Table 1.
Comparison of baseline (Y1) sample characteristics, by marijuana trajectory group membership.
| All (N=1,253) | Non-Use (n=766) | Low-Stable (n=154) | Early-Decline (n=81) | Late-Increase (n=74) | College-Peak (n=100) | Chronic (n=78) | |
|---|---|---|---|---|---|---|---|
| % of sample | 100.0 | 61.1 | 12.3 | 6.5 | 5.9 | 8.0 | 6.2 |
| %wt of target populationa | 100.0 | 71.5 | 10.0 | 4.3 | 4.7 | 5.4 | 4.2 |
|
| |||||||
| % Male** | 48.5 | 41.9 | 48.1 | 58.0 | 68.9 | 62.0 | 67.9 |
| % White** | 73.1 | 68.9 | 75.3 | 85.2 | 77.0 | 80.8 | 83.3 |
| % Hispanic | 4.7 | 4.8 | 6.5 | 4.9 | 4.1 | 3.1 | 2.6 |
| Mean (SD) neighborhood incomeb, * | 7.3 (3.4) | 7.1 (3.3) | 7.4 (3.3) | 7.5 (3.4) | 7.5 (3.4) | 7.5 (3.7) | 8.5 (4.1) |
| Mean (SD) Age | 18.2 (.5) | 18.2 (.5) | 18.2 (.5) | 18.2 (.5) | 18.2 (.5) | 18.2 (.5) | 18.2 (.5) |
| Mean (SD) GHQ-12 score | 9.6 (4.2) | 9.7 (4.1) | 9.8 (4.3) | 9.8 (4.8) | 9.1 (3.4) | 9.3 (4.5) | 10.0 (4.9) |
| Mean (SD) BDI score | 5.3 (5.2) | 5.4 (5.3) | 5.2 (4.8) | 5.6 (5.4) | 4.3 (4.0) | 5.0 (5.1) | 6.2 (5.9) |
| Mean (SD) BAI score | 7.6 (7.1) | 7.7 (7.2) | 7.0 (5.6) | 8.9 (8.5) | 7.2 (8.0) | 6.1 (6.7) | 8.8 (7.2) |
| % Smoked cigarettes in the past month** | 24.0 | 14.0 | 24.7 | 32.1 | 35.1 | 57.0 | 59.7 |
| % Met DSM-IV criteria for alcohol dependence** | 14.7 | 9.8 | 19.6 | 25.9 | 16.2 | 24.2 | 26.9 |
| Age at onset of marijuana use** | |||||||
| % <15 | 18.5 | 9.1 | 29.2 | 40.8 | 20.0 | 40.4 | 58.8 |
| % 15–17 | 19.2 | 12.5 | 22.5 | 44.9 | 40.0 | 40.4 | 29.4 |
| % ≥ 18 | 62.3 | 78.4 | 48.3 | 14.3 | 40.0 | 19.2 | 11.8 |
Note: GHQ-12=General Health Questionnaire. BDI=Beck Depression Inventory. BAI=Beck Anxiety Inventory.
a
Weighted percent (%wt) of target population is statistically adjusted to correct for purposive sampling design.
b
The mean adjusted gross income for each participant’s home ZIP code during their last year in high school, measured in ten thousands.
*
p<.05;
**
p<.001