The largest study ever conducted on marijuana’s relevance to lung cancer has come up with some somewhat surprising results. The National Institutes of Health’s National Institute on Drug Abuse funded the University of California at Los Angeles study, which found that smoking marijuana does not cause lung cancer, and it doesn’t seem to matter how much or how often it is smoked.

Donald Tashkin, a pulmonologist at UCLA, has studied marijuana for 30 years. Furthermore, Tashkin’s work has previously established a tenuous link between marijuana smoking and negative health effects. For example, he found that marijuana tar contained higher concentrations of cancer-causing substances, and because of that and the fact that marijuana smokers hold smoke deep in their lungs for an extended period of time, it previously seemed likely that the health effects of prolonged exposure would become increasingly damaging:

Earlier work established that marijuana does contain cancer-causing chemicals as potentially harmful as those in tobacco, he said. However, marijuana also contains the chemical THC, which he said may kill aging cells and keep them from becoming cancerous. They were all asked about their lifetime use of marijuana, tobacco and alcohol. The heaviest marijuana smokers had lighted up more than 22,000 times, while moderately heavy usage was defined as smoking 11,000 to 22,000 marijuana cigarettes. Tashkin found that even the very heavy marijuana smokers showed no increased incidence of the three cancers studied. “This is the largest case-control study ever done, and everyone had to fill out a very extensive questionnaire about marijuana use,” he said. “Bias can creep into any research, but we controlled for as many confounding factors as we could, and so I believe these results have real meaning.” (The Washington Post)

Tashkin’s previous work, establishing possible negative effects of marijuana, has been cited quite often by health and government officials. Now that a more complete, longer study has been published demonstrating the virtual lack of expected negative side effects from marijuana smoking, will that talking point disappear? It’s hard to argue with a person that debunked themselves — you know they’re being honest about their results when not only are the results unexpected, but they ultimately refute any speculative conclusion based from previous studies of your own.

On another note, the possibility of cancer is one talking point the vape (vaporizer) community uses to promote their favored marijuana usage method. Even regular smokers will be somewhat surprised by these results.