Last Updated: 2003-08-29 8:11:11 -0400 (Reuters Health)

LONDON (Reuters) - The youngest children in any school year face more stress than their older peers and are at greater risk of developing mental illness, scientists have found.

A survey of more than 10,000 children in Britain between the ages of 5 and 15 showed that regardless of when their school year began, if they were the youngest in the class they faced greater stress.

"It is not a huge stress like family problems, trauma or being in an accident. But it is a moderate stress and, given that it applies to a lot of kids, it is a serious health threat," study leader Robert Goodman told Reuters.

Goodman and his team at the Department of Child and Adolescent Psychiatry at King's College London said the study stripped away seasonal factors that can cause stress, clearly exposing the school year effect.

In England and Wales the oldest children in the school year are born in September, with the youngest in August - the middle of the northern hemisphere summer.

By contrast in Scotland the oldest are born in March and the youngest in February - the start of spring.

But there were no differences in the findings between the different school years.

"They are sufficiently far apart to strip away any seasonal effects, so we have been able to rule that out," Goodman said.

The study, reported in the British Medical Journal, involved questions to children, parents and teachers covering all aspects from their emotions to social behavior and peer relations.

It found a greater incidence of mental health problems among the school year youngsters than among their older colleagues.

"We found that this was true all the way through the age range in our study," Goodman said. "Other studies have also found that the younger in the school class tend to have lower levels of university entrance."

He said the study showed the need for greater flexibility among schools and policy makers on cut-off dates for school year entry - perhaps allowing an extra year of pre-school for a child who would otherwise be the class fledgling.