Structural differences in the brain may explain why siblings differ in the risk of developing a conduct disorder

Structural differences in the area of ​​the brain responsible for decision-making could explain why two siblings living in the same family might differ in their risk of developing the conduct disorder.

Psychologists and neuroscientists have long wondered why siblings with seemingly the same upbringing and genetic makeup might differ so significantly in behavior: how some young people growing up in families with antisocial or criminal behavior manage they keep out of trouble (the white sheep of the family)?

Researchers at the Universities of Bath and Southampton have studied this question by studying different members of the same family, some with mental conduct disorders and others without behavioral problems.

Conduct disorder is characterized by repetitive patterns of aggressive and antisocial behavior. This entails substantial personal and financial costs for the individuals concerned, their families and society in general and is one of the most common reasons for referral to child and adolescent mental health services in the UK.

Conduct disorder has a prevalence rate of around 5% among young people aged 5 to 16, although there is a strong social class gradient: a 2004 survey reveals nearly 40% of children caught. in charge, those who have been abused or entered on backup registers. , had a conduct disorder. Despite all this, the general knowledge of the disease remains low and it is not recognized by many psychologists or psychiatrists.

The new study, published today in the journal Psychological medicine, sought to understand the underlying mechanisms that could determine a person’s risk of developing the disease. The international team, including Dr Graeme Fairchild of the University of Bath, performed MRI scans of the brain on 41 adolescents with conduct disorders, 24 unaffected siblings (who had siblings with conduct disorders conducts but did not themselves present the disorder) and 38 typically developing as controls without a family history of conduct disorder.

Their analysis found that young people with conduct disorders and their families both had structural differences in the brain – in a part of the brain called the lower parietal cortex. However, there were also structural changes in the brain that were group-specific conduct disorders in areas of the brain responsible for empathy and cognitive control / inhibitory behavior that were not found in siblings. not affected.

In addition, the researchers also found changes in the prefrontal cortex, an area of ​​the brain involved in planning and decision making, that were specific to the group of unaffected siblings – which may explain why they are protected against antisocial behavior despite growing up with one or the other environment. or genetic risk factors for conduct disorder. Previous work by the same team found that despite differences in antisocial behavior between siblings, people with conduct disorders and their unaffected siblings had difficulty recognizing emotional facial expressions.

Our study aimed to understand the root causes of conduct disorder, in particular what differentiates family members in their antisocial behavior and are there genetic markers for conduct disorder risk in the brain.

Dr Graeme Fairchild, Department of Psychology, University of Bath

“This is one of the first family studies on conduct disorders and it confirms that the brain is important in distinguishing members of the same family who are at greater risk of developing antisocial or criminal behavior.”

“Interestingly, while our previous work has shown common impairments between affected and unaffected siblings in recognizing facial expressions, this study suggests that major differences in behavior can be determined by small changes in the part of the body. brain responsible for executive functioning or decision making. These differences could make some siblings more prone to risky behaviors and should now be the subject of future study. “

The authors hope their findings may ultimately help guide early interventions for younger siblings of adolescents with conduct disorders, helping them access help and treatment at an earlier age. .

Source:

Journal reference:

Fairchild, G., et al. (2021) Neuroanatomical markers of familial risk in adolescents with conduct disorder and their unaffected relatives. Psychological medicine. doi.org/10.1017/S0033291721003202.

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