Recent weeks have seen a rash of new studies of marijuana hitting the mass media, generating scary headlines like "Smoking Pot Rots Your Gums," "Cannabis Bigger Cancer Risk Than Cigarettes" and "Pot Withdrawal Similar to Quitting Cigarettes. Most of this coverage can be boiled down to a fairly simple equation:
Flawed science + uncritical reporting = misinformation.
Mercifully, the U.S. mass media were so distracted by Super Tuesday, Heath Ledger's autopsy and the latest Britney Spears trauma that reports of these studies didn't get as much play as they might have. That's good, because the research had significant gaps, and the reporting ranged from slapdash to flat wretched.
Lung cancer: One joint = 20 cigarettes?
The lung cancer study was the scariest. Since cigarettes are a known lung cancer risk, it seems plausible that marijuana might carry similar risks. In fact, most of the scientific evidence tends in the opposite direction -- though one would never know it from reading either the study or the Reuters wire story that got the heaviest circulation.
Conducted in New Zealand, this was what is called a "case-control" study, in which researchers looked at a group of patients who had lung cancer and compared them to a group without cancer -- the controls -- matched for age and other demographics. All were asked about various factors that might increase their lung cancer risk, including smoking cigarettes or marijuana. After running the data on 79 cancer cases and 324 controls through myriad equations and mathematical analyses, the researchers proclaimed that one joint packed a cancer risk roughly equal to 20 cigarettes -- an assertion that became Reuters' lead.
