How much you earn 'may affect growth of your child's brain'

The structure and growth of a child's brain may be affected by their parents' income.

In research involving more than a thousand children and young people, scientists in the US found that those with less well-off parents were more likely to have smaller brain surface areas in key regions linked with language and reading. The effects of income and parents' educational history appeared to be independent of genetic factors, researchers from nine US universities said.

Social and economic background has long been linked with variations in brain functioning, but the new study is thought to be the first to suggest these factors can even affect the brain's structure.

A link between income and children's diet, health care, lack of access to good schools and play areas, and even exposure to polluted areas may lie behind the connection, neuroscientists said.

Not all children of poorer families had smaller brain surface areas and the authors of the study said their findings did not mean that a person's social status led to "an immutable trajectory of cognitive brain development".

But the findings are a potent reminder of the long-term impact of health inequalities. Elizabeth Sowell, professor of paediatrics at the University of Southern California, said that the differences in brain structure could be linked to "wider access to resources likely afforded by the more affluent". She said: "Future research may address the question of whether changing a child's environment - for instance, through social policies aimed at reducing family poverty - could change the trajectory of brain development and cognition for the better."

A wide variety of external factors can affect the growth of the brain during childhood and adolescence, when the regions of the brain responsible for the higher cognitive functions such as learning, reasoning and language develop rapidly.

Previous studies have shown that the brains of 10-year-olds who score better on intelligence tests have a greater surface area. During childhood and adolescence, the brain is at its most impressionable - exhibiting what is known by scientists as "experience-dependent plasticity".

The study, published in Nature Neuroscience, recruited 1,099 people between the ages of three and 20. Information on their background was collected through questionnaires sent to parents and detailed pictures of the participants' brains were acquired through high-resolution magnetic resonance imaging (MRI) scans.

A parent's educational background was also linked with their children's brain structure, with additional years at high school or college associated with greater surface area. The effect of parental income on brain structure was most pronounced among the poorest children, said the study's lead author, Kimberley Noble, assistant professor at Columbia University Medical Centre.

"Among children from the lowest-income families, small differences in income were associated with relatively large differences in surface area in a number of regions of the brain associated with skills important for academic success," she said.