According to the preprint study, changes in brain development linked to early adversity differ based on age and experience. For example, while poverty is associated with decreased brain volume in certain regions during childhood, these regions begin to have more average volumes as we age. Conversely, early interpersonal adversity (such as maltreatment) is associated with initially greater volumes in some brain regions that reduce as we age. The authors write:
“Findings demonstrate that early-life adversity does not have an ontogenetically uniform impact on brain volumes, but instead exhibits age-, experience-, and region-specific associations. Relative to non-exposed comparisons, interpersonal early adversity (e.g., family-based maltreatment) was associated with initially larger volumes in frontolimbic regions until ~10 years old, after which these exposures were linked to increasingly smaller volumes. By contrast, socioeconomic disadvantage (e.g., poverty) was associated with smaller volumes in temporal-limbic regions in childhood, which were attenuated at older ages.”
The current work examines the link between early life adversity, age, and brain volume. To accomplish this goal, the authors conducted a literature search and identified 92 unique samples from 81 articles with 27,234 participants for inclusion in the meta-analysis. The authors used four inclusion criteria in their search for studies to help them better understand the relationship of early adversity to brain volume:
- Participants aged 18 years and younger.
- A measure of early adversity before the age of 18
- An MRI measurement of brain volume
- Sufficient amount of data to calculate effect size
The authors and their research assistants then coded each of the included articles for early interpersonal adversity (caregiving disruptions, caregiver psychopathology, maltreatment, and interpersonal trauma) and socioeconomic disadvantage (indicators of low family socioeconomic status, non-interpersonal trauma, community crime/violence exposure, neighborhood poverty, and area deprivation). 65% of the included samples (60) involved early interpersonal adversity versus 35% (32) for early socioeconomic disadvantage.
Early interpersonal adversity was associated with a larger amygdala, hippocampus, ventral anterior cingulate cortex, ventromedial prefrontal cortex, and ventrolateral prefrontal cortex until age 12. After age 12, interpersonal adversity was associated with reduced volume in the same regions.
Early socioeconomic disadvantage was associated with a smaller amygdala, hippocampus, parahippocampus, and temporal gyri until the age of 12. However, these differences disappear as participants approach middle and late adolescence.
The authors acknowledge several limitations to the current study. First, the methods used to collect data on adversity in the included articles could not account for possible important factors such as the timing of adversity exposure.
Second, there was not much data for infants and toddlers, likely due to the complications of collecting MRI data from that population.
Third, the data for brain volume were collected cross-sectionally, meaning it came from different participants. A clearer picture of the connection between early adversity and brain volume would likely result if MRI data were collected from the same participant at different ages longitudinally.
Fourth, while articles included in the meta-analysis focused on one type of adversity, it is possible the participants could have been exposed to other types. Finally, 70% of the included samples were from North America, vastly limiting generalizability to other populations.
The authors conclude:
“Findings from this meta-analysis underscore that the careful consideration of development facilitates a deeper appreciation of how the developing brain adapts to specific experience types.”
Recent research has found that poverty leads to a reduced cortical surface area, which is associated with neurological and behavioral problems in adolescents. Children living in poverty show brain physiology similar to adults with frontal lobe damage. Childhood poverty has also been linked to early neurological impairment and smaller brain sizes, whereas financial resources have been found to increase infant brain activity. Authors have also noted that neglect and abuse change children’s brains.
Critics of brain imaging studies have noted that they are likely false due to inflated effect sizes and called such studies “problematic if not unsubstantiated.” One analysis found that MRI studies were unreliable and not suitable for research. At least two studies have found that there are no meaningful brain differences in depressed versus non-depressed populations. Another piece of research found that brain scans cannot differentiate between mental health conditions.
Vannucci, A., Fields, A., Hansen, E., Katz, A., Kerwin, J., Tachida, A., Martin, N., & Tottenham, N. (2023). Interpersonal early adversity demonstrates dissimilarity from early socioeconomic disadvantage in the course of Human Brain Development: A meta-analysis. https://doi.org/10.1101/2023.02.16.528877 (Link)