[1] Univ Newcastle, Sch Med & Publ Hlth, Ctr Clin Epidemiol & Biostat, Callaghan, NSW 2308, Australia
[2] Univ Otago, Injury Prevent Res Unit, Dunedin, New Zealand
[3] Swinburne Univ Technol, Fac Life & Social Sci, Melbourne, Vic, Australia
[4] Univ Sydney, Discipline Psychiat, Sydney, NSW 2006, Australia
[5] Univ Sydney, Discipline Addict Med, Sydney, NSW 2006, Australia
[6] Australian Natl Univ, Mental Hlth Res Ctr, Canberra, ACT, Australia
[7] Ctr Addict & Mental Hlth, Toronto, ON, Canada
[8] Amherst Coll, Dept Math, Amherst, MA 01002 USA
[9] London Sch Hyg & Trop Med, Fac Publ Hlth & Policy, London WC1, England