Table 1.

Characteristics of the study population (n=73238)

Variables	Problematic Internet users after adjustment*, %	Usual Internet users after adjustment†, %	p-value
Sex			<0.001
Male	69.63	49.65
Female	30.37	50.35
Grade			<0.001
Middle school 1st	12.86	17.06
Middle school 2nd	16.95	16.56
Middle school 3rd	18.80	16.80
High school 1st	18.39	16.56
High school 2nd	16.43	16.52
High school 3rd	16.55	16.51
Residential type			<0.001
With family	94.43	95.73
With a relative	2.24	1.18
With a friend/dormitory/alone	2.22	2.56
Facility	1.12	0.53
Alcohol use			<0.001
No	40.42	46.12
Yes	59.58	53.88
Smoking			<0.001
No	65.35	75.60
Yes	34.65	24.40
Substance use			<0.001
No	98.27	99.49
Yes	1.73	0.51
Perceived stress			<0.001
Very little to little	9.62	16.76
Average	35.23	41.51
Much to very much	55.15	41.73

^*sample size=11644, weighted=614492,

^†sample size=61594, weighted=3302749