New Zealand researchers have found that smoking a single marijuana joint is as carcinogenic to the lungs as 20 cigarettes. They reported this in the European Respiratory Journal. Regular indulgence (one joint a day for 10 years) had a 5.7 times higher lung cancer risk than nonsmokers. The findings are not surprising; smoke from cannabis contains more carcinogens and is inhaled more deeply than cigarette smoke. However, there is bound to be some dispute about the findings - the medical marijuana lobby is strong and usually able to find protagonists who strongly deny that the weed causes cancer.