained 35% and 52% of the variance in bullying victimisation and paranoia, respectively, with environmental factors accounting for 39% and 48%.

However, genetic factors accounted for almost the entirety of the association between bullying and paranoia, with environmental factors explaining a small, nonsignificant amount. This remained the case after the team had accounted for emotional problems, bullying victimisation at age 16 years and cannabis use.

“It can seem counterintuitive at first that an experience, such as being bullied, is partly heritable”, write the researchers in Schizophrenia Bulletin. “However, risk of bullying victimization is known to be influenced by characteristics in the child who is bullied, such as temperament and self-esteem, which are themselves heritable.”

They note that, if the associations persist into adulthood, doctors should be alert for paranoid symptoms in people with a history of bullying victimisation.

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