Why we need to be cautious about medical marijuana. Reefer sadness.

Marijuana smoke is blanketing the United States. Medical marijuana dispensaries outnumber coffee shops in some communities. And no matter where you go, there’s no escaping the debate over whether the drug should be legalized for medical or recreational purposes. Thus far, 20 states and the District of Columbia have passed laws allowing medical use of marijuana. An additional 15, including Minnesota, are considering medical marijuana legislation. Voters in Colorado and Washington recently legalized recreational marijuana use, and Oregon and Alaska may also have full legalization measures on the ballot soon. Faced with the daily barrage of marijuana chatter, I find myself rehashing the most salient issues, listening to multiple perspectives and wondering what the key tipping points will be in this historic, escalating conversation.