Given current theoretical understanding of mechanisms that may be implicated in the emergence and maintenance of OCD symptoms and the treatment of the disorder, a number of investigators have pursued genetic studies of specific genes that are known to be involved in systems implicated in the pathogenesis of OCD. In particular, because of the efficacy of serotonin reuptake in treating OCD,78-79 a number of genes important in the serotonergic system have been examined. In addition, genes in the dopaminergic, glutamatergic, and opioid systems have also been studied to determine if they also contribute to the risk of OCD.80