In the first year of life, human babies are wrinkled, fragile, and vulnerable to all kinds of stressors at home and in the world: chaotic sleep schedules, over-stimulation, parental stress. When the adversity is chronic, it can have a lasting impact on how their brains develop.
But adversity is a complicated web, with many intersecting threads: Parental stress often overlaps with other stressors, such as financial shortfalls, big life disruptions, as well as disadvantages in neighborhood, housing, and education. Scientists have wanted to understand whether the impacts of some of these factors can be isolated, and which ones matter most to the babies’ long-term brain health.
Recently, a team of Boston Children’s Hospital researchers decided to sort through data from an ongoing project called Baby Steps, which is part of a program serving mostly low-income families at Boston Children’s Hospital. They studied nearly 300 babies who came to the hospital for regular visits at 4, 9, and 12 months. During the visits, the researchers recorded resting-state EEGs in the babies and surveyed the parents (typically moms) about their income levels, their perceptions about whether their incomes met their needs, caregiver stress, challenging life experiences, and the kinds of opportunities available in their neighborhoods.
Rather than try to isolate individual variables, the scientists used a network approach to map connections between them. Next, they looked for clusters, to identify which factors were most central in the network. They found that a single variable acted as the primary bridge between family stress and infant brain development. The culprit was income sufficiency—not the actual dollar value of family income but whether the caregiver felt that income was enough to cover family and household costs. They published their results in Proceedings of the National Academy of Sciences.
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“Children grow up in complex, dynamic environments where stressors are interconnected,” said Haerin Chung, co-author of the study, in a statement. “By using a network approach, we can identify which factors are most central—much like identifying influential nodes in a social network. Changing those central factors may have ripple effects across a child’s developmental environment.”
Moms who said their incomes were never enough also tended to have lower levels of income and education, more stressful life events, and higher overall stress. But even after the scientists accounted for these other factors, income insufficiency still showed a unique association to how well babies’ brains developed.
The scientists focused most closely on brain features that typically develop quickly in the first year of life, and show up on EEGs in alpha and beta ranges, linked in other research to later cognitive development in areas such as executive function, language, and attention. Babies whose moms said their incomes were rarely or never sufficient generally showed slower increases in alpha power, slower increases in alpha peak frequency—a classic marker of maturation in infancy—and consistently lower beta power. These differences were noticeable when the babies reached around 9 months of age.
Some previous studies have shown that adversity can accelerate certain aspects of brain development in babies. But the scientists point out that different populations may show different responses. The population sample examined in the clinic had more severe and concentrated adversity than most general population studies, they note. Also, it’s possible that brain development could catch up later in life. The scientists plan to re-check EEG patterns after 24 months to see how the existing patterns shape up.
The scientists say their findings could be useful in the clinic. Asking new parents whether their incomes are sufficient to cover their needs could work as a quick screen for developmental vulnerability in their babies—not as a replacement for full assessment, but just as an early warning light. 
Lead image: Jump.Studio / Shutterstock
