Brief report Meta-analysis shows schizophrenia is not associated with the 40-base-pair repeat polymorphism of the dopamine transporter gene F. Gamma a,b, * , Stephen V. Faraone d , Stephen J. Glatt e , Yu-Chi Yeh c , Ming T. Tsuang e,f a Department of Psychiatry, Harvard Medical School at the Massachusetts Mental Health Center, Boston, MA, USA b Harvard Institute of Psychiatric Epidemiology and Genetics, Harvard Departments of Epidemiology and Psychiatry, Boston, MA, USA c Department of General Psychiatry, Bali Mental Hospital, Department of Health of Taiwan, Taipei County, Taiwan d Medical Genetics Research Center and Department of Psychiatry, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA e Institute of Behavioral Genomics, Department of Psychiatry, University of California, San Diego, La Jolla, CA, USA f VA San Diego Healthcare System, La Jolla, CA, USA Received 9 September 2004; received in revised form 20 September 2004; accepted 20 September 2004 Abstract Objective: Several case-control studies examined an association between schizophrenia and the 40-bp variable number tandem repeat (VTNR) polymorphism in the 3’-UTR of the dopamine transporter gene (SLC6A3). The results of these studies have been equivocal due to small sample size and low power. This meta-analysis has the aim to evaluate the collective evidence for an association between the VTNR polymorphism and schizophrenia. Method: Different meta-analyses were performed, sequentially considering the 9- and 10-repeat alleles and different genotypes (genotypes 9/9, 9/10, 10/10) as risk factors for schizophrenia. Analyses of the alleles included 659 cases and 563 controls from six case-control studies. Results: The pooled OR from each analysis approximated 1.0, and none were significant. Lack of significance attributable to the negative effects of single large studies or to heterogeneity between the studies was excluded. Conclusion: Despite over 90% power to detect a significant odds ratio as small as 1.3, no association was observed. Considering the cumulative evidence from six case-control studies and results from additional family-based studies, it seems unlikely that the 40-base-pair VTNR polymorphism of the SLC6A3 gene influences risk for schizophrenia. D 2004 Elsevier B.V. All rights reserved. Keywords: Meta-analysis; Association; Dopamine; Dopamine transporter gene; Schizophrenia 0920-9964/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2004.09.020 * Corresponding author. Tel.: +617 266 3631. E-mail address: franziska.gamma@verizon.net (F. Gamma). Schizophrenia Research 73 (2005) 55 – 58 www.elsevier.com/locate/schres