A child’s family income and the neighbourhood they grow up in may have a stronger influence on brain development than factors such as IQ, parenting style or health history, according to new research.
The study, led by researchers at Washington University School of Medicine in St. Louis, Mo., analyzed brain scans from nearly 12,000 children aged nine and 10.
The researchers examined 649 factors that can shape a child’s life, including sleep, screen time, physical and mental health, friendships, family relationships and socioeconomic conditions.
They found that socioeconomic factors, like family income, homeownership, neighbourhood poverty rates and access to resources, had the strongest connection to children’s brain structure and function.
According to the study, socioeconomic factors accounted for about 16 per cent of the variation seen in measures of brain function, a larger share than any other category examined.
The researchers used MRI scans from children participating in the U.S.-based Adolescent Brain Cognitive Development (ABCD) Study, a long-term project tracking child health and brain development.
They grouped the 649 variables into 12 broad categories, including socioeconomic conditions, screen time, cognitive abilities, physical health, mental health, parenting, personality and medical history.
Among the 40 factors most strongly linked to brain function, 37 were related to socioeconomic conditions. Of the top 40 factors associated with brain structure, 35 were socioeconomic.
Sleep, stress and screen time were also among the factors linked to brain development, though not as strongly as socioeconomic conditions.
The researchers found that socioeconomic factors were most closely associated with areas of the brain involved in movement and sensory processing. Those same regions are known to be sensitive to sleep quality and stress.
Nico Dosenbach, a professor of neurology at Washington University and co-author of the study, shared some of his insights on the study in an interview with CTVNews.ca.
“The lower order primary regions of the brain, primary motor, primary sensory cortex are the most affected by basic physiological variables like arousal, sleep, and stress,” Dosenbach said in a Zoom interview on Thursday. “So, if you have someone that’s sleep deprived, those are the brain regions that you can see a change in the brain functioning.
“If you give someone a stimulant drug like caffeine or Adderall, Ritalin, those are the same brain regions where you see an effect in the opposite direction,” he added.
The findings suggest that children having a socioeconomic disadvantage may affect their brains indirectly through factors such as chronic stress and disrupted sleep, the authors said.
The study also found no evidence that the relationship between socioeconomic factors and brain development was driven by demographic characteristics, such as race or sex.
The researchers further examined long-standing claims that intelligence can be identified through physical features of the brain.
After accounting for socioeconomic conditions, many of the previously observed links between IQ scores and brain structure or function became much weaker. According to researchers, roughly 70 per cent of those associations were no longer statistically significant.
In a separate analysis that looked only at children from high socioeconomic backgrounds, researchers found no correlation between IQ scores and measures of brain structure or function.
“If you take only kids that are middle class to upper, you can no longer predict their IQ from their brain data, zero effect,” Dosenbach said. “The link to the biology vanishes completely.”
The authors said the findings suggest that differences in children’s daily environments may play a larger role in shaping brain development than previously understood.
