[1] RTI Int, Behav Epidemiol, 3040 East Cornwallis Rd, Res Triangle Pk, NC 27709 USA
[2] Lund Univ, Div Psychiat, Malmo, Sweden
[3] Univ Valencia, Univ Hosp, Valencia, Spain
[4] Univ Med Ctr Hamburg Eppendorf Martinistr, Ctr Interdisciplinary Addict Res, Hamburg, Germany
[5] RTI Int, Stat Sci, Washington, DC USA
[6] Shire, Lexington, MA USA
[7] Lund Univ, Fac Med, Dept Clin Sci Lund, Lund, Sweden