Is depression a disconnection syndrome? Meta-analysis of diffusion tensor imaging studies in patients with MDD.
BACKGROUND
Many studies using diffusion tensor imaging (DTI) have demonstrated impaired white matter integrity in patients with major depressive disorder (MDD), with significant results found in diverse brain regions. We sought to identify whether there are consistent changes of regional white matter integrity in patients with MDD, as shown by decreased fractional anisotropy in DTI.


METHODS
A systematic search strategy was used to identify relevant whole brain voxel-based DTI studies of patients with MDD in relation to comparison groups. Relevant databases were searched for studies published between January 1994 and February 2011 using combinations of the terms "DTI" or "diffusion tensor;" "whole brain" or "voxel-based;" and "depress*." Using the studies that met our inclusion criteria, we performed a meta-analysis of the coordinates of decreased fractional anisotropy using the activation likelihood estimation (ALE) method, which detects 3-dimensional conjunctions of coordinates from multiple studies, weighted by sample size. We then used DTIquery software for fibre tracking to locate the fascicles involved in each region.


RESULTS
We included 11 studies with a combined sample of 231 patients with MDD and 261 comparison participants, providing 50 coordinates of decreased fractional anisotropy. Our meta-analysis identified 4 consistent locations of decreased fractional anisotropy in patients with MDD: white matter in the right frontal lobe, right fusiform gyrus, left frontal lobe and right occipital lobe. Fibre tracking showed that the main fascicles involved were the right inferior longitudinal fasciculus, right inferior fronto-occipital fasciculus, right posterior thalamic radiation and interhemispheric fibres running through the genu and body of the corpus callosum.


CONCLUSIONS
The number of studies included was relatively small, and the DTI data acquisition and analysis techniques were heterogeneous. The ALE method cannot handle studies with no significant group differences.


CONCLUSIONS
Voxel-based analysis of DTI studies of patients with MDD consistently identified decreased fractional anisotropy in the white matter fascicles connecting the prefrontal cortex within cortical (frontal, temporal and occipital lobes) and subcortical areas (amygdala and hippocampus). This isstrong evidence for the involvement of these neural circuits in the pathology of MDD.
Huaxi MR Research Center, Department of Radiology, West China Hospital of Sichuan University, Chengdu, China.
Yi
Y
Liao
Xiaoqi
X
Huang
Qizhu
Q
Wu
Chuang
C
Yang
Weihong
W
Kuang
Mingying
M
Du
Su
S
Lui
Qiang
Q
Yue
Raymond C K
RC
Chan
Graham J
GJ
Kemp
Qiyong
Q
Gong
D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D001931:Brain Mapping / Q000379:methods; D003337:Corpus Callosum / Q000473:pathology; D003865:Major Depressive Disorder / Q000473:pathology*; D056324:Diffusion Tensor Imaging / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male