A study of infants in their first year of life found that infants in families where parents felt their income was insufficient to support the needs of their families were more likely to have delayed brain development. More specifically, on electroencephalography, these children showed a tendency for slower rates of change in alpha peak frequency, alpha power, and beta power. The paper is PNAS.
During the first year of life, your baby’s brain grows faster than at any other time. This period lays the foundation for how a child will think, feel, and interact with others in the future. Most brain cells are already present at birth, but the connections between them increase at an amazing rate.
During the first few months of life, the brain forms millions of new connections every second, helping babies learn from sight, sound, and touch. The brain also begins to insulate (myelinate) nerve pathways, allowing messages to travel more quickly and efficiently.
As babies see faces, hear voices, and experience movement, their sensory systems become more sophisticated. Loving and responsive caregiving plays an important role in shaping the parts of the brain associated with emotions and relationships. Although the areas responsible for planning and self-control are still immature, the foundations of these abilities are beginning to form.
During this period, the brain becomes especially flexible and responsive to experiences. Positive experiences such as talking, cuddling, and playing strengthen healthy brain development, while severe stress and neglect can hinder brain development.
The study’s co-lead authors Helin Zhang and Carol L. Wilkinson, along with colleagues, wanted to identify the psychosocial factors most strongly associated with changes in the early trajectory of brain activity during the first year of life in a group of infants facing high rates of adversity. Because financial strain and psychological stress are often intertwined, the researchers used a new network-based approach to examine how multiple family situations interact, rather than examining each risk factor individually. They drew on data from an ongoing longitudinal study called Baby Steps, which uses electroencephalogram (EEG) recordings of infants’ brain activity.
They analyzed data from 293 infants recruited at a primary care clinic at Boston Children’s Hospital. Although the broader Baby Steps study follows these infants until age 2, the current study focuses on data collected during the first year of life. This sample faced significant economic hardship, with 28% of infants coming from households with monthly incomes of less than $2,100 and 58% from households with monthly incomes of less than $4,400. Demographically, 155 of the infants were boys, 39% were black, and 60% were Hispanic or Latino. English was the primary language in 57% of the infant’s families.
When the infants were 4, 9, and 12 months old, the researchers recorded their brain activity with 5-minute resting-state electroencephalography recordings. The infant’s parents completed a survey, and researchers reviewed the infant’s medical records. In addition to demographic and raw income information, the parent survey also asked an important subjective question: whether parents felt their household income was sufficient to meet their family’s needs.
The survey also collected information on recent stressful life events (Recent Life Events Questionnaire), maternal ratings of stress (Perceived Stress Scale), depressive symptoms (Edinburgh Postnatal Depression Scale), and ratings of neighborhood opportunity levels. Neighborhood assessments assessed educational opportunities, health and environment (such as availability of healthy food and green space), and economic opportunities (poverty and homeownership rates).
Using network-based analysis, the researchers found that income adequacy acts as a central “hub” connecting various stressors. The results showed that mothers who reported that their income was not sufficient to meet their needs were more likely to have lower educational attainment, report lower actual income, experience higher levels of stress, and face more adverse life events.
Controlling for these interrelated variables, income deficits were uniquely associated with delayed brain development in infants. More specifically, young children raised in homes where parents felt that their income was insufficient to support the family’s needs showed slower rates of change in alpha peak frequency, alpha power, and beta power.
Alpha peak frequency is the primary rhythm within the alpha frequency band of brain activity. It typically increases during the first year of life, reflecting maturation of cortical networks and improvement of neural connectivity. Alpha and beta power represent the strength of neural oscillations in their respective frequency ranges.
Developmental increases or rearrangements in these measures are commonly interpreted as markers of increased synaptic growth, myelination, and functional organization of the infant brain. Therefore, slow rates of change in these indicators indicate slow or delayed brain development.
“Taken together, these findings provide a framework for understanding and visualizing how early adversity affects neurodevelopment and provide evidence that maternal income adequacy is potentially useful as an additional screening tool to facilitate the identification of populations most vulnerable and in need of early intervention,” the study authors concluded.
This study significantly contributes to scientific understanding of how multifaceted stress affects infant brain development. However, it should be noted that the observational design of this study does not allow for definitive causal inferences. Although it is very likely that a lack of income leads to delays in infant brain development, it is also possible that other unmeasured factors (such as biological and environmental variables) influence both household income and the pace of infant brain development.
The paper, “Income Lack Impacts Early Brain Development in Young Children Facing Increased Psychosocial Adversity: A Network-Based Approach,” was authored by Haerin Chung, Carol L. Wilkinson, Asher Liu, Alex Job Said, Brianna Francis, Gabriela Cañaveral, Kathleen Conroy, Helen Tager-Flusberg, and Charles A. Nelson.
