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. Author manuscript; available in PMC: 2020 Jan 1.
Published in final edited form as: Drug Alcohol Depend. 2018 Nov 15;194:318–325. doi: 10.1016/j.drugalcdep.2018.11.003

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.

a

Two-tailed Fisher’s exact test.

b

Two-tailed independent samples t-test.

c

One-tailed Fisher’s exact test.

d

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.