The three countries were significantly different in their rates of DD (χ2=18.349, p<0.001). When binary logistic regression was used to analyze country of residence Mexico and Central American schizophrenic patients were less likely to be diagnosed with SUD than subjects from the US (Mexico: B=−1.337, Wald χ2=17.225, df= 1, p<0.001, odd ratios=0.263; Central American: B=−0.818, Wald χ2=4.444, df=1, p=0.035, odd ratios=0.441); therefore, country of residence was a significant predictor of SUD.
