Anti-social behaviour in some children could be the result of their genetic make-up, a study says.
Genes and the environment both play a role in behaviour
UK research on twins suggests children with early psychopathic tendencies, such as lack of remorse, are likely to have inherited it from their parents.
These young children may also display inherited anti-social behaviour, the Institute of Psychiatry team found.
But environmental factors are also important and, if favourable, could act as a buffer, they stressed.
And anti-social behaviour in children with no psychopathic tendencies is likely to be down to mainly environmental factors, they believe.
Previously, the same researchers had found boys who had a particular version of a gene were much more likely to display antisocial behaviour if they suffer maltreatment when young.
In the current study, published in the Journal of Child Psychology and Psychiatry, Professor Terrie Moffitt and colleagues from King's College, London, followed 3,687 pairs of seven-year-old twins.
Twins are often used to investigate inherited traits because identical twins share the same genes, and therefore the same inherited influences, whereas non-identical twins do not.
The researchers used teacher ratings of anti-social behaviour and psychopathic tendencies - lack of empathy and remorse - to rank the twins into groups.
Those falling in the top 10% for anti-social behaviour were split into two groups - those with and without psychopathic tendencies.
Analysis showed that anti-social behaviour was only strongly inherited in the psychopathic children.
Lead investigator Dr Essi Viding said: "The discovery that psychopathic tendencies are strongly heritable suggests that we need to get help for these youngsters early on.
"Any behaviour is influenced by multiple genes and an unlucky combination of genes may increase vulnerability to a disorder.
"However, strong heritability does not mean that nothing can be done. Children are open to protective environmental influences early in life and these influences can buffer the effect of genetic vulnerability."
Professor Marian Fitzgerald, visiting professor of criminology at the University of Kent, said this early-onset anti-social behaviour was different from that seen more commonly among teens aged 15-17.
"Most people who get involved in crime and anti-social behaviour are not genetically predisposed.
"A lot of kids get swept up in their teens and there are many social, economic and environmental factors involved. Most grow out of it.
"Obviously, individuals with genetic factors that predispose them to this behaviour will be more at risk. But tackling this small number of people will not make a big difference for society.
"What is important is to look at early interventions - family support, economics, improving neighbourhoods, pre-school education and so on. These are critically important."