Over-active children who cannot concentrate and act impulsively as early as 3 years old tend to become troubled adults unless they learn self-control along the way, a study says.

An international team of researchers examined young children in New Zealand and Britain and found that low-scorers on measures of self-control faced more financial, health and substance-abuse problems as they grew up.

Measures of low self-control in the study of 1,000 New Zealand children included "low frustration tolerance, lack of persistence in reaching goals, difficulty sticking with a task", says the study in the Proceedings of the National Academy of Sciences.

Other indicators were "over-active, acts before thinking, has difficulty waiting turn, restless, not conscientious".

The children who scored lowest on those counts faced a host of problems as adults, such as "breathing problems, gum disease, sexually transmitted disease, inflammation, overweight, and high cholesterol and blood pressure", the study says.

Researchers also saw those children emerge as adults with financial woes, such as credit-card debt.

"They were also more likely to be single parents, have a criminal conviction record, and be dependent on alcohol, tobacco, cannabis and harder drugs," the study says.

"These adult outcomes were predictable across the entire spectrum of self-control scores, from low to high," says Duke University psychologist Terrie Moffitt, lead researcher on the study.

The same researchers also looked at a study of 500 pairs of fraternal twins in Britain and tracked the differences between the lower self-control twin and the higher self-control twin as they aged.

"The sibling with lower self-control scores at age 5 was more likely than his or her sibling to begin smoking, perform poorly in school and engage in antisocial behaviors at age 12," the study says.

Co-author, Avshalom Caspi of Duke University, says the findings suggest that an individual's ability to exert self-control has an influence of its own and is independent from the environment in which one is raised.

"This shows that self-control is important by itself, apart from all other factors that siblings share, such as their parents and home life," Caspi says.

The researchers say they found evidence those children who changed their ways and learn to exert more self-control fared better in adulthood than their counterparts, indicating that behavior changes can show positive results.

"The good news is that self-control can change. People can change," says Alexis Piquero, a professor of criminology at Florida State University who was not a part of the study.

Agence France Presse