Within the logistic regression analysis for the total group of patients and controls, the comparison of haplotype 2111111 with the other three haplotypes showed a trend interactive effect with CTQ scores (p = 0.087). Therefore we asked whether the protective effect of haplotype 2111111 might differ with exposure to childhood adversity. In secondary analyses we used the dichotomous CTQ high/low variable (high childhood adversity designated as CTQ total score ≥ 1 S.D. above mean score of controls; low adversity being < 1 S.D. above mean CTQ score of controls). Figure 3 shows that carriers of the other three haplotypes who had been exposed to high childhood adversity were predictably more likely to have developed substance dependence than those exposed to low childhood adversity (χ2 = 6.7 – 11, p = 0.009 – 0.0009, 1df). In carriers of the 2111111 haplotype, high childhood adversity was associated with a numerically higher but non-significant (p = 0.44) frequency of addiction indicating that this haplotype may confer resilience to childhood adversity.
