According to the most scientifically valid studies, long-term marijuana smoking is not associated with elevated cancer risk, including lung, melanoma, prostate, breast or cervix.
Scientists hypothesize that the anti-oxidant properties of marijuana might override any cancer-causing chemicals found in marijuana smoke, therefore protecting the body against the impact of smoking. That alone is a huge surprise to most people, but that’s just the beginning.
A study in 2009 actually found that moderate marijuana smoking over a 20-year period was actually associated with reduced risk of head and neck cancer. In fact, some of the chemicals in marijuana, such as THC and especially CBD, have been found to promote tumor cell death and show potential as effective tools in treating cancer.
Marijuana smoking is not associated with any other permanent lung harms, such as chronic obstructive pulmonary disorder, emphysema or reduced lung function – even after years of frequent use.