No: Feb. 3, 2006 Heavy marijuana use linked to bladder cancer http://today.reuters.co.uk/news/newsArticle.aspx?type=healthNews&storyID=2006-02-03T181519Z_01_COL365758_RTRIDST_0_HEALTH-MARIJUANA-BLADDER-DC.XML&archived=False Yes: Oct. 15, 2005 Marijuana-like drug multiplies neurons http://www.sciencenews.org/articles/20051015/fob7.asp