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November 28, 2021
by Elizabeth Pratt

Differences In Brain Structure May Account For Why Some Siblings Display Antisocial Behavior

November 28, 2021 08:00 by Elizabeth Pratt  [About the Author]

Differences in brain structure among siblings could account for why some siblings develop severe antisocial behavior. 

The reason why siblings with the same upbringing and genetics can exhibit such different behavior has long puzzled psychologists, neuroscientists and researchers alike. 

Now, a team of researchers from the universities of Bath and Southampton in the UK may have an answer as to why some siblings from the same family may develop antisocial behavior when others do not. 

“We found that both the affected and unaffected siblings showed similar changes in structure in some brain regions – like the inferior parietal cortex – whereas additional brain regions were only altered in the affected siblings (the ones with Conduct Disorder). The latter brain regions are implicated in empathy and emotion / threat processing so it makes sense that they are linked to antisocial behavior, because it may be easier for you to hurt another person if you don’t care how they are feeling or you aren’t concerned about the effects of your behavior on them,” Dr Graeme Fairchild, lead author of the study and a researcher at the University of Bath’s Department of Psychology told Theravive. 

Fairchild was inspired to undertake the research when he began interacting with siblings of people with antisocial behavior. 

“When I started working with young people with severe antisocial behavior, I began to meet other members of their families and this left me wondering – why do some kids from the same family, and with the same risk factors (e.g. parental criminality or imprisonment, or parents with mental health problems), show positive outcomes while others end up in trouble with the police or commit serious crimes?” 

The researchers studied different members of the same families. Some family members had conduct disorder, and some did not have any behavioral problems. 

Conduct disorder presents as antisocial behaviors and patterns of aggressive repetitive behavior. The impact on the person with the disorder, and those around them, can be significant.

“Young people with Conduct Disorder have a host of negative outcomes, including educational failure or low educational attainment, higher rates of unemployment, relationship breakdown and mental and physical health problems in adulthood,” Fairchild said. 

“What is perhaps not fully appreciated is that their behavior can have a major impact on the rest of their family – for example, some of the young people we met had assaulted their parents or seriously damaged their own homes (kicking down doors or smashing all of the windows in the house in a rage). So there are financial and emotional costs of their behaviors on the wider family.” 

In the research published in Psychological Medicine, Fairchild and colleagues used MRI brain scans to examine the brains of 41 adolescents who had conduct disorder, and 24 siblings who had a sibling with conduct disorder but who didn’t have the condition themselves. They also did MRI scans on 38 control subjects who had no family history of conduct disorder.

They found that the people with conduct disorder and their relatives both had structural differences in the brain. 

Those with conduct disorder showed differences in their brain from their siblings. They had structural changes in the area of the brain responsible for empathy and inhibiting behavior. 

The researchers also found the siblings of those with conduct disorder had changes to the parts of the brain responsible for decision making and planning. This may be the reason why the siblings do not develop antisocial behavior despite environmental or genetic risk factors.

Conduct disorder impacts roughly 5 percent of young people between the ages of 5 and 16. That rate is higher in children in care and children who have been abused. But Fairchild says despite this, there is a lack of awareness about conduct disorder. The condition is even sometimes not recognised by psychologists. 

“I think it perhaps comes down to a class thing – Conduct Disorder is more common in people from lower social classes / high levels of social and economic disadvantage. It’s also easy to dismiss it as due to poor or permissive parenting. Lastly, we currently do not have any pharmacological treatments and young people with Conduct Disorder often don’t feel that they have a problem or don’t want to change their behavior.”

Fairchild says the research could be beneficial for young people who may be at high risk of antisocial or even criminal behavior. 

“It is useful to know what might protect some young people living in high risk families from engaging in antisocial or criminal behavior themselves. It is probably too early to use this information for intervention purposes but I think the awareness that the younger siblings of those with severe antisocial behavior are likely to show antisocial behavior as well could be helpful in terms of prioritising resources and prevention programmes for those who need them most.” 

About the Author

Elizabeth Pratt

Elizabeth Pratt is a medical journalist and producer. Her work has appeared on Healthline, The Huffington Post, Fox News, The Australian Broadcasting Corporation, The Sydney Morning Herald,, Escape, The Cusp and Skyscanner. You can read more of her articles here. Or learn more about Elizabeth and contact her via her LinkedIn and Twitter profiles.

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