The chart below shows both the actual number of patients holding identification cards in the states (and District of Columbia) with mandatory registration, and the estimated number of patients for the states with voluntary or no registration, according to the Marijuana Policy Project.
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.
State population numbers are estimates from the US Census Bureau's 2011 data. Patient numbers were last updated in December 2012.
1. California has voluntary registration (as opposed to mandatory registration in all other legal medical marijuana states besides Washington). The Marijuana Policy Project estimated the number of California patients based on Oregon's patients per capita.
2. Connecticut's medical marijuana registration program started on Oct. 1, 2012, so data are not available yet.
3. DC's medical marijuana law took effect on July 27, 2010, but, as of Dec. 28, 2012, its registration program does not yet exist.
4. Maine did not have a registration program until Dec. 31, 2010, when it began requiring patient ID cards. As of Jan. 4, 2011, no statistics are available for the number of registered patients. The Marijuana Policy Project estimated the number of Maine patients based on Michigan's patients per capita.
5. Massachusett's medical marijuana program goes into effect on Jan. 1, 2013, and patient data is not yet available.
6. Washington does not have a registration program. The Marijuana Policy Project estimated the number of Washington patients based on Oregon's patients per capita.
7. Two states (NJ, DE) have registration programs that took effect in late 2012 which is partially why the number of registered patients in those states is comparatively low. Since our national projections are based on the average of the 16 states with active registration programs, these two states lower the average and thus lower the overall projection of medical marijuana patients
8. 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 311,591,917 as of 2011, according to the US Census Bureau), then the total number of medical marijuana users as of Dec. 28, 2012 would theoretically be 2,421,069 [7.77/1,000 x 311,591,917 = 2,421,069].
[Editor’s Note: As of Dec. 28, 2012 we were unable to find any studies projecting the number of medical marijuana users nationwide. Our national estimate of 2,421,069 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. Although Mr. Dang's statement is based on our 2009 patient estimate of 577,712, the method we used in 2012 to estimate patients is the same.]
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.]
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."
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."