Did you know that marijuana use among U.S. teens has dropped dramatically since the late 1990s? So...if you were thinking everyone smokes pot, they don't. Statistics show that about 15 percent, or roughly 1 in 7 teens, report past-month marijuana use. In the last few years, however, the decline in marijuana use has stalled, and the reason may be that fewer of you consider marijuana to be a harmful drug.BUT...that perception is not correct. In 2009,...