They say it takes a village to raise a child — but the village may matter less than we think.

A new Yale study shows that neighborhood factors have a moderate effect on cardiovascular risk and a small impact on obesity and depression for adolescents after they have grown up. The study, published in the journal Health Affairs this September, analyzed data from the National Longitudinal Study of Adolescent to Adult Health (Add Health), a study that followed more than 15,000 adolescents from 1994 to 2009.

“If you take our results at face value, they would suggest neighborhoods have some sort of limited scope,” said study co-author Stephen McLaughlin GRD ’18, who studies public health and epidemiology. “We have to have a little bit of nuance in interpreting our results.”

He explained that it can be difficult to determine if health impacts are caused by an individual’s genetic makeup, their family or their neighborhood, and this study aims to identify how much of a role the latter plays. He also pointed out that the study does not account for complex feedback loops. For instance, clean air in a neighborhood might discourage a family from smoking. Families might also change their behavior based on neighborhood trends.

The effects may seem small, but, according to Tracy Richmond, an assistant professor of pediatrics at Harvard Medical School who researches disparities in adolescent health, its effects might be great across a large population. Her own research has provided evidence that the environment in which a person is raised or attends school affects their health.

“There are so many adult factors that influence cardiovascular risk and depression that I think finding any correlation from where you went to high school is pretty remarkable, especially when you think there are so many complex factors that contribute, including the interaction of genetics and environment,” said Richmond.

According to Andrew Papachristos, a professor of sociology at Yale, “Understanding your zip code can be as important as understanding your genetic code.”

He explained that, just as in genetics, children have no choice about their early environments. They cannot control if their parents live in a house with lead paint or a neighborhood with high crime rates. Despite this, he warned against committing “ecological fallacy,” or assigning to an individual the properties of the whole. Lower-income neighborhoods have higher obesity rates, but there are plenty of people in lower-income neighborhoods who are not obese, he explained.

More than one-third of American adults over the age of 20 are obese.