Second, several early twin and adoption studies suggested that genetic factors were more important in the etiology of AUDs in men than women (Goodwin et al. 1973; Bohman et al. 1981; McGue et al. 1992) while more recent studies sometimes reached different conclusions (Heath et al. 1997; Prescott et al. 1999). Our results provide strong evidence that despite large and consistent differences in the prevalence of AUDs in the two sexes (Kessler et al. 1994; Hasin et al. 2007), genetic influences on AUD are similar in magnitude in men and women. The primary reason early twin and adoption studies were unable to detect genetic factors in AUD in females was due to very small sample sizes and relatively low prevalence rates in the female samples. When we aggregated the data across studies, the estimated heritability of AUDs was indistinguishable in the two sexes.
