Meta-analysis of ACE gene I/D polymorphism and bipolar disorder susceptibility

BACKGROUND: A number of studies have been conducted to explore the association between ACE gene insertion/deletion (I/D) polymorphism and bipolar disorder (BPD). However, the reported results were conflicting. AIMS: The aim of our study was to find evidence on whether ACE gene I/D polymorphism is associated with BPD using a meta-analysis. METHODS: Data were collected from the following electronic databases: Pubmed, Elsevier Science Direct, Cochrane Library, CBM, CNKI and Wanfang. Meta-analysis was performed for genotypes ID vs. II, DD vs. II, DD vs. ID + II, ID + DD vs. II, and D allele vs. I allele in a fixed/random effect model. RESULTS: Seven studies that included data from 605 cases and 1541 controls were identified. When all groups were pooled, we did not detect the association of ACE gene I/D polymorphism with BPD (P > 0.05). In the subgroup analysis, we did not detect the association of ACE gene I/D polymorphism with BPD in Caucasians (P > 0.05). An association of ACE gene I/D polymorphism with BPD was found in Asians for the contrast of DD vs. ID + II (OR = 2.01, 95% CI 1.08-3.74, P = 0.03), but not for other contrasts (P > 0.05). CONCLUSIONS: This meta-analysis suggests that there may be an association of ACE gene I/D polymorphism with BPD in Asians. Further studies are still needed in Asians.