Association analysis between the A118G polymorphism in the OPRM1 gene and treatment response to venlafaxine XR in generalized anxiety disorder

Patients diagnosed with generalized anxiety disorder (GAD) exhibit differential responses to standard antidepressant pharmacotherapy. Mounting evidence demonstrates that genetic differences may be implicated in treatment response in disorders like GAD. In this study, we examined whether the OPRM1 gene, which has been implicated in antidepressant treatment response in major depressive disorder, also has an effect in GAD. In our study, 156 patients diagnosed with GAD received venlafaxine XR treatment as part of an 18-month relapse prevention study. Genotypes were obtained for the OPRM1 functional variant A118G for the entire sample (n=151); however, only the European American population was considered (n=108) for pharmacogenetic analysis. We found no significant association between A118G and antidepressant treatment response in our GAD population. Future studies that include different single nucleotide polymorphisms of the OPRM1 gene as well as larger populations will need to be conducted to further elucidate the pharmacogenetic role of the endogenous opioid system in anxiety disorders. Copyright (c) 2013 John Wiley & Sons, Ltd.