title: BDNF Val66Met polymorphism and hippocampal volume in neuropsychiatric disorders: A systematic review and meta-analysis.
abstract: BACKGROUND
  Brain-derived neurotrophic factor (BDNF) is a neurotrophin involved in neurogenesis and synaptic plasticity in the central nervous system, especially in the hippocampus, and has been implicated in the pathophysiology of several neuropsychiatric disorders. Its Val66Met polymorphism (refSNP Cluster Report: rs6265) is a functionally relevant single nucleotide polymorphism affecting the secretion of BDNF and is implicated in differences in hippocampal volumes.
  
  
  METHODS
  This is a systematic meta-analytical review of findings from imaging genetic studies on the impact of the rs6265 SNP on hippocampal volumes in neuropsychiatric patients with major depressive disorder, anxiety, bipolar disorder or schizophrenia.
  
  
  RESULTS
  The overall sample size of 18 independent clinical cohorts comprised 1695 patients. Our results indicated no significant association of left (Hedge's g=0.08, p=0.12), right (g=0.07, p=0.22) or bilateral (g=0.07, p=0.16) hippocampal volumes with BDNF rs6265 in neuropsychiatric patients. There was no evidence for a publication bias or any demographic, clinical, or methodological moderating effects. Both Val/Val homozygotes (g=0.32, p=0.004) and Met-carriers (g=0.20, p=0.004) from the patient sample had significantly smaller hippocampal volumes than the healthy control sample with the same allele. The magnitude of these effects did not differ between the two genotypes.
  
  
  CONCLUSIONS
  This meta-analysis suggests that there is no association between this BDNF polymorphism and hippocampal volumes. For each BDNF genotype, the hippocampal volumes were significantly lower in neuropsychiatric patients than in healthy controls.
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Harrisberger
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Smieskova
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Schmidt
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Lenz
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Walter
authors.affiliation: German Centre for Neurodegenerative Diseases (DZNE), Rostock/Greifswald, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Wittfeld
authors.affiliation: German Centre for Neurodegenerative Diseases (DZNE), Rostock/Greifswald, Germany; Department of Psychiatry and Psychotherapy, University Medicine Greifswald, Helios Hospital Stralsund, Stralsund, Germany.
authors.forename: H J
authors.initials: HJ
authors.lastname: Grabe
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland.
authors.forename: U E
authors.initials: UE
authors.lastname: Lang
authors.affiliation: King's College London, Department of Psychosis Studies, Institute of Psychiatry Psychology and Neuroscience, De Crespigny Park 16, SE58AF London, UK; OASIS Prodromal Team SLaM NHS Foundation Trust, London, UK.
authors.forename: P
authors.initials: P
authors.lastname: Fusar-Poli
authors.affiliation: University of Basel, Department of Psychiatry (UPK), Wilhelm Klein-Strasse 27, 4056 Basel, Switzerland; University of Basel, Department of Clinical Research (DKF), 4031 Basel, Switzerland; King's College London, Department of Psychosis Studies, Institute of Psychiatry Psychology and Neuroscience, De Crespigny Park 16, SE58AF London, UK. Electronic address: stefan.borgwardt@upkbs.ch.
authors.forename: S
authors.initials: S
authors.lastname: Borgwardt
mesh_terms: D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics*; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D001523:Mental Disorders / Q000235:genetics* / Q000473:pathology*; D008715:Methionine / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D014633:Valine / Q000235:genetics
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D008715:Methionine; D014633:Valine
keywords: Anxiety disorders; BDNF; BDNF Val66Met; Bipolar disorder; Brain-derived neurotrophic factor; Depression; Hippocampus; MRI; Meta-analysis; Neuropsychiatric patients; Schizophrenia; Structural; rs6265