Directionality of longitudinal associations between frontostriatal structural connectivity and depressive symptoms in adolescent girls

BACKGROUND: Individual differences in the structure and function of the frontostriatal reward network have been related to depression. However, there is a strong need for prospective, longitudinal studies aiming to understand the role of frontostriatal networks in depression in a developmental context. We aimed to examine bidirectional associations between structural connectivity in the frontostriatal reward network and depressive symptoms in adolescent girls, as well as to determine to what extent the directionality and strength of these associations are dependent on age or pubertal stage. METHODS: About 596 observations from 174 adolescent girls (up to 4 time points per person, ages 10-17) were included. Depressive symptoms were measured with the Center for Epidemiological Studies-Depression scale for Children and pubertal stage with the Pubertal Development Scale and the Tanner Stage Line Drawings. Probabilistic tractography was done on diffusion-weighted imaging scans to obtain average fractional anisotropy from ventral striatum to orbitofrontal cortex and ventral striatum to ventromedial prefrontal cortex tracts. RESULTS: Linear mixed-effects models showed that frontostriatal connectivity was not associated with subsequent change in depressive symptoms. Depressive symptoms were also not associated with subsequent change in frontostriatal connectivity. Depressive symptoms increased with age and pubertal stage, but the association with connectivity did not vary with age or pubertal stage. CONCLUSIONS: This suggests previously reported cross-sectional associations might not pertain to developmental effects in girls. Future research should examine prospective associations between frontostriatal functional connectivity and depression.