Children living in disadvantaged neighborhoods are more likely to become obese and have mental disorders than those growing up in more advantageous areas. This effect seems to depend more on the environment and not so much on a child’s genetic risk, a study suggests.
The reasons for this effect are not clear, but the data suggest that policies and programs that affect neighborhoods may have a greater impact in preventing obesity in children.
However, these results should not be over-interpreted, and policies should take into consideration both the social and physical environment plus an individual’s characteristics.
The findings appeared in the study, “Genetics and the geography of health, behaviour and attainment,” published in the journal Nature Human Behaviour.
Earlier studies provide evidence that children growing up in disadvantaged neighborhoods exhibit worse physical and mental health and have poorer educational and economic outcomes compared with children raised in more advantageous neighborhoods.
But how much of this influence is actually due to environment and what comes from genetic “selection effects” — the tendency of certain families with a given genetic background to live in certain neighborhoods — is unclear.
Dissociating one from another and determining each’s weight is important in determining the focus of policies and interventions to improve children’s health and reduce inequalities.
With this in mind, a team led by researchers at New York’s Columbia University Mailman School of Public Health and the University of California at Irvine considered the question of whether a child’s neighborhood influences his or her health and life chances. Specifically, they were interested in understanding the part played by the neighborhood itself versus the individual’s genetic risk — the long-debated question of whether environment or genes matters more.
They crossed neighborhood data with genetic, health, and social outcome data for more than 7,000 young people of European descent in the U.K. and U.S. who had taken part in the British E-Risk and American Add Health studies.
E-Risk – the Environmental Risk Longitudinal Twin Study — has followed 2,232 twins born in England and Wales into young adulthood, and Add Health — The National Longitudinal Study of Adolescent to Adult Health — has followed 15,000 American high school students into adulthood.
Researchers tested whether worse-off neighborhoods had a higher concentration of people at genetic risk for health and social problems including obesity, schizophrenia, teen pregnancy, and poor educational outcomes.
But the findings were unexpected. Researchers were surprised to see that the fact that children in worse neighborhoods were more frequently affected by obesity or mental problems did not depend so much on having a higher genetic risk.
“Surprisingly, for obesity, one of the most prevalent and costly health problems facing this generation, we found no link between neighborhood and genetic risk,” Candice Odgers, PhD, professor of psychological science at the University of California, Irvine and senior author of the study, said in a press release. “Children who grew up in worse-off neighborhoods were more likely to become obese by age 18, but they did not carry a higher genetic risk for obesity than their peers living in more advantaged neighborhoods.”
The results were similar for mental health issues. There was little evidence that having a higher genetic predisposition was why children in worse-off neighborhoods experienced mental disorders more often.
By contrast, there was a modest but observable link between genetic risk and a greater tendency toward poorer education and teen pregnancy in young people living in disadvantaged areas.
But genetic risk alone accounted for just a fraction of these differences.
The extent of genetic risk between the highest-risk and lowest-risk neighborhoods “could account for, at most, only about 15% of the observed differences in poor educational qualifications and about 10% of the observed differences in NEET [Not in Education, Employment, or Training] status between these neighborhoods,” the researchers said.
Researchers say this finding provides some reason for hope that interventions targeted at neighborhoods — especially for physical health (e.g. obesity) and mental health — will have a significant impact on improving children’s health and their chances in life.
Despite that, policymakers should not over-interpret neighborhood effects, researchers advised.
“This finding suggests that we should consider neighborhoods when interpreting the results of studies searching for genes related to these outcomes, and also that we should consider genes when examining the effects of neighborhoods,” said study leader Daniel Belsky, PhD, professor of epidemiology at the Columbia Mailman School.
“For example, people observed to live in a friendly suburb, remote ranch, quaint village, and luxury high-rise are not found in those neighborhoods randomly by accident; people end up in such locations selectively. But regardless of the location, they all respond to incentives and opportunities,” the team stated.
Therefore, more precise assessments “of selection processes that influence where people live can help to inform policies and programs to craft incentives and opportunities that promote healthy development for everyone,” they concluded.