19 Jun “Bad Genes” plus “Bad Environment” Lead To Brain Abnormalities in Youth With Conduct Disorders
MedicalResearch.com Interview with:
Dr. Luca Passamonti MD
Department of Clinical Neurosciences
University of Cambridge
MedicalResearch.com: What is the background for this study?
Dr. Passamonti: We wanted to study if the brain of young people with two different forms of conduct disorder (CD) (https://en.wikipedia.org/wiki/Conduct_disorder), a neuropsychiatric disease associated with severe and persistent antisocial behaviors (weapon use, aggression, fire-setting, stealing, fraudulent behavior), was different from that of young peers with no such abnormal behaviors.
There is already evidence that conduct disorder may have a biological basis (i.e., reduced levels of cortisol under stress) and brain alterations but a whole “map” of the brain in conduct disorder studying cortical thickness was never been done before.
MedicalResearch.com: What are the main findings?
Dr. Passamonti: We found differentially abnormal inter-regional correlations in cortical thickness in both forms of conduct disorder. Inter-regional correlations mean how much a cortical region (a piece of the brain with a specific function) is SIMILAR to a different piece of the brain in terms of thickness (cortical thickness). Literally how thick the cortex is and how the thickness in one part is similar to the thickness in another part. The thickness of the cortex depends on a series of things including number of cells, internal connections, synapses, etc. With magnetic resonance imaging we can’t measure this microscopic phenomena so the cortical thickness is just an indirect measure of several things happening in the cortex at the molecular and cellular level.
Youths with antisocial behavior with childhood-onset (early starters) have MORE pieces of the brain similar to each other than normal youths in term of thickness. In contrast, youths with antisocial behavior with adolescent-onset (later starters) have LESS pieces of the brain similar to each other than early starters and normal people. This pattern of results is very very interesting and can be related to specific neurodevelopment patterns happening during distinct time-windows of brain development.
In other words, if something goes wrong developmentally during childhood you may end up having a form of antisocial behavior which is different to a development problem that is happening during adolescence, due to the very different nature of the developmental mechanisms intervening during childhood and adolescence (for example cellular and synaptic growth during childhood and synaptic “pruning” during adolescence).
Another important issue to mention regards the causes of the developmental effects we’re seeing here.
Well, neuroimaging can’t do causality at all, it’s just a “snapshot” of what’s going on (in this case wrongly) in the brain at a specific time point. But we believe that a combination of “bad genes” (unknown at the moment) plus very bad environment (child abuse, neglect, etc, maternal drinking & smoking, etc.) can lead to the sort of neurodevelopmental problems that we’re seeing in our participants.
MedicalResearch.com: What should readers take away from your report?
Dr. Passamonti:: Conduct Disordered young people may have a rather serious brain developmental problem. We don’t know the cause of it but it is likely that a combination of “bad” genes and “bad” environment leads to the brain abnormalities that we do see. Also the developmental “window” in which these abnormalities take place can lead to different forms of CD depending on when the problem arise. In other words, CD developed during childhood is very different than conduct disorders developed during adolescence in terms of brain abnormalities.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Dr. Passamonti: We need to run “longitudinal” studies which means that we need to follow-up our participants and repeat brain scans every year (for example) to see how the brain abnormalities that we’ve detected change in relation to the change in antisocial behaviors. Antisocial behaviors are not fixed or necessarily permanent problems so given the presence of brain plasticity it is possibile that they depend on how much the brain problems evolve and how long the last or resolve. For example, some youths go on and develop very severe antisocial personality disorders in adulthood, while others become less antisocial, aggressive, and somehow “normalize”. So the question is how this behavioral variability relate to variability in the brain? Another very interesting scientific question to answer in the future would be whether people at very high risk of developing antisocial behavior (but who have not developed it yet) already show the brain “signatures” that we have identified in this study. This will tell us how early these brain problems appear.
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G. Fairchild, N. Toschi, K. Sully, E.J.S. Sonuga-Barke, C.C. Hagan, S. Diciotti, I.M. Goodyer, A.J. Calder, L. Passamonti.Mapping the structural organization of the brain in conduct disorder: replication of findings in two independent samples. Journal of Child Psychology and Psychiatry, 2016; DOI: 10.1111/jcpp.12581
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