Is There a Criminal Gene?

Our genes are a strong determinant of who we are as an individual, whether that’s our biological make up or aspects of our personality. However, the debate of whether genes underpin criminal behaviour or whether it is a result of the social environment, is an ongoing debate which researchers continue to investigate.

Although there is no clear explanation of why people turn to crime, researchers have now found a common trait amongst many inmates. Recent research has found that antisocial personality disorder (ASPD) was found in 40-70% of prison populations, in comparison to just 1-3% in the general population.

ASPD is a psychological condition which is associated with manipulation, aggression and a general disregard for rules and other people. Symptoms develop in a person’s late teens and improve by the time the individual reaches their early 40s, suggesting that even though there is a strong biological component, effective therapies may be related to the ‘nurture’ side of the nature-nurture debate.

A genome wide study of Finnish prisoners found that from 794 prisoners, 568 of them were categorised as being positive for ASPD. A further analysis found that two genes in particular, ‘cadherin 13’ (CDH13) - a gene involved in neural connectivity and ‘monoamine oxidase A’ (MAOA), a controller in dopamine levels in the brain, were associated with criminal behaviour. However, as with all research we must tread on the findings carefully, as there are many other external factors which need to be considered.

Twin studies have also been conducted to assess the genetic link. One study conducted looked at 32 MZ twins who were reared apart, thus eliminating environmental factors. The results showed that both childhood and adult antisocial behaviour, had high heritability involved (Joseph, 2001). However, as with all twin studies we need to consider why the concordance rates between twins is not 100%...

Moving away from finding a direct link between genetics and criminality, researchers have started to investigate whether there is a link to depression and criminality. An observational study conducted in Sweden found that there was a strong association between violent crime and depression (Fazel et al, 2015). Patients with depression suffer from low levels of Serotonin (5-HT). Research shows that 5-HT plays a role in the control of mood, depression, and even suicide. In regards to a genetic link for depression, if someone has a parent or sibling with major depression, that person has a 2 or 3 times greater risk of developing depression compared with the average person (or around 20-30% instead of 10%).

As always in psychology, there is no definitive answer to whether crime can solely be explained by genetics, or is an interaction of genes and the environment.

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