The National Survey on Drug Use and Health reported an estimated 22.5 million Americans 12 or older -- representing 8.7 percent of the population in that age category -- were illicit drug users in 2011.
Illicit drug use endangers public health and safety and depletes financial resources, and the scale of the problem has not improved over the past decade, the Government Accountability Office said in a letter to Sens. Dianne Feinstein, D-Calif., and Charles Grassley, R-Iowa, heads of the U.S. Senate Caucus on International Narcotics Control.
For example, the Department of Justice's National Drug Intelligence Center estimated the economic impact of illicit drug use -- including the costs of healthcare, crime and lost productivity -- was more than $193 billion in 2007.
Illicit drugs include marijuana, including hashish; cocaine, including crack; heroin; hallucinogens; inhalants; and non-medical use of prescription drugs, such as pain relievers and sedatives, the letter said.
The 2011 National Survey on Drug Use and Health: Summary of National Findings also found:
-- Marijuana was the most commonly used illicit drug, with 18.1 million saying they had used pot in the past month.
-- The rate of marijuana use increased from 5.8 percent in 2007 to 7.0 percent in 2011, and the number of users increased from 14.5 million to 18.1 million.
-- There were 1.4 million current cocaine users 12 or older in 2011, comprising 0.5 percent of the population. That was similar to the rate in 2010, 1.5 million or 0.6 percent, but lower than the estimates in 2006, 2.4 million or 1 percent.