Table 1.

Descriptive statistics of the independent, dependent, mediating and controlling variables (n = 3,975)

Dependent variable
E-cigarette use in past 30 days in Wave 5 (0 ~ 30, Mean ± SD)	1.75 ± 5.97
Independent variable
Social Media Usage Wave 3 (1 ~ 7, Mean ± SD)	5.91 ± 1.62
Mediating variable
Internalizing Problems in Wave 4 (0 ~ 4, Mean ± SD)	1.91 ± 1.62
Moderating variable
Academic Performance in Wave 4 (1 ~ 9, Mean ± SD)	7.36 ± 1.67
Covariates
Age in Wave 3 (n. %)
12–14	3,882 (97.7)
15–17	93 (2.3)
Gender in Wave 3 (n. %)
Female	2.048 (51.5)
Male	1,914 (48.2)
Race in Wave 3 ((n. %)
White alone	2,470 (62.1)
African American alone	644 (16.2)
Other	625 (15.7)
Household income in Wave 3 (n. %)
Less than $10,000	312 (7.8)
$10,000 to $24,999	670 (16.9)
$25,000 to $49,999	913 (23.0)
$50,000 to $99,999	907 (22.8)
$100,000 or more	933 (23.5)
Self-perceived physical health in Wave 3 (1 ~ 5, Mean ± SD)	4.14 ± 0.93
Self-perceived mental health in Wave 3 (1 ~ 5, Mean ± SD)	3.72 ± 1.18
Exposed to Family secondhand smoke in Wave 3 (n. %)
Yes	1,307 (32.9)
No	2,593 (65.2)
Internalizing Problems in Wave 3 (0 ~ 4, Mean ± SD)	1.76 ± 1.56
E-cigarette use in past 30 days in Wave 3 (0 ~ 30, Mean ± SD)	0.09 ± 1.11
E-cigarette use in past 30 days in Wave 4 (0 ~ 30, Mean ± SD)	0.15 ± 1.48

Notes: a SD stands for standard deviation.