Table 1.
Participant Characteristics
| Visit | T1 |
T2 |
T3 |
T4 |
T5 |
|---|---|---|---|---|---|
| n=401 | n=391 | n=383 | n=381 | n=387 | |
| Age | 15.4 (0.7) | 16.0 (0.8) | 16.4 (0.7) | 16.9 (.8) | 17.4 (0.8) |
| Years of education | 9.1 (0.8) | 9.7 (0.9) | 10.1 (0.9) | 10.7 (0.9) | 11.1 (0.8) |
| Years of education (mother) | 14.2 (2.5) | — | — | — | — |
| WRAT-4 reading standard score | 108.3 (14.7) | — | — | — | — |
| Race/ethnicity (%) | |||||
| Hispanic/Latino | 89.8 | — | — | — | — |
| Caucasian | 76.8 | — | — | — | — |
| African-American/Black | 7.7 | — | — | — | — |
| More than one race | 12.0 | — | — | — | — |
| Other/unknown | 3.4 | — | — | — | — |
| Male (%) | 54.1 | — | — | — | — |
| BMI raw score | 23.6 (4.7) | — | 24.5 (4.9) | — | 24.8 (5.5) |
| Ever used cannabis (%) | 78.6 | 79.5 | 80.4 | 80.7 | 81.9 |
| Ever used alcohol (%) | 82.0 | 86.7 | 90.2 | 92.4 | 94.2 |
| Ever used nicotine (%) | 40.6 | 44.8 | 52.1 | 55.4 | 63.8 |
| Ever used other drugs (%) | 36.2 | 40.4 | 47.6 | 49.2 | 52.6 |
| Frequency of substance use (days in past 6 months) | |||||
| Cannabis use, median (IQR) | 6.0 [0.0, 30.0] | 8.0 [8.0, 49.0] | 10.0 [0.0, 73.0] | 7.0 [0.0, 84.5] | 14.0 [0.0, 105.0] |
| Alcohol use, median (IQR) | 1.0 [0.0, 5.0] | 2.0 [0.0, 8.0] | 3.0 [1.0, 9.0] | 3.0 [0.0, 11.0] | 4 [1.0, 15.0] |
| Nicotine use, median (IQR) | 0.0 [0.0, 1.0] | 0 [0.0, 0.0] | 0.0 [0.0, 1.0] | 0.0 [0.0, 0.0] | 0.0 [0.0, 2.0] |
| Current cannabis abuse diagnosis (%) | 11.0 | 8.7 | 15.4 | 14.2 | 21.0 |
| Current cannabis dependence diagnosis (%) | 2.2 | 2.8 | 4.1 | 3.4 | 2.3 |
| Current alcohol abuse diagnosis (%) | 1.2 | 2.6 | 1.8 | 1.0 | 2.8 |
| Current alcohol dependence diagnosis (%) | 0.0 | 0.5 | 0.8 | 0.3 | 0.3 |
| Current other drug abuse diagnosis (%) | 0.2 | 0.3 | 0.8 | 0.0 | 1.5 |
| Current other drug dependence diagnosis (%) | 0.0 | 0.0 | 0.8 | 0.5 | 0.3 |
| DASS—depression subscale z-score | −0.3 (0.9) | −0.4 (0.8) | −0.3 (1.0) | −0.4 (0.8) | −0.3 (0.9) |
Note: All values are given as mean and standard deviation unless noted.
BMI, body mass index; IQR, interquartile range; T1, baseline visit; T2, 6-month follow-up visit; T3, 1-year follow-up visit; T4, 18-month follow-up visit; T5, 2-year follow-up visit; WRAT, Wide Range Achievement Test.