title: Amygdala volumes in mood disorders--meta-analysis of magnetic resonance volumetry studies.
abstract: BACKGROUND
  The amygdala plays an important role in the regulation of emotions and has been implicated in the pathophysiology of mood disorders. Studies of amygdala volumes in mood disorders have been conflicting, with findings of increased, decreased and unchanged amygdala volumes in patients relative to controls. We present the largest meta-analysis of amygdala volumes in mood disorders and the first one to investigate modifying effects of clinical, demographic and methodological variables.
  
  
  METHODS
  We reviewed 40 magnetic resonance imaging studies investigating amygdala volumes in patients with unipolar or bipolar disorders. For meta-analysis we used standardized differences in means (SDM) and random effect models. In the search for sources of heterogeneity, we subdivided the studies based on diagnosis, setting, age, medication status, sex, duration of illness, slice thickness, interrater reliability of tracing and anatomical definitions used.
  
  
  RESULTS
  The volumes of the left and right amygdala in bipolar (N=215) or unipolar (N=409) patients were comparable to controls. Bipolar children and adolescents had significantly smaller left amygdala volumes relative to controls (SDM=-0.34, 95%CI=-0.65; -0.04, z=-2.20, p=0.03), whereas bipolar adults showed a trend for left amygdala volume increases (SDM=0.46, 95%CI=-0.03; 0.96, z=1.83, p=0.07). Unipolar inpatients had significantly larger left (SDM=0.35, 95%CI=0.03; 0.67, z=-2.17, p=0.03) amygdala volumes than controls, with no significant amygdala volume changes in unipolar outpatients.
  
  
  CONCLUSIONS
  Heterogeneity of included studies.
  
  
  CONCLUSIONS
  The absence of overall differences in amygdala volumes, in the presence of significant and sometimes mirror changes in patient subgroups, demonstrates marked heterogeneity among mood disorders. Amygdala volume abnormalities may not be associated with mood disorders per se, but rather may underlie only some dimensions of illness or represent artifacts of medication or comorbid conditions.
authors.affiliation: Department of Psychiatry, Dalhousie University, Halifax, Nova Scotia, Canada. tomas.hajek@dal.ca
authors.forename: Tomas
authors.initials: T
authors.lastname: Hajek
authors.forename: Miloslav
authors.initials: M
authors.lastname: Kopecek
authors.forename: Jiri
authors.initials: J
authors.lastname: Kozeny
authors.forename: Eva
authors.initials: E
authors.lastname: Gunde
authors.forename: Martin
authors.initials: M
authors.lastname: Alda
authors.forename: Cyril
authors.initials: C
authors.lastname: Höschl
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000679:Amygdala / Q000473:pathology* / Q000503:physiopathology; D001714:Bipolar Disorder / Q000473:pathology; D001931:Brain Mapping / Q000379:methods; D002648:Child; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D019964:Mood Disorders / Q000473:pathology* / Q000503:physiopathology