Source: Arria et al. [30], Source legend: Graphed lines depict the weighted cumulative percent of all students who ever had the opportunity to try a substance by each age, as of the sophomore year of college. Circles on the graph indicate the age by which 50% of all students who were ever exposed to the substance had experienced their first opportunity. The mean age at first opportunity is reported for all students who ever had the opportunity to try a substance. Amphetamines include methamphetamine, but do not include prescription or over-the-counter medications.

Figure 1: Cumulative weighted frequency of exposure opportunity to use alcohol, tobacco, and 10 other drugs, by age in years.