The number of people using marijuana has more than doubled since 2001, according to a report published Wednesday in JAMA Psychiatry, which found the number of people reporting addiction or abuse of pot nearly doubled as well. The study—based on National Epidemiologic Survey on Alcohol and Related Conditions interviews with approximately 40,000 people in 2001 and 2013—found the number of marijuana users went from 4.1% to 9.5%, and the number of people reporting problems with marijuana use went from 1.5% to 2.9%. "While many in the United States think prohibition of recreational marijuana should be ended, this study and others suggest caution and the need for public education about the potential harms in marijuana use, including the risk for addiction," the report states.
The Oregonian reports the study found that 30% of marijuana users found themselves abusing or dependent on the drug. According to the Washington Post, that's defined as continuing to use pot despite trouble with family and friends, trying and failing to cut back on pot use, repeatedly driving while high, and more. Psychiatry professor Deborah Hasin, who led the study, says she doesn't know the reason for the increase in use and abuse. "You can speculate that Americans are increasingly viewing marijuana as a harmless substance ... or laws are changing," she says. The report's findings contradict a National Survey on Drug Use and Health study that found marijuana use only increased 12% from 2002 to 2012 and that marijuana abuse and addiction actually decreased over that time. (Read more marijuana stories.)