As AUDIT can be rapidly ascertained in large populations, we explored methods for dichotomizing AUDIT total score that optimized the genetic correlation with DSM-IV alcohol dependence (13). Higher genetic correlations with alcohol dependence were observed as the control threshold was increased from 2 to 4, and with increasingly stringent case cut-offs (Figure 3 and Supplementary Table 2). The highest genetic correlation was observed for cases with AUDIT total score ≥20 and controls ≤4 (rg = 0.90, SE = 0.25, p = 3.0 × 10−4), however, this highly stringent threshold produced very few cases (N=1,290). The standard error of the estimate is much larger at more stringent case thresholds and therefore these estimates should be interpreted with caution. Defining cases as ≥12 yielded an rg of 0.82 (SE = 0.18, p = 3.2 × 10−6) while retaining more than 7 times as many cases (N=9,130), these genetic correlations were not significantly different from those obtained using cases ≥20 and controls ≤4 (p = 0.80).
