There is still much to be learned about the polymorphisms reviewed here. The SLC6A3 3′-UTR VNTR is particularly illustrative of this, since it has been associated with many phenotypes in quite a number of studies, yet the results appear inconsistent or even contradictory. Resolving these apparent inconsistencies across studies is an urgent goal to better understand the function of the 3′-UTR VNTR and its relation to drug response.
