[1] British Columbia Ctr Subst Use, Vancouver, BC, Canada
[2] Univ British Columbia, Dept Family Practice, Vancouver, BC, Canada
[3] Ctr Addict & Mental Hlth, Toronto, ON, Canada
[4] Univ British Columbia, St Pauls Hosp, Dept Med, Vancouver, BC, Canada
[5] Univ Waterloo, Sch Publ Hlth Sci, Waterloo, ON, Canada