Table 2.
Timing of Substance Use Onset Across Assessment Waves
| Alcohol | Tobacco | Marijuana | Dual Onset* | |
|---|---|---|---|---|
| At or before Fall 9th grade, N(%) | 864(25%) | 348(10%) | 503(15%) | 484(14%) |
| Spring 9th Grade, N(%) | 327(10%) | 162(5%) | 226(7%) | 127(4%) |
| Fall 10th Grade, N(%) | 241(7%) | 109(3%) | 154(5%) | 74(2%) |
| Spring 10th Grade, N(%) | 180(5%) | 88(3%) | 179(5%) | 58(2%) |
| Fall 11th Grade, N(%) | 123(4%) | 72(2%) | 125(4%) | 37(1%) |
| Spring 11th Grade, N(%) | 506(15%) | 350(10%) | 563(17%) | 405(12%) |
| Fall 12th Grade, N(%) | 180(5%) | 130(4%) | 183(5%) | 83(2%) |
| Spring 12th Grade, N(%) | 123(4%) | 100(3%) | 150(4%) | 57(2%) |
| No Initiation (or no dual initiation), N(%) | 841(25%) | 2026(60%) | 1302(39%) | 2060(61%) |
Notes. %= Percentage of participants who initiated or did not initiate substance use during each wave of assessment (percentages may not add to 100% due to rounding).
*
Percentages for dual onset represent a participant having endorsed the initiation of at least two substances during an assessment wave.