Twin correlations in the five sex-zygosity groups are seen in Tables 2, 3 and 4. In the same-sex pairs, the twin correlations for DA, CB and AUD were substantially higher in MZ than in DZ twins and modestly higher in same-sex than in opposite sex DZ pairs. In all twin pairs, the within-syndrome cross-twin correlations were moderately higher than the cross-syndrome cross-twin correlations. For example, in MZ females the correlations for DA, CB and AUD ranged from +.64 to +0.71 with a mean of +0.68. The cross-disorder cross twin correlations ranged from +0.38 to +0.59, with a mean of +0.47.
