Because of the skewed nature of the distributions of our AC measures, for our correlational and twin analyses, we polychotomized them into 5 categories with different cut-offs for males and females. For drink frequency, our 5 categories were 1 to 3, 4 to 9, 10 to 15, 16 to 27, and 28 to 30 days per month in males and 1, 2 to 3, 4 to 7, 8 to 14, and 15 to 30 days per month in females. For regular quantity, these categories were 1 to 2, 3, 4 to 5, 6 to 9, and ≥9 drinks/day for males; and 1, 2, 3, 4, and ≥5 drinks/ day for females. For maximum quantity, these categories were 1 to 5, 6 to 9, 10 to 12, 13 to 20, and ≥21 drinks/day for males and 1, 2 to 3, 4, 5 to 6, and ≥7 drinks/day for females. For drunk frequency, using the response options listed earlier, our categories were 1 to 2, 3 to 5, 6 to 7, 8, and 9 to 11 for males and 1, 2, 3 to 4, 5 to 7, and 8 to 11 for females.
