In conclusion, the present study has shown that childhood trauma is a strong predictor for alcohol, cocaine and heroin dependence in African American men. Together with childhood trauma, GABRA2 variation influences risk and resilience for all addiction but most strongly for heroin dependence. Our results suggest that GABRA2 may have at least two independent loci that are implicated in the vulnerability to heroin addiction. The two GABRA2 risk – resilience haplotypes are unique to African Americans. There were no findings with the yin-yang haplotypes that confer addiction risk in Caucasians. Moreover, since there is evidence for sexual dimorphism in the influence of GABRA2 on addiction vulnerability with previous results being significant only in men (16), the results of our study may not extend to African American women. Thus the findings of the present study may be unique to African-American men and await replication in other similar datasets.
