BACKGROUND AND AIMS:

Epidemiological trends show marijuana use in the U.S. to have increased in recent years. Previous research has identified cohort effects as contributing to the rising prevalence, in particular birth cohorts born after 1945. However, given recent policy efforts to regulate marijuana use at the state level, period effects could also play a contributing role. This study aims to examine whether cohort or period effects play a larger role in explaining trends in marijuana use.

DESIGN:

Using data from seven National Alcohol Surveys, we estimate age-period cohort decomposition models for marijuana use controlling for socio-demographic measures.

SETTING:

United States PARTICIPANTS: U.S. general population ages 18 and older from 1984 to 2015.

MEASUREMENTS:

Any past year marijuana use FINDINGS: Results indicate that period effects are the main driver of rising marijuana use prevalence. Models including indicators of medical and recreational marijuana policies do not find any significant positive impacts.

CONCLUSIONS:

The steep rise in marijuana use in the United States since 2005 occurred across the population and is attributable to general period effects not specifically linked to the liberalization of marijuana policies in some states.

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