Heritability was estimated using the polygenic option in SOLAR (Almasy and Blangero, 1998) for the following phenotypes: DSM-IV AD, each individual DSM-IV criterion, the three continuous phenotypes based on the LCA probabilities, and membership in each latent class. Sex and birth cohort, defined by year of birth (<1930<1930-1949-1950-1969, and ≥1970), were used as covariates for all heritability calculations to account for secular trends (Grucza et al., 2008) in alcohol use and dependence.
