"We wanted to know if there is an association between parents' age and common behaviour problems in children. With respect to common behaviour problems, we found no reason for future parents to worry about a harmful effect of having a child at an older age," said Marielle Zondervan-Zwijnenburg, study's lead author.
Researchers analysed the behaviour of 32,892 Dutch children when they were 10 to 12 years old. Problem behaviour was rated by fathers, mothers, teachers, and the children themselves through a series of standardised instruments.
The children, all of whom were born after 1980, were part of four studies--Generation R, the Netherlands Twin Register, the Research on Adolescent Development and Relationships-Young Cohort (RADAR-Y), and the Tracking Adolescents' Individual Lives Survey.
In the Generation R study, mothers' age at child's birth ranged from 16 to 46 and fathers' age at child's birth ranged from 17 to 68. In the Netherlands Twin Register, mothers' age at child's birth ranged from 17 to 47 and fathers' from 18 to 63. In the RADAR-Y study, mothers' age at child's birth ranged from 17 to 48 and fathers' from 20 to 52. And in the Tracking Adolescents' Individual Lives Survey, mothers' age at child's birth ranged from 16 to 44 and fathers' from 18 to 52.
The study found that the children of aged parents had fewer externalizing behaviour problems, as reported by the parents.
The study's authors noted that they focused only on children's externalizing and internalizing behaviour problems, so the findings cannot be generalised to other behaviours.
"It's possible that some of the reason why older parents have children with fewer problems like aggression is that older parents have more resources and higher levels of education," explained Dorret Boomsma, study's co-author.
"But it is important to note that the higher average educational level of older parents does not completely explain the decreased levels of externalizing problems in their children," Boomsma added.