Brain differences seen in children with conduct disorder depend on abuse history

Key findings:

• Study finds significant differences in ‘white matter’ in the brains of young people with conduct disorder (CD) who have been abused and those who have not.
• This study is the first to look at differences in white matter between youth with CD who have a history of childhood abuse and those who do not, and to compare both  groups to healthy controls.
• The white matter of abused youth with CD did not  differ from healthy controls, but white matter of non-abused youth was significantly altered in key pathways within the brain.
• The  study’s authors speculate that for some individuals there may be a genetic basis for CD, while for others the disorder may result from childhood abuse. If so, different treatments may be appropriate depending on the origin of the disorder.
• CD is a psychiatric condition, usually diagnosed in children and adolescents, related to severe antisocial behaviour (e.g. fighting, bullying, truancy and theft).

Body text:

Young people who are diagnosed with conduct disorder show significant differences in their brain structure depending on whether or not they have also suffered childhood abuse, according to new research led by the University of Bath in the UK. This finding suggests the combined effects of childhood maltreatment and conduct disorder impact the architecture of the brain.

The study’s authors believe there may be implications for the way children and adolescents with conduct disorder (CD) should be diagnosed and treated.

Until now, no diagnostic distinction has been made between young people with CD who have been abused and those who have not. However, if future research corroborates the findings of the new study, there may be good reason for clinicians to distinguish between people with CD who have suffered maltreatment in their early years from those who have not.

Dr Sophie Townend, a researcher in the Psychology Department at the University of Bath and lead author of the study, said: “Our findings suggest there are differences in brain structure between youth with conduct disorder depending on their abuse histories, which may suggest there’s a distinct pathway from abuse to developing this disorder.

“If this is true, we now need to consider whether there are clinical and neuropsychological differences between those with and those without a history of childhood abuse, and whether their treatment responsiveness differs. It may be that differentiating between these two groups allows us to develop more effective treatments.”

Conduct disorder

CD is associated with the highest burden of any mental disorder in childhood and is found in an estimated 3% of children and adolescents worldwide, yet its neurobiology remains unclear. Neurobiology is the branch of biology concerned with the brain and the central nervous system, and how these influence thought and behaviour.

CD is a psychiatric disorder characterised by severe and persistent aggressive and antisocial behaviour, such as fighting, rule-breaking and bullying. The disorder puts a young person at risk of future delinquency, substance abuse and mental illness. It often leads to antisocial personality disorder and criminality in adulthood.

White matter vs grey matter

The new study found differences in ‘white matter’ between individuals with conduct disorder (CD) who have been abused and those who have not. White matter represents the neural pathways along which electrical signals pass as one brain area communicates with another.

Earlier work, also led by the University of Bath, has shown key differences in ‘grey matter’ (the nerve cell-rich regions of the brain) between individuals with CD and those without the disorder. The areas of grey matter most impacted were found to be those involved in emotion processing, decision-making and reinforcement learning (the sort of learning that teaches healthy individuals to avoid behaviours that receive negative feedback).

The same study into grey matter also found that individuals with CD who had experienced abuse showed more pronounced changes in the physical structure of their brains than those with CD who had not been abused, when both groups were compared to typically-developing children without CD.

The new study is the first to look specifically at differences in white matter between youth with CD who have a history of childhood abuse and those who do not, and to compare individuals in these two sub-groups to healthy controls.

The researchers found that, unlike with grey matter, the white matter of abused individuals with CD does not differ from that of healthy controls. By contrast, youth with CD who have not been abused show significant alterations in their white matter.

Although the reasons for these changes in non-maltreated individuals remain unclear, the study’s authors speculate that a genetic basis for CD in some people may be responsible for these structural differences.

Dr Townend said: “In other words, people may end up at the same clinical end-point but their condition may have a different origin or cause.

“Some may have conduct disorder because they were born predisposed to have altered white matter development, which ultimately leads to behaviours that manifest as conduct disorder, and others may have it because they experienced maltreatment while their brains were still forming, leading to structural grey matter changes, and the development of the same disorder.”

The new study’s international team of researchers found a second difference between the brains of people with CD: those who have been maltreated exhibit changes in the superior longitudinal fasciculus (a white-matter pathway involved in emotion processing, learning and social cognition) when compared to their non-maltreated counterparts.

“This appears to support our hypothesis that abuse can lead to key changes in the brain, and suggests that even though the maltreated and non-maltreated subgroups share the same diagnosis, they differ from one another in white matter,” said Dr Townend.

Professor Graeme Fairchild, also in the Department of Psychology at Bath and senior author of the study, said: “This study provides more evidence that maltreatment of children matters and that even the biology of the brain is different according to whether you have experienced maltreatment or not.

“We haven't established a causal link between maltreatment and CD in this study, but this is an interesting piece of the puzzle and supports our hypothesis that there are key differences between those with and those without a history of abuse. This could suggest that there are different pathways to the same condition – one that is more environmental and one more genetic.

"The implications of this study for differentiating between maltreated and non-maltreated kids with conduct disorder are some way off, but we are now able to present a clear case for future research to consider the impact of abuse and maltreatment on their findings, which may ultimately lead to a better understanding of the disorder.”

Brain scans

For the new study, the brains of 100 children and adolescents with CD, 39 of whom had a history of abuse, and 169 typically-developing youth, were scanned in a magnetic resonance imaging (MRI) scanner. Maltreatment was assessed by asking parents whether their child had ever experienced physical or sexual abuse, and allowing for other disclosures of adverse experiences and maltreatment.

The scans looked at white matter by using a technique called diffusion tensor imaging, or DTI. This technique allows researchers and clinicians to measure white matter by measuring how water molecules move in the brain.

The authors of this study emphasise that childhood maltreatment can increase a person’s risk of developing mental health outcomes beyond conditions such as PTSD, and they call for more research in this field.

“It’s vital for us to extend our understanding of the effects of abuse at the brain level, as many studies show that experiencing abuse or maltreatment can increase the child’s risk of developing mental health problems including CD.” said Dr Townend.

This study also involved researchers from the Universities of Birmingham (UK), Basel (Switzerland), Goethe University Frankfurt (Germany), and RWTH Aachen University (Germany), among others.