Depressive symptom severity is associated with increased cortical thickness in older adults.

OBJECTIVE: Structural neuroimaging studies in older adults have consistently shown volume reductions in both major and subthreshold depression. Cortical thickness, another measure of brain structure, has not been well studied in this population. We examined cortical thickness in older adults across a range of depressive symptom (DS) severity.
METHODS: Forty-three community-dwelling older adults (mean age = 68.80 ± 7.00 years) underwent magnetic resonance imaging. Based on a priori hypotheses, we examined cortical thickness in regions of interest in the rostral anterior cingulate, orbitofrontal cortex, middle frontal gyrus, and isthmus cingulate using multiple linear regressions with depression questionnaire scores as the independent variable and age, sex, and mean hemispheric thickness as covariates. We also performed an exploratory vertex-wise analysis.
RESULTS: After correction for multiple comparisons, we found an association between increased DSs and greater cortical thickness in the right isthmus cingulate (F(1, 38) = 8.09, false discovery rate corrected p = 0.028; R(2) = 35.78) in the region of interest analysis and in the left precuneus (cluster size = 413, p = 0.00002) in the vertex-wise analysis.
CONCLUSIONS: Older adults with higher DSs also have greater cortical thickness in the isthmus cingulate and precuneus, areas important for emotion regulation and self-referential processing. Additional research is needed to elucidate the mechanisms and potential clinical significance underlying this relationship.