Although addiction is clinically diagnosed using the DSM, genetic research has relied on additional assessment strategies that can yield higher heritability and reduce measurement heterogeneity. For instance, nicotine dependence can be diagnosed using the DSM but, for research purposes, quantitative indices (which can also be used to define affecteds and unaffecteds) such as the Heaviness of Smoking Index107 and the Fagerstrom Test for Nicotine Dependence (FTND)108 are frequently used. Interestingly, the overlap between FTND and DSM-diagnosed individuals is modest (kappa≈0.3)109 and one study found FTND-based nicotine dependence to be more heritable than DSM-based nicotine dependence.8
