Long-term cannabis smoking is not associated with elevated cancer risk. This is according to the most scientifically valid studies in melanoma, lung, prostate, breast and cervical cancer. Scientists hypothesise the anti-oxidant properties of cannabis might override any cancer-causing chemicals found in cannabis smoke, thus 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 found moderate cannabis smoking (over a 20-year period) was associated with a reduced risk of head and neck cancer. Some cannabinoids, including THC and CBD, have been found to promote tumour cell death. These and other cannabinoids show potential as effective tools in treating cancer.
Even after years of frequent use, cannabis smoking is not associated with any permanent lung harms, such as chronic obstructive pulmonary disorder (COPD), emphysema or reduced lung function. In 2014, according to data in the International Journal of Cancer, subjects who regularly inhaled cannabis smoke possessed no greater risk of contracting lung cancer than those who consumed it occasionally, or not at all.