themselves were interviewed via telephone in 1996–2000, after informed consent was obtained from all participants, as approved by the Institutional Review Boards of the Washington University in St. Louis, USA and the Queensland Institute of Medical Research, Australia,. Further details regarding sample ascertainment and data collection are presented in related publications (Heath et al., 2001; Knopik et al., 2004; Lynskey et al., 2003; Nelson et al., 2002).
