RT Journal Article SR Electronic T1 Can health campaigns make people ill? The iatrogenic potential of population-based cannabis prevention JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 930 OP 931 DO 10.1136/jech.2007.060277 VO 61 IS 11 A1 Sumnall, Harry R A1 Bellis, Mark A YR 2007 UL http://jech.bmj.com/content/61/11/930.abstract AB