In summary, our analyses are consistent across 2 independent twin samples in finding fairly high genetic correlations across current AC measures and alcohol problems. This is true across several different indices of consumption (frequency of drinking, quantity of alcohol use, frequency of heavy drinking/drunkenness) and using different measures of alcohol-related problems (Mm-MAST, RAPI, DSM-IV symptom counts). Frequency of drinking appears to be the least genetically correlated with other measures of alcohol (less so than quantity of alcohol use/frequency of heavy drinking or drunkenness), suggesting there is more unique environmental variance on this aspect of alcohol use. This suggests that this measure may be least likely to “replicate” genetic effects identified with alcohol dependence. Both samples indicate that there is not a single genetic factor responsible for the phenotypic overlap between different measures of consumption and problem use. Accordingly, combining studies using different indices of alcohol use and problems may help increase power to identify shared genetic influences, but may introduce noise if the gene under study is more specific to a particular aspect of AC. Creating multivariate genetic factor scores
