White matter changes in late-life depression: a diffusion tensor imaging study.

BACKGROUND: Numerous studies have revealed white matter abnormalities in late-life depression (LLD). The objective was to investigate the integrity of white matter tracts in subjects with LLD compared to similar aged healthy individuals using diffusion tensor imaging (DTI).
METHODS: Sixty eight subjects (30 healthy individuals, 38 depressed) underwent DTI on a 3T scanner following clinical and cognitive assessment. An automated tract-based spatial statistics (TBSS) method was used to derive estimates of fractional anisotropy (FA) and mean diffusivity (MD) for each subject. Group effects and correlations with clinical features on DTI parameters were examined.
RESULTS: Compared to controls, uncorrected maps revealed patients with LLD exhibited lower FA in frontal, temporal and midbrain regions relative to older healthy subjects (p<0.05). However, using corrected maps no significant differences were observed in LLD patients in FA and MD parameters (p<0.05, family-wise error corrected for multiple comparisons). Regression analyses revealed no significant relationship between DTI parameters and current depressive symptoms in LLD (p>0.05, uncorrected and corrected).
CONCLUSIONS: Findings are suggestive of loss of integrity in white matter fibres within frontal, temporal and midbrain regions, increasing the evidence that implicates disruptions to the limbic-orbitofrontal networks in the pathogenesis of LLD. However, as results did not survive strict control for multiple comparisons, they should be considered tentative and replication in larger cohorts is needed.