replication sample. As rates of childhood physical abuse were higher in the CATS replication sample, and multiple indices of abuse were available, the factor score provides a more refined characterization of abuse exposure in that sample. It should be noted that replication with a dichotomous and continuously coded environmental exposure measure indicates the robustness of these findings68. (e) The replication sample included heroin-dependent cases and controls matched for neighborhood (i.e. high risk) exposure and rates of anhedonia and abuse in this population exceed the general population. Nonetheless, adjustment for case status did not influence our findings. However it is possible that the mechanisms underlying the relationship between genotype, anhedonia and physical abuse are different in this sample.
