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Distilled Science: Can genetics contribute to violent behaviour?

A Finnish study has found a link between criminal behaviour and gene variations, but it's not strong enough to suggest ...

AFR

A Finnish study has found a link between criminal behaviour and gene variations, but it’s not strong enough to suggest they replace free will, says a scientist.

Q: Can genetics contribute to violent behaviour?

A: Dr Malcolm von Schantz, reader in molecular neuroscience at the University of Surrey, says:

A 2014 study analysing the DNA of 895 Finnish people guilty of criminal behaviour found a link between criminal behaviour and variations in two particular genes: cadherin 13 (CDH13) – a gene involved in neural connectivity – and monoamine oxidase A (MAOA) – the “warrior gene”, which is involved in controlling levels of dopamine in the brain.

Behavioural genetics is a very interesting area of research, but also one that is full of controversies.

There is both the issue of whether a genetic association can be replicated and the issue of how to interpret it – the public will be asking themselves if the scientists are suggesting that violent offenders should not be fully accountable for their actions.

This study combines the old candidate-gene methodology, where you look at the function of known genes and make hypotheses about how they might relate to a certain disease or behaviour, and the newer genome-wide association study methodology, in which you look at millions of markers across the entire genome without any prejudice for or against any gene.

MAOA relates to two previous famous genetic association studies of violent offenders which provided a credible biological mechanism – a reduced function in an enzyme which is a target for many drugs used to treat depression and anxiety.

The pattern that is emerging is one of many genetic factors where each one has a small predisposing effect.

The authors themselves calculate that 5 to 10 per cent of violent crime in Finland is attributable to these genetic differences.

I don’t think that means that 5 to 10 per cent of crimes are individually 100 per cent attributable to these genes. Rather, it would mean they could have had an influence of 5 to 10 per cent in each case. So it is not a case of replacing free will and criminal responsibility with a genetic explanation.

But I think findings such as these may make it possible, in future, to screen people with vulnerable backgrounds and identify those who are at greater risk of becoming offenders, so they can get appropriate help before they commit any serious violent crimes.

Source: Science Media Centre

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