Early adversity linked to altered hippocampal growth in children

A new study published in Developmental Cognitive Neuroscience sheds light on how early adversity affects brain development in children. Researchers found that greater adversity experienced during the perinatal period (around birth) is linked to smaller hippocampal volume in early childhood but also to faster growth in the right hippocampus throughout childhood. Interestingly, this accelerated growth was associated with an increased risk of depressive symptoms later in childhood.

Previous research has indicated that children exposed to adversity often experience various developmental changes. However, few studies have examined brain development over multiple time points to model the pace of development effectively. The researchers sought to better understand how adversity during the perinatal period impacts the pace of brain development and the potential implications for children’s mental health.

“There are a number of research findings that point to the possibility that children grow up faster in the context of adversity. For example, children exposed to adversity are at increased risk of starting puberty at younger ages and have been shown to have brains that physically look more typical of older peers,” said study author Jonas Miller, an assistant professor at the University of Connecticut and principal investigator of the Biobehavioral Adjustment and Neurodevelopment Lab.

“Few studies, however, have measured the brain at multiple timepoints to effectively model the pace or speed of development. It was also not clear whether adversity that occurs very early in life, such as during pregnancy and the first 6 months after birth, has a lasting relationship with accelerated pace of brain development across childhood, and whether the pace of brain development might have implications for children’s future mental health. We were interested in drawing on data from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study address these questions.”

The study drew data from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study, a comprehensive birth cohort study. Researchers collected neuroimaging data at three time points: 4.5, 6, and 7.5 years of age. They analyzed these scans to measure the volume of different parts of the brain, focusing on the hippocampus.

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The hippocampus is a critical part of the brain located in the temporal lobe. It plays a major role in forming and organizing memories and is also involved in learning and emotional regulation. Shaped like a seahorse, this small, curved structure helps consolidate information from short-term memory to long-term memory.

The sample included 784 children, and the researchers assessed perinatal adversity based on several factors, including birth weight, gestational age, maternal smoking during pregnancy, household income, maternal mental health, and early hospitalization of the child. Each factor contributed to an adversity index, with higher scores indicating greater adversity.

The researchers used magnetic resonance imaging (MRI) to collect high-resolution images of the children’s brains. They then applied advanced techniques to segment and measure the volumes of specific brain regions, particularly the hippocampus. Finally, at age 8.5, the children reported on their depressive symptoms using a standardized questionnaire.

The researchers found that higher levels of perinatal adversity were linked to smaller volumes of the hippocampal body on both sides of the brain at 4.5 years of age. However, these children also exhibited faster growth in the right hippocampal body between ages 4.5 and 7.5. This accelerated growth was associated with higher depressive symptoms reported at age 8.5.

“We were surprised that prenatal and early postnatal risk factors were related to children’s mental health 8.5 years later,” Miller told PsyPost.

The findings suggest that early adversity is biologically embedded in the brain’s development, influencing both the initial size and the growth rate of the hippocampus. Furthermore, the faster growth rate of the right hippocampal body mediated the relationship between early adversity and later depressive symptoms, suggesting that the changes in brain development may underlie the increased risk of depression seen in these children.

“Early life risk factors can accumulate, but so can resources or assets,” Miller explained. “Exposure to multiple adversities during pregnancy and the early postpartum period, such as parental smoking, hospitalization, and parental mental health issues, may predispose children to risky forms of brain development. This might be particularly true when children don’t have access to early life resources and positive conditions, such as breastfeeding, healthy prenatal environments, and parents with positive mental health.”

“We found that when adversities accumulate early in life in the relative absence of resources, children are at increased risk for showing smaller hippocampus at 4 years of age. This region plays a crucial role in memory, emotion, and regulating stress. Despite having smaller hippocampus, these children are also likely to show faster growth in this region across the next three years of childhood, although they don’t appear to catch up with their low-adversity exposed peers.”

“This faster growth of the hippocampus, in turn, is related to children’s increased risk for reporting depressive symptoms,” Miller said. “Taken together, very early life conditions may be embedded in the pace of development of some brain regions, and this may place children at higher or lower risk for experiencing depression in the future.”

While the study provides valuable insights, there are some limitations to consider. For instance, the cumulative adversity score combines various factors, which may not fully capture the complexity of each child’s experiences. Future research could benefit from examining specific types of adversity separately.

“These findings are based on a correlational study design,” Miller noted. “We cannot say that the perinatal adversity, faster pace of brain development, and future depression symptoms are causally related to each other.”

“We want to test whether these findings are specific to the size and growth of the hippocampus, or if they extend to other brain regions, networks, and measures. We are also interested in looking into the potential implications of pace of brain development for children’s plasticity and openness to influence from the environment. We often think of childhood as being a period of increased plasticity. If certain aspects of brain development are accelerated, does that lead to earlier reductions in plasticity?”

“This work would not have been possible without the contributions from my coauthors and the families who participate in the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study,” Miller added.

The study, “Faster pace of hippocampal growth mediates the association between perinatal adversity and childhood depression,” was authored by Jonas G. Miller, Peter D. Gluckman, Marielle V. Fortier, Yap Seng Chong, Michael J. Meaney, Ai Peng Tan, and Ian H. Gotlib.