MRI scans of nearly 12,000 children have revealed that socioeconomic factors account for at least 16% of the variability in measures of children's brain function -- far more than IQ, parenting style, or health history, researchers have found.
However, a team led by Nico Dosenbach, MD, PhD, of Washington University in St. Louis, also reported that neighborhood poverty, family income, and chronic stress leave measurable imprints on the brain's structure and function. The study results were published June 11 in Science.
"We set out to compare hundreds of influences on the developing brain on a level playing field, and for the first time at this scale, we showed that socioeconomic conditions leave the deepest imprint of any factor we looked at,” Dosenbach said in a statement released by the university.
Resting-state functional connectivity and cortical thickness are among the most widely used neuroimaging measures of human brain function and structure, according to the researchers, who noted that "cortical thickness has been reliably linked with development, aging, socioeconomic status, and mental health." Previous studies have typically assessed intelligence quotient or "total psychopathology," but have not necessarily evaluated whether there is a connection between brain function/structure and a person's environment.
To address this gap, Dosenbach and colleagues analyzed brain scans from 11,878 children between nine and 10 who are participating in the NIH-funded Adolescent Brain Cognitive Development Study. Their goal was to assess how a child’s environment, health and regular activities are related to brain development via 649 variables divided into 12 categories:
- Cognitive abilities, such as test scores and memory,
- Culture and environment, such as religion, language, and exposure to noise or pollution,
- Demographics, including race and sex,
- Medical history,
- Mental health,
- Parenting,
- Personality, including factors such as extraversion and self-control,
- Physical health,
- Screen time,
- Social adjustment, such as friendships and bullying,
- Socioeconomics, and
- Substance use, including use of or exposure to people using illicit drugs and alcohol.
The investigators performed analyses to assess the links between each variable and both brain structure (measured by the thickness of the cortex) and function (indicated by the strength of connections between key functional networks in the brain).
Of the top 40 variables linked to brain function, 37 were socioeconomic, and of the top 40 tied to structure, 35 were socioeconomic, the group reported. These variables included the social and economic resources in the child's neighborhood, and were strongly influenced by family income, homeownership and poverty rates, and access to transportation. The team noted that the remaining top variables were related to sleep, screen time, and stress.
One key finding of the study was that socioeconomic variables were strongly associated with functional features in the motor and sensory areas of the brain, which are highly sensitive to day-to-day variation in sleep and stress, the authors explained, writing that "what might look like a brain difference in cognitive ability is more likely a reflection of differences in everyday burdens such as fatigue and chronic stress than a difference in intellectual capacity."
"The brain of a child from a low socioeconomic background looks like that of a child from a high socioeconomic environment that has been sleep-deprived and stressed," Dosenbach said. "It's not a less-smart brain, … [but] a tired and stressed brain. The good thing is that sleep and stress are both modifiable. If we can find a way to improve sleep and reduce stress for children from households with more limited socioeconomic opportunities, we may be able to reduce brain differences linked to socioeconomics."
Access the full study here.
