title: Association between brain-derived neurotrophic factor genetic polymorphism Val66Met and susceptibility to bipolar disorder: a meta-analysis.
abstract: BACKGROUND
  In view of previous conflicting findings, this meta-analysis was performed to comprehensively determine the overall strength of associations between brain-derived neurotrophic factor (BDNF) genetic polymorphism Val66Met and susceptibility to bipolar disorders (BPD).
  
  
  METHODS
  Literatures published and cited in Pubmed and Wanfang Data was searched with terms of 'Val66Met', 'G196A', 'rs6265', 'BDNF', 'association', and 'bipolar disorder' up to March 2014. All original case-control association studies were meta-analyzed with a pooled OR to estimate the risk and 95% confidence interval (CI) to reflect the magnitude of variance.
  
  
  RESULTS
  Twenty-one case-control association studies met our criteria for the meta-analysis. Overall, there was no significant difference in allelic distribution of Val66Met polymorphism between patients and controls with a pooled OR = 1.03 (95% CI 0.98, 1.08) although there was a trend towards association between Val66Met polymorphism and BPD in Caucasians with an OR of 1.08 (95% CI 1.00, 1.16). However, subgroup analyses showed that there was a significant association of Val allele with decreased disease susceptibility for bipolar disorder type II with a pooled OR of 0.88 (95% CI 0.78, 0.99).
  
  
  CONCLUSIONS
  There is no compelling evidence to supportVal66Met polymorphism in BDNF gene playing an important role in the susceptibility to BPD across different ethnicities.
authors.affiliation: Division of Mood Disorders, Hongkou District Mental Health Center of Shanghai, Shanghai, 200083, P. R. China. wzwhk@163.com.|Division of Mood Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, P. R. China. wzwhk@163.com.
authors.forename: Zuowei
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Neurology, Renji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200127, P. R. China. lizezhi1981@aliyun.com.
authors.forename: Zezhi
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Psychiatry, Mood and Anxiety Clinic in the Mood Disorders Program, University Hospitals Case Medical Center/Case Western Reserve University School of Medicine, Cleveland, Ohio, 44106, USA. Keming.Gao@UHhospitals.org.
authors.forename: Keming
authors.initials: K
authors.lastname: Gao
authors.affiliation: Division of Mood Disorders, Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, 200030, P. R. China. yirufang@aliyun.com.
authors.forename: Yiru
authors.initials: Y
authors.lastname: Fang
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D044466:Asian People / Q000235:genetics; D001714:Bipolar Disorder / Q000235:genetics; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics*; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D006801:Humans; D008715:Methionine / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics*; D014633:Valine / Q000235:genetics; D044465:White People / Q000235:genetics
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D008715:Methionine; D014633:Valine