- Good parenting could prevent antisocial behaviour in
people genetically prone to aggression, findings in animals suggest.
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- Past studies have linked certain genes with aggressive
behaviour in both humans and animals.
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- Dr Stephen Suomi from the US National Institutes of Health
said studies in monkeys show a nurturing environment can buffer the effect
of these genes.
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- His research will be published later this year in Biological
Psychology.
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- Previous research has linked low levels of brain chemicals
such as serotonin and monoamine oxidase A (MAOA) with aggression in humans
and animals.
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- The levels of these chemicals are controlled by genes.
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- Scientists know some people have genes that make them
susceptible to aggression and anti-social behaviour.
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- People hospitalised for depression and other psychiatric
disorders have been found to have a genetic make-up that means they have
lower levels of serotonin or MAOA, for example.
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- But environmental factors such as upbringing are also
known to be important in behaviour.
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- Dr Suomi, from the National Institute of Child Health
and Human Development, and colleagues studied a large population of wild
rhesus monkeys, which are closely related to humans in terms of genes.
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- The monkeys were divided into groups based on their observed
aggressive behaviours. About 5-10% of the monkeys showed excessive levels
of violent, antisocial behaviour.
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- Aggression
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- These aggressive monkeys had the least serotonin levels
in the brain, while the least aggressive had the most.
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- As previously shown, the serotonin levels, which are
controlled by genes, were linked to the monkey's genetic make-up.
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- In another study, Dr Suomi looked at the effect of rearing
on young monkeys genetically prone to aggressive behaviour.
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- >From birth to six months of age, the monkeys were
reared either in a nurturing, supportive way by their mother or were left
with their siblings to fend for themselves.
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- As expected, the monkeys left with their siblings had
low levels of serotonin and displayed aggressive behaviour.
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- But the monkeys who had been reared by their mothers
had normal levels of serotonin and displayed normal behaviour despite being
genetically prone to aggression.
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- Dr Suomi said: "It's a gene-environment interaction.
There's a buffering effect of good mothering.
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- "Good mothering is very important and may actually
protect individuals who have genes that make them vulnerable," he
said.
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- But he cautioned that the findings were in animals and
could not be generalised to humans.
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- "We have to be careful about making comparisons
across species. All we have demonstrated is an interaction between one
particular gene and the environment.
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- "There could be many, many more," he said.
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- Dr Suomi is doing more research looking at how positive
rearing might protect against aggression in monkeys genetically prone to
this behaviour.
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- Nature and nurture
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- Professor Donald Pfaff, from Rockefeller University in
the US, who has conducted similar research into aggression in animals,
said more research was needed.
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- "It's a very big puzzle at the moment. There are
over 50 genes that contribute to the arousability of the brain," he
said.
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- Dr Clio van Velsen, consultant psychiatrist in forensic
psychotherapy for East London and the City Mental Health Trust, said: "There
is no longer this simplistic divide between nature and nurture.
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- "This need to attach is absolutely fundamental to
human development. It sets the template to later developing.
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- "If you think of two babies born on the same day.
One cries a lot and so people don't really want to pick him up a lot. Then
you have the other baby who is one of those cutesy things.
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- "You can see that children create the environment
that they are influenced by. That's where the genetics and the environment
come together. Those two babies actually have different environments, but
that's partly a function of who they are.
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- "You could argue that the genetic component that
makes temperament difficult and hard to cuddle emphasises those elements
of their personality that might later turn out to be difficult or aggressive,"
she said.
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- © BBC MMIV http://news.bbc.co.uk/2/hi/health/3907013.stm
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