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. Author manuscript; available in PMC: 2019 Mar 1.
Published in final edited form as: Drug Alcohol Depend. 2017 Dec 27;184:33–41. doi: 10.1016/j.drugalcdep.2017.11.011

Table 1.

Descriptive Statistics for Lifetime Alcohol and Marijuana Involvement by Age 17 in Three Combined Cohorts by Gender

Combined Cohorts Males Females Male: Female Effect Sizec
(N=3407–3647)a (N=1627–1747) (N=1780–1900)
Measure of Alcohol or Marijuana Involvement by Age 17 % N % N % N OR 95% CI
Ever used alcohol without parental permission 68.7 2504 70.2 1226 67.3 1278 1.14 .99, 1.32
Ever intoxicated or drunk 51.1 1786 52.2 869 50.2 917 1.10 .96, 1.25
Ever used marijuana 31.4 1145 33.5 585 29.5 560 1.20 ** 1.05, 1.38
Weekly or daily drinkingb 12.0 411 14.2 231 10.0 180 1.49 *** 1.21, 1.83
Weekly or daily marijuana useb 15.8 540 19.1 310 12.8 230 1.60 *** 1.33, 1.93
Ever consumed more than 10 drinks in 24 hoursb 26.2 905 37.1 611 16.3 294 3.03 *** 2.58, 3.55
≥ 30 lifetime uses of marijuanab 10.5 356 13.3 216 7.9 140 1.79 *** 1.43, 2.24
Mean SD Mean SD Mean SD d 95% CI
Age of alcohol initiation 14.6 2.0 14.4 2.2 14.9 1.8 .25*** .17, .33
Age of first alcohol intoxication 15.1 1.7 14.9 1.8 15.3 1.6 .25*** .16, .34
Age of marijuana initiation 15.0 1.8 14.9 1.8 15.1 1.7 .11 −.01, .22
DSM-IV Alcohol Abuse/Dependence symptom countd .51 1.3 .69 1.5 .35 1.1 .26*** .20, .33
DSM-IV Cannabis Abuse/Dependence symptom countd .45 1.5 .65 1.8 .26 1.0 .26*** .19, .32
a

Ns varied by substance phenotype from 3407 (≥ 30 lifetime uses of marijuana) to 3647 (ever used) but always exceeded 90% of baseline sample.

b

Levels of use were combined into clinically significant categories above; however, continuous or ordinal measures were used in regression models.

c

Effect sizes are expressed as odds ratios (OR) for categorical outcomes or Cohen’s d for quantitative outcomes. ORs significantly greater than 1 indicate a higher level of use for males than females (e.g., 1.49 = a 49% increase in the likelihood for males). For Cohen’s d, .20 corresponds to a small effect. Because male gender was associated with earlier initiation; males and females were reverse-coded for comparing age of initiation.

d

These raw symptom counts were log-transformed in regression analyses to mitigate positive skew.

*

p<.05,

**

p<.01,

***

p<.001.