WEDNESDAY, April 20 (HealthDay News) -- Persistent poverty harms the cognitive development of children, but family instability has no effect, a new study suggests.

Researchers analyzed data collected from almost 19,000 British children and their families when the children were 9 months, 3 years and 5 years old. The data provided insight into family poverty, family transitions, family demographics and housing conditions.

Most of the families (62.1 percent) were not poor at any of the three assessment points, but 13 percent did experience persistent poverty. Most parents (56.6 percent) were in a stable marriage, 12.7 percent were continuously cohabitating with the same partner, and 7.8 percent were continuously single.

The study found that children in stable two-parent families showed higher cognitive abilities than those in one-parent families or those who experienced a change in living arrangements.

They also found that children growing up in persistent poverty scored lower on cognitive tests than those who had never experienced poverty.

After they accounted for a number of factors, the researchers concluded there was no link between family structure/instability and a child's cognitive ability, but persistent poverty did have a strong and significant negative effect on a child's cognitive functioning at 5 years of age.

The study appeared online April 20 in the Journal of Epidemiology and Community Health. The researchers were from the Institute of Education at the University of London and the Institute of Psychiatry at Kings College London.

More information

The Nemours Foundation has more about child growth and development.