Professor Jari Tiihonen and colleagues analysed the genes of 895 Finnish individuals sentenced for crimes and found a possible link between violent offences and the MAOA gene. The association was strongest in individuals with repeated violent offences. The research was published in the renowned journal Molecular Psychiatry.
Previous research has linked some genes to violent crime, including a variant of the MAOA gene that contributes to a decreased recycling of the neurotransmitter dopamine. However, earlier studies on the association between MAOA and violent behaviour have produced conflicting results, and so far no study has been able to identify a link between genes and repeated violent behaviour or extremely violent offences, such as homicide.
Tiihonen’s research team also discovered that a variant of the CDH13 gene, involved in neural connectivity, was more common in extremely violent offenders than in the control group. Previous research has already linked this gene variant to impulsive behaviour.
The research did not find any substantial presence of either MAOA or CHD13 in non-violent offenders.
The authors suggest that the MAOA genotype may result in higher aggression levels during intoxication, increasing the risk of violent behaviour.
The majority of violent offences are committed by a small group of repeated offenders. The authors estimate that the two genotypes may account for some 5–10 per cent of violent offences in Finland.
“The Nordic principle of forensic psychiatry maintains that assessments of criminal responsibility are not based on any risk factors, such as genotype, and the focus is, instead, on the actual mental capability of the offender,” reminds Jari Tiihonen.
“The findings are interesting as they increase our understanding of the neurobiological mechanisms behind aggressive behaviour, but they cannot be used for purposes of screening or crime prevention. The CDH13 gene variant is very common in the population, and around one third of people have it,” says Professor Tiina Paunio from the National Institute for Health and Welfare (THL). Paunio was in charge of the genetics analyses.
The study was a collaboration between the Niuvanniemi Hospital, the Swedish Karolinska Institutet, THL, the FIMM Institute for Molecular Medicine Finland at the University of Helsinki, the University of Eastern Finland, and the Finnish Criminal Sanctions Agency. Other researchers participating in the study represented, among other institutes, the Harvard University, the Stanford University, the Wellcome Trust Sanger Institute, and the US National Institute on Alcohol Abuse and Alcoholism.
J Tiihonen, M-R Rautiainen, H M Ollila, E Repo-Tiihonen, M Virkkunen, A Palotie, O Pietiläinen, K Kristiansson, M Joukamaa, H Lauerma, J Saarela, S Tyni, H Vartiainen, J Paananen, D Goldman & T Paunio. Genetic background of extreme violent behavior. Molecular Psychiatry, advance online publication, October 28, 2014; doi:10.1038/mp.2014.130
For further information, please contact:
Jari Tiihonen (Karolinska Institute / Niuvanniemi Hospital / University of Eastern Finland)
tel. +358 50 3418363
Tiina Paunio (THL and University of Helsinki)
Researcher in charge of the molecular genetic analysis