Table 1 shows rates of alcohol misuse measures (drinking, drunkenness, and the alcohol misuse composite) by assessment wave. As expected, alcohol misuse rates increased with age, as 7.2% and 0.9% of adolescents engaged in drinking and drunkenness, respectively, at wave 1 (M age =11.8 years), with these estimates increasing to 46.0% and 31.8%, respectively, at wave 8. Retention rates for past-month drinking and drunkenness assessments in the gPROSPER sample were high, averaging 84% across waves and ranging from 68.6% at wave 8 to 92.6% at wave 2. Logistic multilevel models predicting retention (non-missingness) in the alcohol misuse composite by wave revealed a significant decrease in retention from waves 2 to 8 (b=−0.36, SE=0.01, p<.001). Retention over time differed between control and intervention schools (intervention x wave interaction p<.001), with adolescents in control schools showing steeper decreases in retention over time (b=−0.41, SE=0.02, p<.001) compared to adolescents in intervention schools (b=−0.31, SE=0.02, p<.001).
