A simple test at the age of three can determine whether children will grow up to be a burden on society, needing excessive welfare, spending time in prison or becoming obese, a 35-year study has shown.
Scientists at King's College London followed more than 1,000 children from before school until they were 38, to find out if it was possible to predict who would go on to lead troubled lives.
All were given a 45-minute test aged three to gauge intelligence, language and motor skills, and were assessed for their levels of tolerance, restlessness, impulsiveness and social disadvantage.
After 35 years, the researchers found one fifth of the group was responsible for 81 per cent of the group's overall criminal convictions, three quarters of its drug prescriptions, two thirds of welfare benefit payments and more than half of nights in hospital.
But crucially, they discovered that the outcomes could have been predicted decades earlier, simply by looking at which children attained the lowest test scores aged three.
The team believe that if all children could be tested it would be possible to work out which were at greatest risk, so that interventions could be made to prevent them slipping into a life where they were a burden on the state.
"About 20 per cent of the population is using the lion's share of a wide array of public services," said Prof Terrie Moffitt, of King's College and Duke University in North Carolina.
"The same people use most of the (health system), the criminal courts, insurance claims for disabling injury, pharmaceutical prescriptions and special welfare benefits. We also... found that 20 per cent begin their lives with mild problems with brain function and brain health when they were very small children. Looking at health examinations really changed the whole picture."
Prof Moffitt added: "Being able to predict which children will struggle is an opportunity to intervene in their lives very early to attempt to change their trajectories for everyone's benefit and could bring big returns on investment for government."
The team began the project to test the "Pareto principle" - also known as the "80-20 rule" - which states that in the majority of systems, around 80 per cent of the effects come from about 20 per cent of the causes.
This principle has been found to work in computer science, biology, physics, economics and many other fields. The research found that the rule was also true for societal burden.
As well as increased criminality and NHS use, the most costly participants of the study also carried 40 per cent of the obese weight.
"Most expenses from social problems are concentrated in a small segment of the population," said co-author Prof Avshalom Caspi, of King's College and Duke University.
"So whatever segment of the health, social or judicial system that you look at, we find a concentration. That concentration approximates what Pareto anticipated over 100 years ago.
"And we can predict this quite well, beginning at age three by assessing a child's history of disadvantage, and particularly their brain health. There is a really powerful connection from children's early beginnings to where they end up."
Rena Subotnik, director of the Center for Psychology in Schools and Education for the American Psychological Association, said that if problem children could be targeted early, society could benefit hugely in the long term.
"You get the best bang for the buck with early intervention," she said.
The study was published in the journal Nature Human Behaviour.
The Daily Telegraph, London
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