Importantly, rates of substance use in the Spit for Science project map onto other large studies of college-age populations. We assessed the representativeness of our sample in terms of substance use by comparing rates of substance use for the fall data collection in the Spit for Science sample with rates of substance use reported in Monitoring the Future (MTF) in their post 12th grade assessment (Johnston et al., 2010). Rates of substance use are very similar between the samples: in Spit for Science 72% of participants reporting having tried alcohol, compared to 71% in MTF. The prevalence of having tried cigarettes was 38% in Spit for Science and 42% in MTF; marijuana: 41% in Spit for Science and 44% in MTF; stimulants: 11% in both samples; sedatives: 6% in Spit for Science and 8% in MTF, and cocaine: 4% in Spit for Science and 5% in MTF. Data from another large survey of college students, The College Alcohol Study (Knight et al., 2002), conducted by the Harvard School of Public Health with data on 23,751 students from 119 4 years
