Researchers find differences in the brains of children from different backgrounds
Norwegian researchers have studied images of the brains of 10,000 American children. They found that parental education and income impact brain development.
Published
Many statistics show a positive impact of high parental income and education levels on children’s development.
On average, these children have better grades in school.
They develop better language skills.
And they enjoy better physical and mental health compared to children with fewer resources.
These differences are well documented in research. But is it possible to find these differences in the brain as well?
Generally quite similar
Norwegian researchers have now put this question to the test. They examined MRI images of the brains of around 10,000 American children aged 9 to 11 years.
Linn Christin Bonaventure Norbom is a postdoctoral fellow at the research centre PROMENTA. She is the lead author of the new study published in JCPP Advances.
She says that, in general, the brains of children with high and low socioeconomic status are very similar.
"We therefore need a very large dataset to be able to determine if there is a clear effect," she says.
The research group that Norbom is a part of at the University of Oslo studies brain development and its connection to mental health problems. The researchers are also interested in finding out why there are such large social differences in these disorders.
Significant changes in childhood
Our brain changes a lot during childhood.
For one, the region of the cerebral cortex expands. This happens very quickly at first, then more gradually.
"What lies beneath the cerebral cortex grows and pushes it outward so that it becomes much larger until it stabilises and becomes a mature brain," the researcher says.
The expansion of the cerebral cortex area is therefore a natural – and positive – part of the maturation process.
Different sizes of the cerebral cortex
In studying American children's brains, the researchers found clear differences in the cerebral cortices of children who come from different socioeconomic backgrounds.
Children whose parents have spent many years in school and have a high annual income have a larger surface area of the cerebral cortex than children whose parents have few such resources.
The researchers also found that the frontal parts of the cerebral cortex are larger in children from a high socioeconomic background. These areas are crucial for regulating thoughts and emotions, and are important for good mental health.
Children from families with lower socioeconomic status also showed more symptoms of mental health problems.
Conflicting findings
The researchers also found large differences when they use another, less common measure for brain development.
But those results point in a slightly different direction.
Children with parents of low income and lower education appear to have more myelin in the cerebral cortex than children from wealthier families.
Myelin is a fatty substance located beneath the cerebral cortex. It helps the nerves to efficiently send signals to each other, which is very important for brain function.
“This appears to be a finding that conflicts with what we found when we studied the cerebral cortex's surface area,” says Norbom.
A paradox?
The researchers have discussed this apparent paradox in detail.
“The results could be related to the method we used. But we also have a theory as to why children from low socioeconomic status homes actually seem to have a more mature brain in this area,” says the researcher.
“A well-known theory in developmental psychology is that if you experience a lot of stress as a child, you’re forced to develop faster. The body feels a pressure that makes you mature faster. Other research has, for example, shown that children who live under such stress reach puberty sooner."
This might be the reason why these children seem to have more myelin than other children, Norbom notes.
Underlying factors
The researcher believes it is important to remember that income and education indirectly influence many factors that have a more direct impact on brain development.
The study does not have data that can explain the reason for the differences they have found.
But the researchers asked themselves whether the differences have to do with various factors – such as diet, environmental pollution, unsafe neighbourhoods or stress.
Or are children more stimulated when parents have a higher level of education and therefore more adept at reasoning and solving tasks, for example?
Norway also has big differences
Fartein Ask Torvik is a senior researcher at the Norwegian Institute of Public Health (NIPH), where he works on social inequity in mental health.
Torvik has read the study and finds it interesting and believes it is also relevant for conditions in Norway.
“The social difference in mental health problems is very strong, also in Norway. Those with lower education and income have a much higher risk of mental health problems," he says.
This applies not just to adults, but to their children as well.
In a 2021 study from NIPH, Torvik and other researchers found that children of parents with the very lowest income have a three to four times as high a risk of being diagnosed with mental health problems as children of the wealthiest families.
Interesting to find the cause
“We know that these differences exist, so it’s very interesting to find out where they come from. We know that mental health problems are related to brain structure. Everything we think and feel happens in the brain,” Torvik says.
He notes that it is important to be aware that what the researchers found in the new study are average differences in a large group of children.
“You can’t use MRI scans to diagnose individuals,” he says.
Studied adopted children
Torvik believes there are two possible main explanations for the differences found in the brains of the children
One is that children share genes with their parents. Mental health problems can therefore be inherited.
The second possibility is that something in the environment the child grows up in has an effect.
“We have other studies that suggest growing up in families with low socioeconomic status has an independent effect on mental health,” he says.
Distinguishing between genetics and environmental factors can be challenging.
This is what researchers at NIPH tried to address in the 2021 study, says Torvik.
In part of the study, they looked at adopted children, meaning families where children and parents were not genetically related to each other. They found a greater proportion of mental health problems among those living in low-income families compared to those in high-income families.
Greater inequality in the United States
Norbom and her colleagues have studied the brains of American children. Their data comes from the Adolescent Brain Cognitive Development (ABCD Study) in the USA. This is a unique collection of MRI images of children's brains and contains images of brains from many different social strata across the United States.
“We have no comparable database in Scandinavia, so it isn’t possible to say that these findings are transferable to Norwegian children,” Norbom explains.
She points out that the differences between people in the USA are much greater than in Norway.
American children have completely different everyday lives and education systems than children in Norway.
Belief in transferability
However, Torvik believes there is significant transferability from this American study to the Norwegian population.
“I think we’d have a lot of similar findings. We have quite significant disparities here in Norway as well,” he says.
When the researchers compare the very poorest with the very richest in the population, they find exactly the same difference in life expectancy among Norwegians and Americans.
“The difference is a whole 14 years among men, both in Norway and the USA," he says.
A sensitive research field
Norbom and other neuroscientists have not previously focused much on the social environment in their research, nor on people's education and income, which are often important to study in the social sciences.
“At PROMENTA, our work is interdisciplinary, so we’re interested in how both genetics and environment influence development and mental health,” she says.
She admits that this is a sensitive topic to research.
It could be perceived as though what is in the brain cannot be changed. But that is not the case, Nordbom believes.
“We can do more with our brains than with our genes, for example,” she says.
As a society, it could therefore be important to avoid large socioeconomic disparities to promote children’s healthy development and mental health, she believes.
“This is something we know from several different fields of study. It's now supported by neuroscience research as well,” says Norbom.
Reference:
Norbom et al. Parental education and income are linked to offspring cortical brain structure and psychopathology at 9–11 years, JCPP Advances, 2024. DOI: 10.1002/jcv2.12220
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Translated by Ingrid P. Nuse
Read the Norwegian version of this article at forskning.no
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