The results of the current study generate interesting hypotheses about the mechanism of recovery and may have implications for understanding the assorted responses to pharmacotherapy. Both naltrexone and acamprosate have been shown in numerous clinical studies to have efficacy in reducing relapse among alcohol-dependent individuals. Despite the better group response to pharmacotherapy in clinical trials, there is significant variability in response among individuals treated with medication. While some of this variability is due to differences in adherence and obtaining a functionally significant dose (McCaul et al., 1997; Pettinati and Rabinowitz, 2005), there remain intra-individual differences in patient response that have not yet been accounted for or predicted. If it were possible to isolate variables that could predict a greater likelihood of positive response to the medication, it would be possible to use the medication with greater certainty and efficiency. This is the basis of much of the contemporary effort in the field of pharmacogenetics (Evans and Relling, 1999). Thus, a critical question remains: for which patients will pharmacotherapy have the greatest benefit? For naltrexone, there are two studies suggesting specific
