Table 2.
Sample Characteristics
| Variable | Nonusers | Users | Nonusers vs. Users |
|---|---|---|---|
| Age at fMRI Session, Years | |||
| Baseline | 12.77 (0.361) | 12.67 (0.322) | t40.80 = 1.16 |
| Follow-up | 15.65 (0.373) | 15.58 (0.345) | t24.21 = 0.64 |
| Gender, n | χ21 = 0.19 | ||
| Male | 29 | 12 | |
| Female | 34 | 10 | |
| WISC-IV Full Scale IQa | 103.79 (11.09) | 98.45 (13.40) | t31.63 = 1.68 |
| CBCL Externalizing Baseline t Score | 48.27 (9.41) | 51.32 (7.97) | t43.00 = −1.47 |
| CBCL Externalizing Follow-up t Score | 45.38 (9.53) | 52.68 (10.42) | t34.06 = −2.89b |
| Family Income, Dollars per Montha | 7001.63 (11,381.40) | 2996.36 (3043.25) | t78.77 = 2.53c |
| Maternal Education, Years | 14.17 (2.18) | 13.40 (1.94) | t40.87 = 1.54 |
| SES Composite, z Family Income + z Maternal Education | 0.196 (1.85) | −0.560 (1.17) | t58.68 = 2.22c |
| Race | χ21 = 4.79c | ||
| Caucasian | 39 | 7 | |
| Non-Caucasian | 24 | 15 | |
| Cannabis Age of Onset, Yearsd | - | 13.67e (1.33) | |
| Peak Cannabis Use, Maximum No. of Joints per Day (13- to 15-year-olds)d | - | 0.076 (0.161) | |
| Total Cannabis Use, Sum Joints per Day (13- to 15-year-olds)d | - | 0.078f (0.161) | |
| Any Alcohol Use (13- to 15-year-olds) | 8 | 12 | χ21 = 13.63b |
| Peak Alcohol Use, Maximum No. of Drinks per Day (13- to 15-year-olds) | 0.038 (0.055) | 0.075 (0.101) | t22.08 = −1.07 |
| Total Alcohol Use, Sum Drinks per Day (13- to 15-year-olds) | 0.040 (0.054) | 0.081 (0.101) | t22.06 = −1.17 |
| Other Illicit Drug Use, Any Use (13- to 15-year-olds) | 0 | 3 | χ21 = 5.35c |
Values are presented as mean (SD) or n.
t values determined using Welch’s unequal variance t test. χ2 values determined using Yates’s χ2 test. Peak and total alcohol use were calculated only in participants with reported alcohol use.
CBCL, Child Behavior Checklist; fMRI, functional magnetic resonance imaging; SES, socioeconomic status; WISC, Wechsler’s Intelligence Scale for Children.
Measures from the baseline visit.
p < .01.
p < .05.
Cannabis users with reported dose (n = 21); 1 participant was classified as a user based on a failed urine screen but did not report cannabis use.
Cannabis age of onset from the full user sample with reported onset (n = 21); cannabis age of onset when removing the 4 participants with inconsistent cannabis onset report was 14.20 years (SD 0.887 years).
Total cannabis use range was 0.005 to 0.6 joints per day.