Time-varying effects of income on hippocampal volume trajectories in adolescent girls

Abstract

Children from lower-SES families exhibit smaller hippocampal volume than do their higher-SES peers. Few studies, however, have compared hippocampal developmental trajectories as a function of SES. Thus, it is unclear whether initial rank-order stability is preserved, or whether volumes diverge/converge over the course of adolescence. In a sample of 101 girls ages 10–24 years, we examined the longitudinal association between family income and parental education, proxies for SES, and changes in hippocampal volume. Hippocampal volume was obtained using MRI; using mixed modeling, we examined the effects of income and education on hippocampal volume across age. As expected, changes in volume were non-linear across development. Further, trajectories diverged in mid-adolescence, with lower-income girls exhibiting reductions in hippocampal volume. Maximal income-related differences were observed at 18 years, and trajectories converged thereafter. This interaction remained significant when accounting for maternal hippocampal volume, suggesting a unique contribution of environment over potential heritable differences. In contrast, the association between parental education and offspring hippocampal volume appeared to be stable across adolescence, with higher levels of parental education predicting consistently larger hippocampal volume. These findings constitute preliminary evidence that girls from lower-income homes exhibit unique trajectories of hippocampal growth, with differences most evident in late adolescence.

Evidence for a sensitive period in the effects of early life stress on hippocampal volume

“…This research yielded mixed findings concerning the effects of ELS on subsequent HV; whereas some studies demonstrated reduced HV in those with ELS (Hanson, Nacewicz, Sutterer, Cayo, Schaefer, Rudolph, & Davidson, ; Hodel, Hunt, Cowell, Heuvel, Gunnar, Thomas, & Thomas, ), others found no significant association (Frodl, Janowitz, Schmaal, Tozzi, Dobrowolny, Stein, & Grabe, ; Mehta, Golembo, Nosarti, Colvert, Mota, Williams, & Sonuga‐Barke, ; Sheridan, Fox, Zeanah, McLaughlin, & Nelson, ; Tottenham, Hare, Quinn, McCarry, Nurse, Gilhooly, & Casey, ). These mixed findings may be due in part to issues related to measurement, age of assessment (e.g., because the rate of hippocampal growth may be affected by adverse experience (Ellwood‐Lowe, Humphreys, Ordaz, Camacho, Sacchet, & Gotlib, )), and the timing of exposure to stress.…”

The personal data is political

“…As in the case of psychology and genomics, neuroscience research is largely based on data of individuals from WEIRD societies [33], despite a plethora of studies showing that brain development is affected by socioeconomic status, early life stress, or cultural differences [34]- [38]. Indeed, within or across household socio-economic variables during childhood, such as family income, parental education [39], [40] or neighbourhood poverty levels [35], can be traced on trajectories of brain development, and result in differences in brain structure [39] and cognitive functions [41], or gene expression [42]. Differences in brain networks according to socio-economic status are also evident during adolescence [40] and adulthood [36].…”

Cross-sectional and longitudinal associations of family income-to-needs ratio with cortical and subcortical brain volume in adolescent boys and girls

“…In addition to associations with cortical surface area, lower SES in childhood has been related to smaller cortical and subcortical brain volume. More specifically, lower family income has been associated with reduced total gray matter volume (Mackey et al, 2015;McDermott et al, 2019), and higher SES has been associated with larger hippocampal volume in samples spanning childhood to young adulthood (Ellwood-Lowe et al, 2018;Hanson, Chandra, Wolfe, & Pollak, 2011;Hanson et al, 2015;Jednoróg et al, 2012;McDermott et al, 2019;Noble, Houston, Kan, & Sowell, 2012;Yu et al, 2018) and, recently, with larger thalamus and striatum volume (McDermott et al, 2019). Finally, SES has been associated with white matter volume (McDermott et al, 2019;Ursache & Noble, 2016) and with the organization (i.e., the diffusion properties) of white matter tracts.…”

“…Given the central role of the hippocampus in memory, learning, and regulation of responses to environmental stress (Teicher & Samson, 2016), several previous studies of SES and neurodevelopment have examined hippocampal volume using a region-of-interest approach (Ellwood-Lowe et al, 2018;Hanson et al, 2011Hanson et al, , 2015Jednoróg et al, 2012;McDermott et al, 2019;Noble et al, 2012;Yu et al, 2018). In addition, researchers have examined the relation between SES and microstructure of the hippocampal subdivision of the cingulum, which, extending into the temporal lobe, is implicated in memory performance (Bubb, Metzler-Baddeley, & Aggleton, 2018).…”