title: Structural neuroimaging studies in major depressive disorder. Meta-analysis and comparison with bipolar disorder.
abstract: BACKGROUND
  Although differences in clinical characteristics exist between major depressive disorder (MDD) and bipolar disorder (BD), consistent structural brain abnormalities that distinguish the disorders have not been identified.
  
  
  OBJECTIVE
  To investigate structural brain changes in MDD using meta-analysis of primary studies; assess the effects of medication, demographic, and clinical variables; and compare the findings with those of a meta-analysis of studies on BD.
  
  
  METHODS
  The MEDLINE, EMBASE, and PsycINFO databases were searched for studies from January 1, 1980, to February 2, 2010.
  
  
  METHODS
  Two hundred twenty-five studies that used magnetic resonance imaging or x-ray computed tomography to compare brain structure in patients with MDD with that of controls were included in an online database, and 143 that measured common brain structures were selected for meta-analysis.
  
  
  METHODS
  Twenty-five variables, including demographic and clinical data, were extracted from each study, when available. For the meta-analysis, mean structure size and standard deviation were extracted for continuous variables, and the proportion of patients and controls with an abnormality in brain structure was extracted for categorical variables.
  
  
  RESULTS
  Compared with the structure of a healthy brain, MDD was associated with lateral ventricle enlargement; larger cerebrospinal fluid volume; and smaller volumes of the basal ganglia, thalamus, hippocampus, frontal lobe, orbitofrontal cortex, and gyrus rectus. Patients during depressive episodes had significantly smaller hippocampal volume than patients during remission. Compared with BD patients, those with MDD had reduced rates of deep white matter hyperintensities, increased corpus callosum cross-sectional area, and smaller hippocampus and basal ganglia. Both disorders were associated with increased lateral ventricle volume and increased rates of subcortical gray matter hyperintensities compared with healthy controls.
  
  
  CONCLUSIONS
  The meta-analyses revealed structural brain abnormalities in MDD that are distinct from those observed in BD. These findings may aid investigators attempting to discriminate mood disorders using structural magnetic resonance imaging data.
authors: Department of Neuroimaging, PO89, Institute of Psychiatry, King's College London, De Crespigny Park, London SE5 8AF, England. matthew.kempton@kcl.ac.uk
authors: Matthew J
authors: MJ
authors: Kempton
authors: Zainab
authors: Z
authors: Salvador
authors: Marcus R
authors: MR
authors: Munafò
authors: John R
authors: JR
authors: Geddes
authors: Andrew
authors: A
authors: Simmons
authors: Sophia
authors: S
authors: Frangou
authors: Steven C R
authors: SC
authors: Williams
mesh_terms: D001479:Basal Ganglia / Q000000981:diagnostic imaging / Q000473:pathology; D001714:Bipolar Disorder / Q000134:cerebrospinal fluid / Q000000981:diagnostic imaging / Q000473:pathology*; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology*; D003865:Major Depressive Disorder / Q000134:cerebrospinal fluid / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D005625:Frontal Lobe / Q000000981:diagnostic imaging / Q000473:pathology; D006624:Hippocampus / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D013788:Thalamus / Q000000981:diagnostic imaging / Q000473:pathology; D014057:Tomography, X-Ray Computed