In an interview with the McClatchy newspaper chain, Donald Tashkin of the UCLA David Geffen School of Medicine, Division of Pulmonary and Critical Care Medicine, said: "[A]t this point, I'd be in favor of (marijuana) legalization. I wouldn't encourage anybody to smoke any substances. But I don't think it should be stigmatized as an illegal substance. Tobacco smoking causes far more harm. And in terms of an intoxicant, alcohol causes far more harm (than marijuana)."
Tashkin said that when he began his work thirty years ago, he "opposed ... legalization because [he] thought it would lead to increased use and that would lead to increased health effects." However, he now admits that his decades' worth of scientific research revealed an opposite conclusion.
In 2006, Tashkin led the largest population case-control study ever to assess the use of marijuana and lung cancer risk. The study, which included more than 2,200 subjects (1,212 cases and 1,040 controls), reported that marijuana smoking was not positively associated with cancers of the lung or upper aerodigestive tract – even among individuals who reported smoking more than 22,000 joints during their lifetime.
"What we found instead was no association and even a suggestion of some protective effect," Tashkin told the newspaper chain, noting that cannabinoids cause "cells [to] die ... before they age enough to develop mutations that might lead to cancer."