The following chart shows the number of medical marijuana patients in 12 of the 13 states with legal medical marijuana laws through 2008 (Michigan's registration program is scheduled to begin on Apr. 4, 2009).
We recognize the possibility that not all medical marijuana users register for identification cards and not all of the people registered have valid medical uses for the marijuana. The chart below shows both the actual number of patients holding identification cards in the nine states with mandatory registration and the estimated number of patients (according to MPP, the Marijuana Policy Project) for the three states (CA, OR, and WA) with voluntary or no registration.
State population numbers are from the US Census Bureau's 2006 data. Unless otherwise noted, the chart reflects the information from each state's official registry website that was available as of Jan. 14, 2009.
1. California has voluntary registration (as opposed to mandatory registration in all other legal medical marijuana states besides Washington and Maine), so we used the estimate made by the Marijuana Policy Project (MPP), which is based on Oregon's per capita number of 5.55 medical marijuana patients per 1,000 state residents. The number of voluntarily registered users in California was 27,023 as of Feb. 6, 2009 according to the state's medical marijuana program website.
2. Maine does not have a registration program. 227 is an estimate by MPP based on Vermont's per capita of 0.17 medical marijuana patients per 1,000 state residents.
3. Washington does not have a registration program. 35,510 is an estimate by MPP based on Oregon's per capita number of 5.55 medical marijuana patients per 1,000 state residents.
4. If the average number of medical marijuana patients per 1,000 residents in states with legal medical marijuana is extrapolated to all 50 states (population 304,058,724 as of 2008, according to the US Census Bureau), then the total number of medical marijuana users as of Feb. 9, 2009 would theoretically be 577,712. [1.90/1,000 x 304,058,724 = 577,712].
[Editor’s Note: As of Mar. 11, 2009 we were unable to find any studies projecting the number of medical marijuana users nationwide. Our national estimate of 577,712 may not be nor is it intended to be scientifically or statistically sound. It is presented only to give a general reference point for discussion of medical marijuana use in the United States. Please see the statement below from Jeff Dang, MPH, for further critical discussion on the techniques used to create this estimate.]
Bruce Mirken, Director of Communications for the Marijuana Policy Project (MPP), wrote the following in a Nov. 18, 2008 email to ProCon.org:
"Our overall estimate of legal patients in the [twelve] medical marijuana states is 269,085... For states that don't have mandatory registries, we've estimated the number of patients based on the per capita rate a nearby state with such a registry (e.g. we used the Oregon stats to base an estimate for California). Estimates, of course, are just that and are inevitably imperfect."
Americans for Safe Access (ASA) stated the following in a Nov. 15, 2007 press release titled "Medical Marijuana Documentary Sparks Bigger Debate":
"The non-profit marijuana advocacy group Americans for Safe Access, estimates that 300,000 Americans use medical marijuana."
[Editor's Note: On Nov. 19, 2008, ProCon.org spoke with ASA spokesman Chris Hermes by phone. He explained that since registration is not required in all states with legal medical marijuana, the actual number of medical marijuana patients is unknown. He said 300,000 is ASA's best estimate.]
Dale Gieringer, PhD, State Coordinator of the California National Organization for the Reform of Marijuana Laws (NORML) wrote in his article "The Acceptance of Medicinal Marijuana in the US," published Jan. 29, 2003 in the Journal of Cannabis Therapeutics:
"Use of cannabis has become increasingly widespread due to state laws sanctioning its use. The extent of use was estimated by surveying official patient registries, private patients' groups, and physicians specializing in cannabis medicine. As of May, 2002, five states with official registration programs reported a total of over 3,400 patients, ranging from a high of 79 patients per 100,000 population in Oregon to a low of 3 per 100,000 in Colorado. California, which lacks a statewide registration system, has the highest concentration of patients, estimated at 30,000 (89 per 100,000). The rate of usage varies widely between different regions. Some 1% of the population in Mendocino County, California, are legal cannabis patients, while Canadian surveys suggest illegal usage as high as 2%-4%. As many as 5% of registered physicians have recommended marijuana in Oregon."
Jeff Dang, MPH, Substance Abuse Researcher at the UCLA School of Public Health, wrote the following in a Mar. 10, 2009 email to ProCon.org:
"ProCon.org should be congratulated for providing an estimate of the number of people who hold identification cards for medical marijuana in several states throughout the country. Furthermore, ProCon.org has provided an estimate that currently serves as a general reference point for enumerating the total number of medical marijuana patients in the country. ProCon.org has conscientiously disclosed many of the problems associated with their estimates and provided the algorithms that were used to derive the estimates (see [above] footnotes). However, two notable limitations should be added and have been delineated below.
First, the current estimate of 577,712 included data from a variety of sources (e.g. estimates from the Marijuana Policy Project and data from the Census Bureau). In several states, different data collection and estimation methods were employed. It is important to note that each approach contributes additional sources of bias and error that have not been teased apart or accounted for in the current estimate. More generally, the quality of the data have not been verified or described in detail. Secondly, it is clear that systematic probability sampling techniques were not employed therefore these numbers cannot be generalized to the rest of the nation. In other words, these particular states are not representative of all states in the US and the sample data are not representative of US population.
To derive more accurate estimates, rigorous research methods should be employed. In particular, random sampling remains the gold standard for estimating prevalence. The reality, however, is that research is often conducted on a shoestring budget and practical concerns often prevent the kind of research that is actually desired."
[Editor's Note: Although not directly related to our question about the US, we decided to include the information below about Canada for comparison.]
The Medical Marijuana Information Resource Centre stated in its online article titled "Medical Marijuana in Canada: Estimates of Medical Marijuana Use" (accessed Sep. 23, 2008):
"The exact number of medical marijuana users in Canada is not known. Estimates vary from 'tens of thousands' of Canadians to 'hundreds of thousands'. Estimates are complicated by the fact that definitions of 'medical use' of marijuana vary, ranging from those with self identified medical needs (higher estimates) to more restrictive estimates which are based on clinical indicators (lower estimates), such as those patients with Multiple Sclerosis, HIV/AIDS, Cancer, Spinal Cord Injury or Disease, Epilepsy, and Severe Arthritis.
In Canada, a general population survey that included questions about the medical use of marijuana was conducted in 2001 by researchers at the Centre for Addiction and Mental Health (CAMH), and published in the Canadian Medical Association Journal (CMAJ). This study revealed that, based on self-identified needs, an estimated 2% (or 400,000) Canadian adults may be using marijuana for medical purposes."
