year follow up was equally likely in offspring of affected mothers as fathers. One limitation of the Lieb et al (2002) study was the relative infrequent occurrence of alcohol dependence in mothers (7.5%). In another population-based sample 1,514 adolescent twins were identified through Minnesota birth records and evaluated at ages 11, 14, and 17 for substance use. Having either a mother or father with a substance use disorder was reported to accelerate substance use involvement in their offspring (Walden et al., 2007). Similarly, Slutske et al. (2008) studying 1,224 male and female offspring of twins in Australia reported that having either a father or mother with alcohol dependence increased the odds (OR = 2.7, 95% CI: 1.2, 6.2) that offspring would have a history of AD. Because the sample was population-based, only 18% of the offspring had parental AD, however. One strength of the present study was that, by study design, a reasonably high proportion of the offspring were children of female alcohol dependent cases.
