Introduction 2002 DRD4 1992 1993 1997 1991 1995 1993 1998 1995 DRD4 1992 1996 1996 2001 1996 1998 1996 2000 2005 2001 DRD4 2004 1999 1999 2003 1998 2001 1997 2006 2001 1995 DRD4 DRD4 Materials and methods Subjects Samples from 570 unrelated cases of schizophrenia (285 men, 285 women; mean age 47.0±11.4 years), and 570 age and sex matched controls (285 men, 285 women; mean age 46.7±11.1 years) were analyzed. The diagnosis of schizophrenia was made by consultation according to DSM-IV criteria with consensus from at least two experienced psychiatrists. All available medical records were taken into consideration. Control subjects were recruited from hospital staff and volunteers who showed no evidence of present or past psychoses during brief interviews with psychiatrists. All subjects were from central Japan. The study was approved by the Ethics Committees of RIKEN, Hamamatsu University and Chiba University. All participants provided written informed consent. Sequence analysis DRD4 Genotyping 1 Fig. 1 DRD4 boxes white black solid squares triangles  Statistical analyses The allelic and genotypic distributions were tested for association by Fisher’s exact test for biallelic markers (SNPs, the 120-bp tandem duplication and the 12-bp repeat polymorphism). http://www.rfcgr.mrc.ac.uk/∼fdudbrid/software/unphased/ 2003 D http://www.broad.mit.edu/mpg/haploview/ 2005 Logistic regression analysis 2002 x 1 x 2 x 1 x 2 Results DRD4 1 1 Table 1 DRD4 Marker dbSNP ID Physical position Case or control n Genotype frequencies P P  – 625826–626065   1/1 1/2 2/2   Case 569 0.04  0.32  0.64  0.202  0.377  Control 570 0.06  0.34  0.61  −1106 T>C rs936460 626199   T/T T/C C/C   Case 569 0.79  0.20  0.02  0.522  0.644  Control 570 0.76  0.22  0.02  −906 T>C rs3758653 626399   T/T T/C C/C   Case 569 0.66  0.31  0.03  0.116  0.223  Control 569 0.62  0.34  0.05  −809 G>A rs936461 626496   A/A A/G G/G   Case 562 0.03  0.33  0.64  0.018  0.032  Control 564 0.06  0.35  0.59  −616 G>C rs747302 626689   C/C C/G G/G   Case 565 0.09  0.44  0.47  0.769  0.257  Control 568 0.10  0.39  0.50  −521 T>C rs1800955 626784   T/T T/C C/C   Case 566 0.34  0.48  0.19  0.371  0.377  Control 569 0.34  0.50  0.16  −376 C>T rs916455 626929   T/T T/C C/C   Case 561 0.01  0.18  0.81  0.732  0.838  Control 562 0.01  0.19  0.80  −291 C>T rs916457 627014   T/T T/C C/C   Case 565 0.01  0.21  0.79  0.518  0.080  Control 566 0.02  0.19  0.79   rs4646983 627392–627391   a a a   Case 568 0.02  0.25  0.73  0.512  0.248  Control 569 0.03  0.21  0.76  a P P D 2 2 Fig. 2 DRD4 D D D D  Table 2 DRD4 Marker β SE χ 2 P OR OR 95% CI −809G>A 0.346  0.127  7.384  0.007  1.414  1.10–1.82 −616G>C 0.247  0.125  3.872  0.049  1.280  1.00–1.64 −291C>T 1.031  0.400  6.649  0.010  2.804  1.28–6.24 12-bp repeat −0.725  0.274  6.988  0.008  0.484  0.28–0.83 β SE Wald χ 2 OR CI Discussion DRD4 1999 2004 2001 2003 DRD4 DRD4 2000 2006 2003 2003 DRD4