US Marijuana Use Has More Than Doubled in a Decade

Marijuana use in the United States more than doubled from 2001 to 2013, according to new research. Moreover, as more people began using marijuana, the number of people with the mental health condition that researchers call "marijuana use disorder" also increased, to about 3 percent of U.S. adults, the researchers found. The uptick in marijuana use coincides with a profusion of increasingly permissive marijuana laws.