Heterogeneity Q tests were also performed to evaluate possible differences in OR between the studies using the World Health Organization’s International Statistical Classification of Diseases and Related Health Problems (ICD)(World Health Organization) or the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM)(American Psychiatric Association) system and others criteria(allowing the inclusion of the studies with no description of specific criteria); between the studies with specified criteria and the studies with no description of criteria; between the English-language publications and Chinese-language publications; between the studies originating in mainland China and others (identified by information provided, e.g., institutions and addresses of the authors); and between the studies originating in the United States and others. The results showed that there was no evidence of significant heterogeneity in the Asian studies regarding different diagnostis criteria, publication languages, or research sites using either allelic or genotypic analysis. The results are shown in supplementary Table 2 (P(Q) > 0.1).
