There was also a significant four-way interaction of the single-item CDP age of onset with medication group, genotype, and week (t = 2.26, p = 0.026). When analyzed by genotype, there was a significant three-way interaction of age of onset, medication group, and week among L′ homozygotes (t = 3.16, p = 0.007), but not S′ carriers (t = 1.03, p = 0.31). Analogous to the findings for drinking days, among L′ homozygotes, EOAs treated with sertraline reported more heavy drinking days than those receiving placebo. The converse was true for LOAs, such that the sertraline group had fewer heavy drinking days than the placebo group. All of the parameter estimates using the CDP-derived age of onset were within the standard errors of the parameter estimates obtained by Kranzler et al. (2011) using the SCID-derived age of onset.
