A study has shown that babies who weigh less than 1kg at birth are more likely to grow up with behavioural problems.

The research was conducted in four countries - Holland, Canada, the US and Germany - to see if cultural differences altered the outcome for low birth weight babies.

Researchers studied more than 400 low birthweight children aged eight to ten, whose parents completed the child behaviour checklist and compared them to normal birth weight children.

Behavioural problems seen in low birthweight children were similar in the four countries, suggesting neurological causes rather than cultural differences in the way they were raised.

Doctors now believe there could be damage to the nervous system in low birthweight babies that lead to attention deficit and hyperactivity problems, says a report in this week's edition of medical journal, The Lancet.

But they also suggested that the social difficulties in children who were born preterm could be down to differences in the relationship they have with parents who face extra difficulties in coping with a preterm child who have been facing life-threatening complications after birth.