After marijuana was legalized for adults in the U.S.
state of Washington, younger teens there perceived
it to be less harmful and reported using it more, a
new study found.
The study authors believe their research is the
first in the nation to assess changes in teens'
perceptions and marijuana use before and after
legalized recreational use, and compare these
attitudes and use in 45 other contiguous states
where marijuana use is not legal.
The data showed that legalization of recreational
marijuana use significantly reduced perceptions of
marijuana's harmfulness by 14 percent and 16 percent
among eighth and 10th graders and increased their
past-month marijuana use by 2 percent and 4 percent
in Washington state but not in Colorado.
The researchers compared data on the perceived
harmfulness of marijuana use to health and
self-reported marijuana use for nearly 254,000
students in the eighth, 10th and 12th grades in
Colorado, Washington and 45 other contiguous U.S.
states who participated in the Monitoring the Future
The survey measures drug, alcohol and cigarette use
and related attitudes among adolescent students
"While legalization for recreational purposes is
currently limited to adults, potential impacts on
adolescent marijuana use are of particular concern,"
said Magdalena Cerdá, an epidemiologist with the UC
Davis Violence Prevention Research Program and first
author of the study.
"Some adolescents who try marijuana will go on to
chronic use, with an accompanying range of adverse
outcomes, from cognitive impairment to downward
social mobility, financial, work-related and
We need to better understand the impact of
recreational marijuana use so we're better prepared
to prevent adverse consequences among the most
vulnerable sectors of the population," Cerdá said.
"The perceived harmfulness of marijuana has declined
sharply in the U.S. in the last few years, despite
the fact that there are adverse consequences
associated with marijuana use in some adults and in
adolescents," said Deborah Hasin, a professor of
epidemiology at Columbia University's Mailman School
of Public Health and in psychiatry at Columbia
University and principal investigator of the study.
"Epidemiologic monitoring of these consequences as
more states legalize recreational use, and public
education about potential health consequences, are
important to protect public health," Hasin said.
Cerdá noted that the study suggests that
legalization of marijuana in Washington reduced
stigma and perceived risk of use, which could
explain why younger adolescents are using more
marijuana after legalization.
"Other potential reasons for the increase in use
include increased access to marijuana through
third-party purchases, and lower price," Cerdá said.
"Older adolescents may also have had their attitudes
and beliefs about marijuana formed before
recreational marijuana use was legalized, making it
less likely their use would change after
For more information
Association of State Recreational Marijuana Laws
With Adolescent Marijuana Use