Characterising mental wellbeing and associations with subcortical grey matter volume at short intervals in early adolescence.

This temporally rich, longitudinal study of early adolescents (N = 88, 277 datasets, 12-13 years) investigated the relationship between bilateral subcortical grey matter volume (GMV) in the hippocampus, amygdala, accumbens-area, caudate, putamen and pallidum with self-reported mental wellbeing at four timepoints, across 12 months. Generalised Estimating Equations (GEE) revealed (1) higher 'total wellbeing' was associated with smaller left caudate and larger left accumbens-area; (2) higher eudaimonic wellbeing was associated with smaller left caudate and larger right caudate; and (3) higher hedonic wellbeing was associated with larger left accumbens-area. Further analyses and plots highlighted different associations between GMV and wellbeing for adolescents who consistently experienced 'moderate-to-flourishing' wellbeing (n = 63, 201 datasets), compared with those who experienced 'languishing' wellbeing at any timepoint (n = 25, 76 datasets). These findings demonstrate several associations between subcortical GMV and measures of wellbeing, at short intervals in early adolescence. Taken together, sub-types of wellbeing appear uniquely associated with specific subcortical regions; and there may be a distinct neurobiological and wellbeing profile for adolescents who experience poorer wellbeing over the course of their first year(s) of secondary school. This study implicates the bilateral caudate and left accumbens-area as important targets for future research into the mental wellbeing of adolescents.