standardized (~age 25) and differs in this sense from the wide age range covered in the VATSPSUD sample. The VATSPSUD alcohol section began by asking about any lifetime alcohol use. In our FF4, MM1, and MM2 interviews, 8.0, 5.0, and 4.3% of participants, respectively, denied any lifetime alcohol use and were excluded from all subsequent analyses. After excluding abstainers, the total sample size on which we had data for AC and alcohol dependence was 5,073 and consisted of 1,766 complete pairs and 893 twins whose co-twins did not participate. By zygosity, the numbers of complete pairs were MZ male twins 613, DZ male 435, MZ female 440, and DZ female 278.
