It is of interest to compare these findings with those of two other disorders where twin studies have been subject to similar meta-analyses. In major depression, six twin studies were examined and produced an aggregate heritability estimate of 0.37 (95% CI 0.31– 0.42) (Sullivan et al. 2000). In schizophrenia, 12 twin studies were available and the meta-analytic heritability estimate was 0.81 (95% CI 0.73–0.90) (Sullivan et al. 2003). The estimated heritability of AUDs was in between that found for major depression and schizophrenia, and outside the 95% CIs of both disorders. These results imply that the heritability of psychiatric disorders do genuinely differ from one another (Kendler, 2001).
