By Robert Preidt
The spike in pot use may be due to an increase in the number of people who said they use the drug on a daily or near-daily basis, said the researchers, whose study covered drug trends from 2000 to 2010.
Americans spent $100 billion a year on cocaine, heroin, marijuana and methamphetamine -- or a total of $1 trillion over the decade, the RAND Drug Policy Research Center report estimated.
"Having credible estimates of the number of heavy drug users and how much they spend is critical for evaluating policies, making decisions about treatment funding and understanding the drug revenues going to criminal organizations," study lead author Beau Kilmer, co-director of the RAND Drug Policy Research Center, said in a RAND news release.
While the overall amount spent per year on drugs remained the same from 2000 to 2010, spending patterns for certain drugs shifted. Much more was spent on cocaine than on marijuana in 2000, but that had reversed by 2010.
Because the report did not examine trends after 2010, it doesn't include recent reported increases in heroin use, or the effects of marijuana legalization in Colorado and Washington. The report also didn't look at the reasons behind changes in drug use and did not assess the effectiveness of drug-control strategies.
The report was prepared for the White House Office of National Drug Control Policy and appears on its website.