e-cigarettes

During the 1990s and 2000s, opponents of the legalization of marijuana (be it recreational or medical) argued that it served as a "gateway" to harder drugs.

One of my extended family members is a former smoker. Nagging him to stop did little good. Warning him against its health dangers produced similarly poor results. He was addicted, and he appeared to like smoking, anyway. 

It is well documented that cigarette smoke causes lung cancer, but giving up nicotine still proves to be the most challenging part of quitting cigarettes.