Trends in Marijuana Use

Do Attitudes Toward Legalization Predict Marijuana Use?

Since the mid-1970s, there has been a close relationship between historical trends in support for legalization or decriminalization of marijuana use and historical trends in use of marijuana among high-school seniors. The following time-series graph shows data from Monitoring the Future (MTF, Johnston et al., 1975-2004) on high school seniors' attitudes toward legalization (including decriminalization) and 30-day prevalence of marijuana use. In addition, the graph shows data on attitudes toward legalization of marijuana from annual surveys of college freshmen conducted since the late 1960s by the Cooperative Institutional Research Program (CIRP) at UCLA (Astin et al., 1968-2004).

Based on this graph, how would you characterize the relationship over time between atttitudes toward marijuana legalization among college freshmen (shown in blue) and similar attitudes among high school seniors (shown in red)? How do changes in college and high school attitudes relate to changes in the monthly prevalence of marijuana use among high school seniors (shown as gray bars)? Although the Monitoring the Future project did not collect national data on marijuana use prior to 1975, what do the CIRP attitude data from 1968 to 1974 suggest about trends in marijuana use during that early period? Finally, what do these data suggest about future trends in marijuana use among high school seniors?