Individual Differences in Developmental Trajectories of Global and Subcortical Brain Volumes Between Late Childhood and Late Adolescence: Findings From a 12‐Wave Neuroimaging Study

Adolescence is characterised by protracted structural brain development, with different brain regions showing distinct developmental trajectories. While studies have identified average developmental trajectories, few have formally quantified individual differences in the developmental trajectories of global brain structures and subcortical regions across adolescence. Utilising the unique 12 waves of high temporal resolution MRI data from the Danish HUBU cohort (N = 90; ages seven to 21; 745 scans; on average 8.30 scans per participant) and nonlinear mixed modelling techniques, we examined both group and individual-level patterns of volumetric change in global brain measures and subcortical regions. At the group level, cortical grey matter, total brain, caudate, putamen, accumbens, and thalamus volume decreased, while white matter, amygdala, hippocampus, and pallidum volume increased. We observed substantial interindividual variability in the rate of volumetric change in the caudate, as well as in the age at which cortical grey matter, white matter, and pallidum volumes changed most rapidly. For instance, the age of most rapid cortical volumetric decline varied by up to 7.5 years among individuals. Maturational trajectories also differed by sex. Our findings quantify overall trajectories, as well as individual and sex differences in volumetric development in subcortical and global brain volumes. Future research can build upon these findings to investigate the extrinsic and intrinsic factors that influence interindividual variations in developmental trajectories of adolescent brain structure, as well as how they relate to later-life outcomes including mental health.