Marijuana use doubles to 1 in 10 US adults

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The estimated prevalence of adults who used marijuana in the past year more than doubled in the US between 2001 and 2013 to 9.5%, according to research. Laws and attitudes about marijuana are changing, with 23 states having medical marijuana laws and four of these states having also legalised marijuana for recreational use.

Dr Bridget F Grant, of the National Institute on Alcohol Abuse and Alcoholism, Rockville, Maryland, and co-authors used nationally representative data on past-year prevalence rates of marijuana use, marijuana use disorder and marijuana use disorder among marijuana users in the US. Data came from the 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) and the 2012-2013 National Epidemiologic Survey on Alcohol and Related Conditions-III (NESARC-III).

The prevalence of past-year marijuana use climbed to 9.5% of adults in 2012-2013 from 4.1% in 2001-2002, with increases particularly notable among women and individuals who were black, Hispanic, living in the South, middle-aged or older, the authors report.

The prevalence of a diagnosis of a past-year marijuana use disorder (abuse or dependence) also increased to 2.9% in 2012-2013 from 1.5% in 2001-2002, which means nearly 3 of every 10 Americans who used marijuana in the past year had a diagnosis of a marijuana use disorder (approximately 6.8m Americans). Groups with notable increases included individuals ages 45 to 64 and those individuals who were black or Hispanic, with the lowest incomes or living in the South.

Among marijuana users, the prevalence of marijuana use disorder decreased to 30.6% in 2012-2013 from 35.6% in 2001-2002. Because there was no increase in the risk for marijuana use disorder found among users, in fact there was a decrease, the increase in prevalence of marijuana use disorders can be attributed to the increase in marijuana users between the two surveys, the authors note.

“In summary, while many in the US think prohibition of recreational marijuana should be ended, this study and others suggest caution and the need for public education about the potential harms in marijuana use, including the risk for addiction. As is the case with alcohol, many individuals can use marijuana without becoming addicted. However, the clear risk for marijuana use disorders among users (approximately 30%) suggests that as the number of US users grows, so will the numbers of those experiencing problems related to such use. This information is important to convey in a balanced manner to health care professionals, policy makers and the public,” the study concludes.

Abstract
Importance: Laws and attitudes toward marijuana in the United States are becoming more permissive but little is known about whether the prevalence rates of marijuana use and marijuana use disorders have changed in the 21st century.
Objective: To present nationally representative information on the past-year prevalence rates of marijuana use, marijuana use disorder, and marijuana use disorder among marijuana users in the US adult general population and whether this has changed between 2001-2002 and 2012-2013.
Design, Setting, and Participants: Face-to-face interviews conducted in surveys of 2 nationally representative samples of US adults: the National Epidemiologic Survey on Alcohol and Related Conditions (data collected April 2001-April 2002; N = 43 093) and the National Epidemiologic Survey on Alcohol and Related Conditions–III (data collected April 2012-June 2013; N = 36 309). Data were analyzed March through May 2015.
Main Outcomes and Measures: Past-year marijuana use and DSM-IV marijuana use disorder (abuse or dependence).
Results: The past-year prevalence of marijuana use was 4.1% (SE, 0.15) in 2001-2002 and 9.5% (SE, 0.27) in 2012-2013, a significant increase (P < .05). Significant increases were also found across demographic subgroups (sex, age, race/ethnicity, education, marital status, income, urban/rural, and region). The past-year prevalence of DSM-IV marijuana use disorder was 1.5% (0.08) in 2001-2002 and 2.9% (SE, 0.13) in 2012-2013 (P < .05). With few exceptions, increases in the prevalence of marijuana use disorder between 2001-2002 and 2012-2013 were also statistically significant (P < .05) across demographic subgroups. However, the prevalence of marijuana use disorder among marijuana users decreased significantly from 2001-2002 (35.6%; SE, 1.37) to 2012-2013 (30.6%; SE, 1.04).
Conclusions and Relevance: The prevalence of marijuana use more than doubled between 2001-2002 and 2012-2013, and there was a large increase in marijuana use disorders during that time. While not all marijuana users experience problems, nearly 3 of 10 marijuana users manifested a marijuana use disorder in 2012-2013. Because the risk for marijuana use disorder did not increase among users, the increase in prevalence of marijuana use disorder is owing to an increase in prevalence of users in the US adult population. Given changing laws and attitudes toward marijuana, a balanced presentation of the likelihood of adverse consequences of marijuana use to policy makers, professionals, and the public is needed.

JAMA material
JAMA Psychiatry abstract


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