Subsequent binary analyses of DSM-IIIR and DSM-IV alcohol dependence (AD3r, AD4) diagnoses were run in DZ families to permit within-family tests of association to be performed. The purpose of these analyses was to be able to directly compare our findings with those of other groups who only analysed the dichotomous diagnoses of AD. The number of affected (case) individuals in the entire sample is as follows: AD3r (959 cases) and AD4 (421). Within DZ families only, however, the number was reduced to 540 (AD3r) and 224 (AD4) cases; we did not observe significant association between either binary measure and the five SNPs of interest previously identified. Similarly, we did not observe any association with AD3r or AD4 in our MZ sample of unrelated cases and controls.
