The Australian study differed in important respects from the studies conducted by Schuckit. First, the Australian study did not attempt to recruit people with positive family histories of alcoholism. Second, the study did not use the exclusionary criteria considered standard in contemporary research (e.g., people with histories of alcohol problems at baseline were not excluded). As a consequence of this (and probably unique for this type of research), people with and without family histories of alcoholism and people who were light or heavy drinkers, or who had problems with alcohol, participated in this study in approximately the same proportions as would be observed for the general population of Australians of this age group (Heath et al. 1999). In other words, participants (at least the men) broadly represented all twins of their age group from the Australian twin panel, showing few significant differences from those twins who did not participate. Twins who participated in the original 1981 Australian twin study who could be located also were included in the 1992 diagnostic interview followup survey. Similar to the research conducted by Schuckit,
