title: Allelic and genotypic associations of DRD2 TaqI A polymorphism with heroin dependence in Spanish subjects: a case control study.
abstract: BACKGROUND
  Conflicting associations with heroin dependence have been found involving the A1 allele of dopamine D2 receptor gene (DRD2) TaqI A polymorphism.
  
  
  METHODS
  We compared two samples of unrelated Spanish individuals, all of European origin: 281 methadone-maintained heroin-dependent patients (207 males and 74 females) who frequently used non-opioid substances, and 145 control subjects (98 males and 47 females).
  
  
  RESULTS
  The A1-A1 genotype was detected in 7.1% of patients and 1.4% of controls (P = 0.011, odds ratio = 5.48, 95% CI 1.26-23.78). Although the A1 allele was not associated with heroin dependence in the entire sample, the frequency of A1 allele was higher in male patients than in male controls (24.4% vs. 16.3%, P = 0.024, odds ratio = 1.65, 95% CI 1.07-2.57). A logistic regression analysis showed an interaction between DRD2 alleles and gender (odds ratio = 1.77, 95% CI 1.15-2.70).
  
  
  CONCLUSIONS
  Our results indicate that, in Spanish individuals, genotypes of the DRD2 TaqI A polymorphism contribute to variations in the risk of heroin dependence, while single alleles contribute only in males.
authors.affiliation: Addictive Behaviours Unit of Psychiatry Department, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain. jperezc@santpau.es
authors.forename: Jose
authors.initials: J
authors.lastname: Perez de los Cobos
authors.forename: Montserrat
authors.initials: M
authors.lastname: Baiget
authors.forename: Joan
authors.initials: J
authors.lastname: Trujols
authors.forename: Nuria
authors.initials: N
authors.lastname: Sinol
authors.forename: Victor
authors.initials: V
authors.lastname: Volpini
authors.forename: Enrique
authors.initials: E
authors.lastname: Banuls
authors.forename: Francesc
authors.initials: F
authors.lastname: Calafell
authors.forename: Elena
authors.initials: E
authors.lastname: Luquero
authors.forename: Elisabeth
authors.initials: E
authors.lastname: del Rio
authors.forename: Enric
authors.initials: E
authors.lastname: Alvarez