“Cannabis use only was associated with a 45 percent reduction in bladder cancer incidence, and tobacco use only was associated with a 52 percent increase in bladder cancer,” said study author Dr. Anil A. Thomas, a fellow in urology at Kaiser Permanente Medical Center in Los Angeles…
“The theory is that there are receptors in the bladder that are affected by cannabis,” he said.
The cannabinoids [compounds] in the marijuana may link with the cannabinoid receptors in the bladder and somehow protect against cell changes that can lead to cancer..”
“…using tobacco only was associated with an increased risk of bladder cancer, whereas cannabis use only was associated with a 45% reduction in bladder cancer… cannabis use may be inversely associated with bladder cancer risk…” http://www.ncbi.nlm.nih.gov/pubmed/25623697