title: The power of sample size and homogenous sampling: association between the 5-HTTLPR serotonin transporter polymorphism and major depressive disorder.
abstract: BACKGROUND
  Several lines of evidence indicate that abnormalities in the functioning of the central serotonergic system are involved in the pathogenesis of affective illness. A 44-base-pair insertion/deletion polymorphism in the 5' regulatory region of the serotonin transporter gene (5-HTTLPR), which influences expression of the serotonin transporter, has been the focus of intensive research since an initial report on an association between 5-HTTLPR and depression-related personality traits. Consistently replicated evidence for an involvement of this polymorphism in the etiology of mood disorders, particularly in major depressive disorder (MDD), remains scant.
  
  
  METHODS
  We assessed a potential association between 5-HTTLPR and MDD, using the largest reported sample to date (466 patients, 836 control subjects). Individuals were all of German descent. Patients were systematically recruited from consecutive inpatient admissions. Control subjects were drawn from random lists of the local Census Bureau and screened for psychiatric disorders.
  
  
  RESULTS
  The short allele of 5-HTTLPR was significantly more frequent in patients than in control subjects (45.5% vs. 39.9%; p = .006; odds ratio = 1.26).
  
  
  CONCLUSIONS
  These results support an involvement of 5-HTTLPR in the etiology of MDD. They also demonstrate that the detection of small genetic effects requires very large and homogenous samples.
authors.affiliation: Department of Psychiatry, University of Bonn, Germany.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hoefgen
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Schulze
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ohlraun
authors.forename: Olrik
authors.initials: O
authors.lastname: von Widdern
authors.forename: Susanne
authors.initials: S
authors.lastname: Höfels
authors.forename: Magdalena
authors.initials: M
authors.lastname: Gross
authors.forename: Vivien
authors.initials: V
authors.lastname: Heidmann
authors.forename: Svetlana
authors.initials: S
authors.lastname: Kovalenko
authors.forename: Anita
authors.initials: A
authors.lastname: Eckermann
authors.forename: Heike
authors.initials: H
authors.lastname: Kölsch
authors.forename: Martin
authors.initials: M
authors.lastname: Metten
authors.forename: Astrid
authors.initials: A
authors.lastname: Zobel
authors.forename: Tim
authors.initials: T
authors.lastname: Becker
authors.forename: Markus M
authors.initials: MM
authors.lastname: Nöthen
authors.forename: Peter
authors.initials: P
authors.lastname: Propping
authors.forename: Reinhard
authors.initials: R
authors.lastname: Heun
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Maier
authors.forename: Marcella
authors.initials: M
authors.lastname: Rietschel
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003865:Major Depressive Disorder / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics*; D008875:Middle Aged; D009419:Nerve Tissue Proteins / Q000235:genetics*; D010641:Phenotype; D011110:Polymorphism, Genetic; D050486:Serotonin Plasma Membrane Transport Proteins
chemical_list: D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C493230:SLC6A4 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins