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September 01, 2016

Monitoring Marijuana Use in the United StatesChallenges in an Evolving Environment

Author Affiliations
  • 1Substance Abuse and Mental Health Services Administration, Rockville, Maryland
  • 2Centers for Disease Control and Prevention, Atlanta, Georgia

Copyright 2016 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.

JAMA. Published online September 1, 2016. doi:10.1001/jama.2016.13696

In 2014, an estimated 22.2 million Americans aged 12 years or older had used marijuana in the past month.1 Under federal law, marijuana is considered an illegal Schedule I drug. However, over the last 2 decades, more than half of the states have allowed limited access to marijuana or its components, Δ9-tetrahydrocannabinol (THC) and cannabidiol, for medical reasons.2 More recently, 4 states and the District of Columbia have legalized marijuana for recreational purposes. Currently, evidence for the therapeutic benefits of marijuana are limited to treatment and improvements to certain health conditions (eg, chronic pain, spasticity, nausea).3 Recreational use of marijuana is established by patterns of individual behaviors and lifestyle choices. In either case, use of marijuana or any of its components, especially in younger populations, is associated with an increased risk of certain adverse health effects, such as problems with memory, attention, and learning, that can lead to poor school performance and reduced educational and career attainment, early-onset psychotic symptoms in those at elevated risk, addiction in some users, and altered brain development.47

In September 2016, the Substance Abuse and Mental Health Services Administration and the Centers for Disease and Control and Prevention (CDC) released an issue of the CDC’s Morbidity and Mortality Weekly Report—Surveillance Summary describing historical trends in marijuana use and related indicators among the noninstitutionalized civilian population aged 12 years or older using 2002-2014 data from the National Survey on Drug Use and Health (NSDUH).8 During the last 13 years, marijuana access (ie, perceived availability) and use (ie, past-month marijuana use) have steadily increased in the United States, particularly among people aged 26 years or older, increasing from 54.9% in 2002 to 59.2% in 2014 and from 4.0% in 2002 to 6.6% in 2014, respectively. The factors associated with the national behavior patterns of marijuana use cannot be attributed solely to the heterogeneous body of state laws and policies that vary considerably with respect to year of enactment, implementation lag time, and access stipulations. However, as state laws and policies continue to evolve, these data will be useful as a baseline to monitor changes in patterns of use and associated variables. Monitoring behavioral patterns is important given the possible increased risk of adverse health consequences due to potency changes—higher concentrations of THC (the psychoactive compound)—of the cannabis plant in the United States in the last 2 decades.9

Estimates from NSDUH data suggest that in 2014, 2.5 million persons aged 12 years or older had used marijuana for the first time within the past 12 months; this projected estimate suggests that there is an average of about 7000 new users each day (approximately 1000 more new users each day in 2014 compared with in 2002). In 2014, mean age at first use of marijuana was 19 years among persons aged 12 years or older and was 15 years among persons aged 12 to 17 years.8 During 2002-2014, the estimated prevalence of marijuana use in the past month, in the past year, and daily or almost daily increased among persons aged 18 years or older but not among those aged 12 to 17 years, while the perceived risk from smoking marijuana decreased across all age groups. Conversely, the estimated prevalence of past-year marijuana dependence decreased from 1.8% in 2002 to 1.6% in 2014 among all persons aged 12 years or older and from 16.7% in 2002 to 11.9% in 2014 among past-year marijuana users.

Overall, the perceived availability to obtain marijuana among persons aged 12 years or older increased, and acquiring marijuana by buying the drug and growing it increased vs obtaining marijuana for free and sharing the drug. The percentage of persons aged 12 years or older perceiving that the maximum legal penalty for the possession of 1 oz or less of marijuana in their state of residence is a fine and no penalty increased vs perceptions that penalties included probation, community service, possible prison sentence, and mandatory prison sentence.8 These findings on perceived availability to obtain marijuana and fewer punitive legal penalties (eg, no penalty) for the possession of marijuana for personal use may play a role in the observed increased prevalence in use among adults in the United States. However, surveillance data do not reveal causal relationships; therefore, more granular research is needed.

As states adopt policies that increase legal access to marijuana, new indicators will be needed to understand trends in marijuana use and the risk of health effects. Questions regarding mode of use (eg, smoked, vaped, dabbed, eaten, drunk), frequency of use, potency of marijuana consumed, and reasons for use (ie, medical use, recreational use, or both) could be added to existing surveillance systems or launched in new systems. Traditionally, understanding factors underlying the trends in marijuana use have been assessed by looking at 1 or 2 indicators (eg, perception of harm risk or dependence or abuse). A multivariable approach that includes environmental (eg, law enforcement, laws/policies) and cultural (eg, religion, individual choice) factors might be required to understand the relationship between the perceptions and attitudes toward marijuana and use behavior.

The health effects associated with marijuana use are still widely debated. Nonetheless, marijuana use during early stages of life, when the brain is developing, poses potential public health concerns, including reduced educational attainment, addiction in some users, poor education outcomes, altered brain structure and function, and cognitive impairment.47 Given these potential health and social consequences of marijuana use, additional data sources at the federal and state levels may be required to assess the public health effects of marijuana use. These sources may include data from sectors such as health care (eg, emergency department data), criminal justice (eg, law enforcement data), education (eg, school attendance and performance data), and transportation (eg, motor vehicle injury data). Assessing the prevalence and public health effects of marijuana use in the United States remains important given the evolving policies for marijuana for medical or recreational use at the state level. Therefore, it is vital to continue to monitor key traditional marijuana indicators but also to enhance public health surveillance to include monitoring of indicators that assess emerging issues so that public health actions could prevent adverse health consequences.

Given that legislation, types of products, use patterns, and evidence for potential harms and benefits of marijuana and its compounds are all evolving, clinicians need to understand the magnitude of marijuana use and associated behaviors so they can provide informed answers to patient questions, screen, counsel, treat, and refer patients to community treatment or counseling centers if abuse or adverse effects are identified.

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Article Information

Corresponding Author: Alejandro Azofeifa, DDS, MSc, MPH, Substance Abuse and Mental Health Services Administration, 5600 Fisher Ln, Room 15E-29D, Rockville, MD 20857 (

Published Online: September 1, 2016. doi:10.1001/jama.2016.13696

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Disclaimer: The conclusions of this article are those of the authors and do not necessarily represent the official position of the Substance Abuse and Mental Health Services Administration or the CDC.

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