This from the Drug Policy Alliance website (http://blog.drugpolicy.org/) :
Even Smoking 22,000 Joints Will Not Give You Cancer
A team of UCLA researches recently published the results of their study on the possible link between heavy marijuana use and cancer. Guess what? There is none! That's right - the researchers found no increased incidence of cancer among the over 2,200 people they observed, some of whom had consumed over 22,000 joints in their lifetime (!!). Marijuana expert and good friend, Mitch Earleywine, brought this study to my attention. His comments in an email this morning were spot on:
This is a fine study conducted by a recognized expert in the field. The sample is extremely large, and the design is powerful. Clearly, if marijuana caused lung cancer, it should appear in this study. The compelling evidence for tobacco-induced lung cancer suggests that the study is perfectly capable of revealing correlates of this disease. Surely now we can all see that the most negative consequences of cannabis are legal!Apparently, the researchers themselves were shocked [shocked I tell you] by the results. Can't you just imagine them going over the data again and again to be sure they hadn't made some mistake:
The new findings are surprising for several reasons, Dr. Tashkin said. Previous studies have shown that marijuana tar contains about 50% higher concentrations of chemicals linked to lung cancer, compared with tobacco tar, he noted. Smoking a marijuana cigarette deposits four times more tar in the lungs than smoking an equivalent amount of tobacco. "Marijuana is packed more loosely than tobacco, so thereâ€™s less filtration through the rod of the cigarette, so more particles will be inhaled," Dr. Tashkin said. "And marijuana smokers typically smoke differently than tobacco smokers - they hold their breath about four times longer, allowing more time for extra fine particles to deposit in the lung."
One possible explanation for the new findings, he said, is that THC, a chemical in marijuana smoke, may encourage aging cells to die earlier and therefore be less likely to undergo cancerous transformation.
The next step, Dr. Tashkin says, is to study the DNA samples of the subjects, to see whether there are some heavy marijuana users who may be at increased risk of developing cancer if they have a genetic susceptibility for cancer.