Given the complexity of the OCD phenotype, it is highly unlikely that any of the candidate genes examined to date will be significant, unique risk factors for OCD. Thus, although they may truly be associated with the onset, severity, or persistence of OCD symptoms, they are unlikely to cause OCD without the presence of other risk genes. On the other hand, since most current effective pharmacologic agents target the serotonergic and dopaminergic systems, it is possible that some of the genes in those systems could play a role in treatment response. Knowing which genes impact treatment response would be a major advance in the treatment of OCD and is consistent with the primary goal of the emerging field of pharmacogenetics. However, it would not necessarily demonstrate that those genes are involved in the etiology of OCD. Genes involved in response to treatment may not be involved in the etiology of a disorder.
