Melatonin and cancer
Hmm... 'Melatonin prevents and delays chemical carcinogenisis and cancer growth in vivo in the mouse and rat. Blind people have robust, albeit mostly free-running melatonin circadian rhythms and they are at lower risk for the development of many, if not all, cancers. Women with breast cancer and men with prostate cancer have diminished nighttime melatonin secretion.' http://link.springer.com/chapter/10.1007/978-3-642-59512-7_27