To investigate whether the way the CAGE was dichotomized affected the results, correlations based on the dichotomous CAGE were compared to those based on the CAGE with three response categories: 0, 1, and 2+ yes answers. The polychoric correlations for the CAGE with three response categories were estimated for the age groups 18–20, 21–23, 24–26, 27–29 and 30–32 cross-sectionally, using Mx. For the 15–17 year olds the number of 2+ yes answers was too low to estimate polychoric correlations. In the analyses described above on a few occasions empty cells were observed (0.7–1.7%). These were replaced by 1 to be able to run the model estimation.
