title: The Val66Met polymorphism of the BDNF gene in anorexia nervosa: new data and a meta-analysis.
abstract: OBJECTIVE
  The Val66Met polymorphism (rs6265) of the BDNF gene is a non-synonymous polymorphism, previously associated with anorexia nervosa (AN).
  
  
  METHODS
  We genotyped rs6265 in 235 patients with AN and 643 controls. Furthermore, we performed a systematic review of all case-control and family-based studies testing this SNP in AN, and combined the results in a meta-analysis.
  
  
  RESULTS
  The results of the case-control study were non-significant. For the meta-analysis, nine studies were identified (ncases = 2,767; ncontrols = 3,322, ntrios = 53) and included. Primarily, the analyses indicated an association with OR of 1.11 (P = 0.024) in the allelic contrast, and OR of 1.14 (P = 0.025) for the dominant effect of the Met allele. However, additional analyses revealed that the first published study (from those included in the meta-analysis) overly influenced the pooled effect size (possibly due to a phenomenon known as a winner's curse). When this case-control study was replaced by a trio study (ntrios = 293) performed on a largely overlapping sample, the effect size became smaller and non-significant, both for the allelic contrast (OR = 1.07, P = 0.156) and the dominant effect (OR = 1.07, P = 0.319). The quality of included studies was good and there was no significant heterogeneity across the effect sizes.
  
  
  CONCLUSIONS
  Our analyses indicate that the BDNF Val66Met variant is not associated with AN at detectable levels.
authors.affiliation: Department of Neuroscience & Pharmacology, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marek K
authors.initials: MK
authors.lastname: Brandys
authors.forename: Martien J H
authors.initials: MJ
authors.lastname: Kas
authors.forename: Annemarie A
authors.initials: AA
authors.lastname: van Elburg
authors.forename: Roel
authors.initials: R
authors.lastname: Ophoff
authors.forename: Margarita C T
authors.initials: MC
authors.lastname: Slof-Op't Landt
authors.forename: Christel M
authors.initials: CM
authors.lastname: Middeldorp
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
authors.forename: Eric F
authors.initials: EF
authors.lastname: van Furth
authors.forename: P Eline
authors.initials: PE
authors.lastname: Slagboom
authors.forename: Roger A H
authors.initials: RA
authors.lastname: Adan
mesh_terms: D000328:Adult; D000483:Alleles; D000856:Anorexia Nervosa / Q000235:genetics*; D019208:Brain-Derived Neurotrophic Factor / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D005838:Genotype; D006801:Humans; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D055815:Young Adult
chemical_list: D019208:Brain-Derived Neurotrophic Factor; C579455:BDNF protein, human