Logistic regression analyses were performed to determine the effects of all four GABRA2 haplotypes and childhood trauma (total CTQ score) on alcohol, cocaine and heroin dependence. The results are presented in Table 2. Childhood trauma had a significant effect on patients with alcohol dependence and cocaine dependence but there was no gene effect. There was a significant effect of childhood trauma and the 2111111 haplotype in the total group of patients with substance dependence. Childhood trauma had no effect in the total group of individuals with heroin dependence however haplotypes 2111111 and 2112122 both had significant effects. The direction of the haplotypic effects can be discerned from Table 1: haplotype 2112122 was more abundant in individuals with heroin dependence whereas haplotype 2111111 was more common in controls compared with individuals with alcohol, heroin or cocaine dependence. The full model contributed to 10% of the variance in any addiction and up to 13% of the variance for heroin addiction alone: in both of these models, genetic and environmental effects had a significant impact.
