Abstract
Socio‐economic disadvantage increases exposure to life stressors. Animal research suggests early life stressors impact later neurodevelopment, including myelin developmental growth. To determine how early life disadvantage may affect myelin growth in adolescence and young adulthood, we analysed data from an accelerated longitudinal neuroimaging study measuring magnetisation transfer (MT), a myelin‐sensitive marker, in 288 participants (149 female) between 14 and 25 years of age at baseline. We found that early life economic disadvantage before age 12, measured by a neighbourhood poverty index, was associated with slower myelin growth. This association was observed for magnetization transfer in cortical, subcortical and core white matter regions, and also in key subcortical nuclei. Participant IQ at baseline, alcohol use, body mass index, parental occupation and self‐reported parenting quality did not account for these effects, but parental education did so partially. Specifically, positive parenting moderated the effect of socio‐economic disadvantage in a protective manner. Thus, early socioeconomic disadvantage appears to alter myelin growth across adolescence. This finding has potential translational implications, including clarifying whether reducing socio‐economic disadvantage during childhood, and increasing parental education and positive parenting, promote normal trajectories of brain development in economically disadvantaged contexts.
Highlights
Socio-economic disadvantage (SED) is associated with increased exposure to childhood adversity (Pascoe et al, 2016), and is associated with problematic physical and mental health and poorer educational and employment outcomes (Evans & Cassells, 2014; Johnson, Riis, & Noble, 2016; McDermott et al, 2019)
We avail of a unique longitudinal sample of young people and in vivo quantitative magnetic resonance imaging (MRI) that provides a measure of macromolecular content sensitive to myelin, to examine the effects of SED on myelin development
We recently mapped neurotypical myelin development during adolescence and young adulthood, using myelin-sensitive magnetization transfer saturation (MT) (see (Turati et al, 2015) and we showed that myelin growth is tied to aspects of mental health (Ziegler et al, 2019)
Summary
Socio-economic disadvantage (SED) is associated with increased exposure to childhood adversity (Pascoe et al, 2016), and is associated with problematic physical and mental health and poorer educational and employment outcomes (Evans & Cassells, 2014; Johnson, Riis, & Noble, 2016; McDermott et al, 2019). Animal studies, where early stressors are under experimental control, show a causal impact of adversity on brain growth (Howell et al, 2013; Liu et al, 2012; Zhang, 2017). They cannot be generalised directly to human populations, animal studies are critical for pinpointing the consequences of risk exposure to processes such as myelination, which are measurable in humans. Microstructural measures are mechanistically important, as cortical myelin likely reflects local neuritic insulation and fibre density (Glasser, Goyal, Preuss, Raichle, & Van Essen, 2014). Understanding mechanisms can improve conclusions about causality (Broadbent, 2011), and weaknesses in causal claims (Wax, 2017) can be bolstered by studying critical markers of brain development in relation to SED exposure (Donahue, Glasser, Preuss, Rilling, & Van Essen, 2018)
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