Table 3. Associations Between Level of Exposure to Marijuana Advertisements in Recent Months and Current Marijuana Use Among US Middle and High School Students, Monitoring the Future Survey, 2014 and 2015^a .

Characteristic	Prevalence of Marijuana Useb (n = 12,988)		Frequency of Marijuana Use in Last 30 Days Among Current Users (n = 1,806)
	Adjusted ORc (95% CI)	P Value	βc (SE)	P Value
No. of exposures
0	1 [Reference]		1 [Reference]
1	1.6 (1.3–2.0)	<.001	0.07 (0.2)	.67
2	1.7 (1.4–2.1)	<.001	0.32 (0.2)	.07
3	2.1 (1.6–2.7)	<.001	0.30 (0.2)	.17
≥4	2.1 (1.7–2.6)	<.001	0.27 (0.2)	.11
Grade
8	1 [Reference]		1 [Reference]
10	3.2 (2.5–3.9)	<.001	0.01 (0.2)	.95
12	4.0 (3.2–5.0)	<.001	0.23 (0.2)	.26
Sex
Male	1 [Reference]		1 [Reference]
Female	0.9 (0.7–1.0)	.048	−0.70 (0.1)	<.001
Race/ethnicity
White	1 [Reference]		1 [Reference]
Black	1.3 (1.0–1.6)	.03	0.01 (0.2)	.97
Hispanic	1.0 (0.8–1.2)	.76	−0.31 (0.1)	.04
Parental education
<High school diploma	1 [Reference]		1 [Reference]
High school diploma	0.9 (0.7–1.2)	.45	−0.32 (0.2)	.09
College or higher	0.6 (0.5–0.8)	.001	−0.53 (0.2)	.006
Region
Northeast	1 [Reference]		1 [Reference]
North Central	0.7 (0.6–0.9)	.004	0.08 (0.2)	.66
South	0.7 (0.6–0.9)	.004	0.09 (0.2)	.57
West	0.7 (0.6–0.9)	.009	−0.32 (0.2)	.08
Population density
Large MSA	1.4 (1.1–1.7)	.004	−0.23 (0.2)	.20
Other MSA	1.2 (1.0–1.5)	.03	0.002 (0.2)	.99
Non MSA	1 [Reference]		1 [Reference]

Abbreviations: CI, confidence interval; MSA, metropolitan statistical area; OR, odds ratio; SE, standard error.

^a Data sources: Johnston et al (19–22).

^b Students who reported no current use of marijuana were the reference group.

^c Adjusted ORs and regression coefficients were adjusted for grade, sex, race/ethnicity, parental education, region, and population density in the multivariable analysis.