Abstract
Previous reports of altered grey and white matter structure in Major Depressive Disorder (MDD) have been inconsistent. Recent meta-analyses have, however, reported reduced hippocampal grey matter volume in MDD and reduced white matter integrity in several brain regions. The use of different diagnostic criteria, scanners and imaging sequences may, however, obscure further anatomical differences. In this study, we tested for differences in subcortical grey matter volume (n = 1157) and white matter integrity (n = 1089) between depressed individuals and controls in the subset of 8590 UK Biobank Imaging study participants who had undergone depression assessments. Whilst we found no significant differences in subcortical volumes, significant reductions were found in depressed individuals versus controls in global white matter integrity, as measured by fractional anisotropy (FA) (β = −0.182, p = 0.005). We also found reductions in FA in association/commissural fibres (β = −0.184, pcorrected = 0.010) and thalamic radiations (β = −0.159, pcorrected = 0.020). Tract-specific FA reductions were also found in the left superior longitudinal fasciculus (β = −0.194, pcorrected = 0.025), superior thalamic radiation (β = −0.224, pcorrected = 0.009) and forceps major (β = −0.193, pcorrected = 0.025) in depression (all betas standardised). Our findings provide further evidence for disrupted white matter integrity in MDD.
Highlights
Many brain imaging studies have measured grey matter volume differences between healthy individuals and, predominantly clinically ascertained, individuals with Major Depressive Disorder (MDD)
We found no significant group effect for intracranial volume (ICV) based on the principal definition of MDD (β = −0.046, puncorrected = 0.341)
We sought to determine whether MDD was associated with differences in subcortical grey matter volume or white matter integrity in a large imaging dataset from a single scanner of more than 8000 people, and among them over 1000 were included as cases and controls in the analyses for the present study
Summary
Many brain imaging studies have measured grey matter volume differences between healthy individuals and, predominantly clinically ascertained, individuals with MDD. Some studies reported decreased white matter integrity in tracts that connect prefrontal areas (e.g. fronto-occipital fasciculus, superior longitudinal fasciculus)[16]. Meta-analyses of white matter integrity measures in MDD have reported FA reductions in superior longitudinal fasciculus, fronto-occipital fasciculus, and thalamic radiations[17, 18]. These studies, often require the combination of imaging data from different scanners, using different ascertainment criteria and methodology, different clinical instruments and have differing levels of phenotypic data to pursue further research questions. Meta-analytic findings highlight the pressing need to measure brain structural abnormalities in MDD using larger single-scanner samples where robust conclusions can be made in the absence of differing study methodologies
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