Table 1.
Participant Characteristics
| Initiation Group (n = 18) |
Comparison Group (n = 16) |
Statistic | Significance | |
|---|---|---|---|---|
| % Female | 38.9% | 12.5% | — | p = .125a |
| Age at fMRI Scan | 10.7 (1.2) | 10.2 (1.1) | t(32) = 1.26 | p = .216b |
| Age at First Substance Use | 13.4 (1.5) | n/a | — | — |
| Full-Scale IQ* | 106.8 (15.0) | 107.3 (12.4) | t(31) = 0.11 | p = .910b |
| Phenotypic Variables | ||||
| Family History of SUD (n; 0/1/2 parents) | 2/5/11 | 4/7/5 | — | p = .233a |
| Early Externalizing Behaviors** | 51.1 (10.2) | 46.0 (10.3) | t(32) = 1.46 | p = .155b |
| Nucleus Accumbens Variables | ||||
| Large Gain Anticipation vs. Neutral Anticipation | 1.26 (0.78) | 0.87 (0.83) | t(32) = 1.40 | p = .170 |
| Large Loss Anticipation vs. Neutral Anticipation | 0.17 (0.60) | 0.41 (0.67) | t(32) = 1.11 | p = .274 |
| Substance Use at Most Recent Follow-up | ||||
| Used Alcohol (n) | 17 | 0 | — | p < .001c |
| Used Cannabis (n) | 15 | 0 | — | p < .001c |
| Used Nicotine (n) | 8 | 0 | — | p = .003c |
| Used Other Drugs (n) | 12 | 0 | — | p = .020c |
| Used Multiple Substances (n) | 17 | 0 | — | p < .001c |
| Alcoholic Drinks Per Year*** | 75.90 (78.66) | 0 | t(17) = 3.88 | p < .001d |
| Occasions of Cannabis Use Per Year*** | 47.90 (86.70) | 0 | t(17) = 2.10 | p = .026d |
| Days of Nicotine Use Per Year*** | 136.74 (134.24) | 0 | t(16) = 2.34 | p = .016d |
| Number of Other Drugs Used Per Year*** | 1.24 (0.39) | 0 | t(17) = 5.16 | p < .001d |
| Lifetime Diagnosis (n; present/absent)**** | ||||
| Conduct Disorder | 2/15 | 0/15 | — | p = .486a |
| ADHD | 2/15 | 3/12 | — | p = .645a |
| Generalized Anxiety Disorder | 1/16 | 0/15 | — | p > .999a |
| Depressive Disorder | 2/15 | 0/15 | — | p = .486a |
Note. fMRI, functional magnetic resonance imaging; SUD, substance use disorder; ADHD, attention deficit hyperactivity disorder. Numbers represent means, with standard deviations in parentheses, unless otherwise noted.
Two-tailed Fisher’s exact test.
Two-tailed independent samples t-test.
One-tailed Fisher’s exact test.
One-tailed independent samples t-test. Degrees of freedom reduction reflects equal variances not assumed.
One participant in the initiation group was missing an IQ score.
Early externalizing data are T-scores from the Child Behavior Checklist – Parent Report.
Calculated only for those who reported using the indicated substance, beginning with the age of initiation of that substance.
One participant in each group was missing diagnostic information.