The trajectory of cortical gray matter development in childhood is characterized by increase in volume resulting from early neurogenesis, peaking at puberty and subsequently losing volume and thinning by selective elimination and myelination. Although this inverted U-shaped trajectory, as well as cortical thickness has been associated with cognitive and emotional function there is no current data to relate this to childhood depression unlike in adult patients where decreased cortical gray matter has been shown to be associated with depression.
In a study published in JAMA Psychiatry researchers from Department of Psychiatry at Washington University School of Medicine in St. Louis, MO report on a longitudinal neuroimaging and behavioral study of 193 children aged 3 to 6 years from September 2003 to December 2014 using 3.0 T MRI scans and psychiatric interviews to explore the relationship between the trajectory of gray matter development and depression.
Of the 193 children, 90 had a diagnosis of major depressive disorder; 116 children had 3 full waves of neuroimaging scans. Findings demonstrated marked alterations in cortical gray matter volume loss (slope estimate, −0.93 cm3; 95% CI, −1.75 to −0.10 cm3 per scan wave) and thinning (slope estimate, −0.0044 mm; 95% CI, −0.0077 to −0.0012 mm per scan wave) associated with experiencing an episode of major depressive disorder before the first magnetic resonance imaging scan.
According to the authors children with depression symptom scores 2 SDs above the mean had reduction in volumes of gray matter at almost twice the rate of those with no childhood depression symptoms.
Interestingly there was no significant relationship between family history of depression, a marker of genetic risk or experiences of traumatic or stressful life events during this period and gray matter development. This led the authors to speculate that changes in cortical gray matter related to childhood depression may reflect experience-dependent neuroplasticity.
In an accompanying editorial, Gotlib & Ordaz (2015) highlights the multiple ways by which longitudinal neuroimaging research can be useful in the understanding of psychiatric disorders, (1) by revealing variability in etiologic pathways to disorder, by elucidating how external influences can alter neural trajectories and by clarifying critical changes during specific sensitive developmental periods.
Determining the optimal time to intervene could influence long lasting changes in the trajectories of brain development.