People who use marijuana for medical purposes are much more likely to vaporize or consume edible forms of the drug than recreational users, according to a new RAND Corporation study.
The study, which surveyed people from four western states that have legalized medical marijuana, also found that those who use marijuana for medicinal purposes are more likely to report daily or near-daily use and consume more as measured by grams per day.
In addition, those who only use marijuana for medicinal purposes do not report use of marijuana concurrently with alcohol, while those who report using recreationally consume marijuana with alcohol on nearly one in five occasions. Findings regarding the simultaneous use of alcohol and marijuana is important because past research shows such activity is more likely to result in health harm, including accidents.
The study, found that 41 percent of people reported having used marijuana recreationally at least once in their lifetime, while only about 7 percent of those surveyed reported using marijuana for medical purposes. More than half of those who said they used for medicinal purposes reported that they did not have a physician's recommendation to do so.
Published online by the journal Addiction, the study provides some of the first evidence about patterns of marijuana use in states that have legalized medical marijuana. While past efforts have surveyed special populations such as those suffering from cancer pain, the RAND study draws on a sample of the general household population in these states.
"Understanding how people use marijuana will allow us to better understand the implications of changing policies and better track changes in behavior," said Rosalie Pacula, the study's lead author and a senior economist at RAND, a nonprofit research organization. "Our findings provide new insights, but there is still much more that we need to learn."
The RAND study surveyed 1,994 people from Colorado, New Mexico, Oregon and Washington state in October of 2013 about their marijuana use, including the frequency of use and where they consumed the drug. At the time of the survey, Colorado and Washington voters had voted to legalize recreational use, but retail outlets for recreational sales had not yet opened. Survey participants were recruited from an Internet-based panel of adults and statistical weighting was used to make the group representative of the household population in each of the states.
Researchers caution that their survey included a high proportion of women and relatively few younger people, which could skew the results. However, the study's findings on several questions about overall marijuana use were similar to previous studies.
The survey found rates of lifetime use of medical marijuana were similar in Colorado and Washington (8.8 percent and 8.2 percent), while the rates were lower in Oregon (6.5 percent) and New Mexico (1 percent). Lifetime use of recreational cannabis was similar in Oregon and Washington (about 45 percent in both states), while rates were lower in Colorado (36 percent) and New Mexico (32 percent).
About 86 percent of the people who reported using marijuana for medical purposes also use the drug recreationally. Using cannabis during the past month -- a common metric for regular marijuana use -- was higher among medical marijuana users than recreational users, consistent with the notion that medical users would use the substance more regularly.
"We found that relatively few people were growing their own marijuana and many people who used medical marijuana were getting it from dealers, rather than from dispensaries," Pacula said.
The rate of simultaneous use of alcohol and marijuana was lower than researchers expected. About 17 percent of recreational marijuana users reported they usually used cannabis and alcohol together, while such use was reported by fewer than 3 percent of those who said they use marijuana for both recreational and medical purposes.
"Our sample captured a relatively small number of younger people so we need to be particularly cautious about these results on concurrent use," Pacula said. "While the results clearly indicate that the household population aged 30 and older do not commonly use these substances concurrently even for recreational purposes, we cannot presume that is the case for adolescents or young adults, whose motivations for using may differ from those captured in this study.
"But our findings suggest that public health officials concerned about the risks of simultaneous use of alcohol and cannabis should focus on people who use cannabis exclusively for recreational purposes."
People who use marijuana for both medicinal and recreational purposes were more than three times as likely to report recreational cannabis use on a near-daily basis as compared to those who use marijuana only for recreation. The same group also consumed more cannabis on average each day than recreational-only users (1.1 gram per day versus 0.35 grams) and spent more each month on cannabis ($50.50 versus $24.80).
"It will be important to watch how these self-reported behaviors change with the opening of retail outlets in legalizing states," Pacula said.
Support for the study was provided by the National Institute on Drug Abuse. Other authors of the study are Mireille Jacobson of the University of California, Irvine and Ervant J. Maksabedian of the Pardee RAND Graduate School.
Since 1989, the RAND Drug Policy Research Center has conducted research to help policymakers in the United States and throughout the world address issues involving alcohol and other drugs. In doing so, the center brings an objective and data-driven perspective to an often emotional and fractious policy arena.