Common SNPs do not explain all of the heritability of many human phenotypes. Other genetic polymorphisms, such as rare variants or copy number variations (CNVs), likely account for some of this “missing heritability”. GWAS of CNVs in OUD found three variants to be associated with opioid dependence in a meta-analysis of African-American (case n = 547, control n = 2944) and European-American (case n = 1054, control n = 607) samples [42*]. The findings included intergenic deletions on 18q12.3 and Xq28, and a duplication on 1q21.3 encompassing the LCE3B and LCE3C genes.
