December 18, 2017

expert reaction to study investigating brain lesions and criminal behaviour

In new research, published in PNAS, scientists explore whether there is an association between brain lesions and whether they contribute to criminal behaviour.

Prof. Huw Williams, Professor in Clinical Neuropsychology and Co-Director of the Centre for Clinical Neuropsychology Research (CCNR), University of Exeter, said:

“There have been a number of high quality studies showing an increased risk of crime after brain injury – usually about twice the risk compared to non-injured. We also know that more than half of people in prison have a history of head injury. With one or two in ten having had relatively serious injuries.

“This study is fascinating and important as it shows how particular types of brain lesions may have contributed to criminality in people who were not known to have a tendency to offend before they suffered the lesion. The key point there is ‘might contribute’ as such lesions would not likely be a direct cause and this specific study could not confirm causality. The participants had been neuro-imaged and psychologically tested in other studies. Lesions were in brain systems linked to understanding the perspective of others. Such issues are very common in offenders. This study therefore makes us much better able to understand the mechanism by which brain trauma may contribute to crime. It also gives us suggestions for how we can improve treatments to reduce such risk.

“However a key weakness is that these cases were selected from published studies, which makes one wonder about those with such lesions who didn’t go on to offend. Based on these caveats, I would describe this research as preliminary and we would need more controlled studies- with a greater number of participants- to draw stronger conclusions.”

Prof. Masud Husain, Professor of Neurology & Cognitive Neuroscience, University of Oxford, said:

“These provocative findings provide further support for the view that criminal behaviour can emerge from disruption to specific brain networks. Of course, there can be many other reasons why people might turn to criminality but most neurologists are familiar with patients whose decision-making, value judgments and ‘moral compass’ change following the onset of a brain disease.

“The new data presented here suggest that changes which lead to criminal behaviour occur with dysfunction of specific networks – wiring pathways that connect specific parts of the brain.

“We need to be cautious though about some aspects of the study. It is retrospective and dependent on cases reported in the literature where there was evidence of changes on brain scans. Only forty such cases were found, and of these only 17 had a history which suggested that the behavioural change occurred after the development of the brain lesion. So the analyses were performed on very small sample sizes.”

Dr Graeme Fairchild, Reader in Developmental Psychopathology, University of Bath, said:

“The methods used in this study seem very indirect – the authors are simply going from images of brain lesions published in other studies, and then relating the reported location of these legions to patterns of brain connectivity in healthy, non-brain-damaged people.  I think the casual reader might have the impression (from the brain images, etc.) that the authors actually studied these patients and scanned their brains themselves, but this doesn’t seem to be what happened.  It is also questionable how much the information about temporal relationships between brain damage and criminal behaviour can be trusted – given that criminals are far more likely to suffer brain injuries than the general population because they behave irresponsibly or dangerously (driving while drunk or sustaining head injuries due to fighting).  I couldn’t see anything in the article about the causes of the brain damage – but this is clearly an important issue.  If, as in the example they give, someone develops a brain tumour and then starts behaving in a violent way, this is more convincing evidence for a causal link between brain damage and criminality, than if they suffer a head  injury due to being in a fight, and then continue to be violent.  This is still an interesting paper but it would have been better to actually scan the 17 (or 40) patients’ brains or follow up a sample of patients with brain injuries sustained in road traffic accidents, combat situations, etc., to see which ones become violent/criminal and whether this relates to the site and extent of the damage.”

Prof. Seena Fazel, Professor of Forensic Psychiatry, University of Oxford, said:

“Despite its intuitive appeal, it has been difficult to pin down specific areas of the brain that are associated with criminality. This is partly because such brain lesions may be incidental, reflecting, for example, accident-proneness in individuals who also happen to commit criminal acts. In such cases, what links the brain lesions and the subsequent crimes may be a personality trait such as impulsivity, which is only apparent under certain conditions (and which will not be found by looking at brain lesions). It may also be that what links brain lesions and crime is whether an individual consumes certain illegal drugs or excessively drinks alcohol, which will increase your chance of having serious accidents, and also lead some individuals to commit crimes.

“This particular study relied on searching the literature to determine whether there were any brain lesions that were consistently associated with crime. The study design cannot establish a causal relationship. It relied on identifying brain lesions in 17 published cases, which is a small number, and testing them in a further 23 published reports. In a comprehensive review of the literature that came out earlier this year that we conducted (Lamsma, Psychiatry Research: Neuroimaging 2017 – http://www.psyn-journal.com/article/S0925-4927(17)30039-2/abstract [open access]), we identified 35 studies that looked at brain regions that were associated with violence, which was based on 1288 participants. Importantly, we found the most common finding was that there was no difference in grey matter volume in individuals who had violent outcomes compared to control populations, even in the prefrontal cortex and temporal lobes, which have been highlighted in the current study by Darby and colleagues.

“This underscores the importance of interpreting individual studies in the context of the wider literature.  In addition, there are limitations in drawing on single case reports, as has been done here, as these reports tend only to be written up and also published if a positive association with a brain lesion is found. It is likely, however, that there are many other single cases that found no such association, and were never written up for publication.”

* ‘Lesion network localization of criminal behavior’ by Darby et al. published in PNAS  on Monday 18 December. 

Declared interests

Prof. Huw Williams: No conflicts of interest.

Prof. Masud Husain: No conflicts of interest.

Dr Graeme Fairchild: “My research is funded by the European Commission, the Medical Research Council, and the Waterloo Foundation, but none of this funding relates directly to my capacity to comment on this study.  My research interests are in the biological basis of antisocial behaviour in children and young people, and particularly the causes of sex differences in antisocial behaviour and violence – so some way removed from the topic of this research.”

Prof. Seena Fazel: No conflicts of interest.