Twice as stoney

The number of Americans who use marijuana doubled in a decade, according to survey data collected from 80,000 adults by the National Institute on Alcohol Abuse and Alcoholism in 2001-02 and 2012-13. Respondents were asked whether they'd used marijuana in the past year, and whether they had signs of problematic use, such as trying but being unable to quit using weed heavily despite harm to health, or causing depression or anxiety. The most recent survey indicates that 22 million Americans, or 10 percent of the total population, now uses pot. And about 1 in 3 users—or 6.8 million people—showed signs of dependence or abuse. Use increased across all age groups, but was most common among people ages 18 to 29. The researchers attributed the increase in smoking to a cultural shift regarding recreational use.