An open area of development in the genetic epidemiology of SUD research involves the use of multiple measures. Prior twin studies introduced the idea that multiple measures could be used to understand the characterize SUD. For example, a highly heritable nicotine dependence phenotype was estimated through the use of phenotypic and genetic factor analyses of DSM-IV ND criteria as well as the Heaviness of Smoking Index (Lessov et al., 2004). As GWAS data as well as multiple SUD measures become available, this approach can be adapted for genetic association studies. A recent genetic association study used factor analysis to determine the factor stucture across 42 tobacco use variables (e.g., cigarettes per day, nicotine dependence symptoms). Factor scores reflecting tobacco use were then derived to test for gene-based associations focusing on 231 single nucleotide variants within the CHRN and CYP genes. Suggestive associations were identified for variants in CYP2B6 near CYP2A6 (rs45482602) and CYP4Z2P (rs10749865; Richmond-Rakerd et al., 2017).
