Table 1. Socio-demographics, substance use, and internet use of Chinese university freshmen and results of multiple linear regression on the smoking-loneliness association, adjusting for socio-demographic variables, current drinking, lifetime illicit drug use, and daily hours of internet use.

Variables	Subtypes	n	Independent samples t-test				Multiple linear regression
			Loneliness score	t	P		Unstandardized coefficient	t	P
Current smoking	No	1,379	8.53±3.72				1
	Yes	73	11.90±4.60	7.351	<0.001		3.053	6.639	<0.001
Gender	Male	867	8.72±3.83				1
	Female	585	8.67±3.87	0.208	0.835		0.305	1.433	0.152
Age group (years)	≤20	860	8.67±3.84				1
	>20	592	8.74±3.85	0.35	0.727		−0.100	0.497	0.619
Ethnic group	Han	1,338	8.72±3.84				1
	Minority	114	8.49±3.90	0.602	0.548		−0.227	0.622	0.534
Place of origin	Urban	1,049	8.53±3.87				1
	Rural	403	9.15±3.74	2.772	0.006		0.405	1.622	0.105
Living arrangement	With roommates	1,417	8.67±3.83				1
	With family members	35	9.71±4.17	1.583	0.114		0.670	1.041	0.298
Self-rated family financial status	Good and moderate	1,325	8.59±3.83				1
	Poor	127	9.80±3.85	3.403	0.001		0.877	2.315	0.021
The only child	No	1,079	8.55±3.78				1
	Yes	373	9.12±3.98	2.447	0.015		0.110	0.428	0.669
Marital status of parents	Married	1,362	8.59±3.81				1
	Others*	90	10.30±3.92	4.104	<0.001		1.436	3.493	<0.001
Participating in any campus organization	Yes	1,200	8.59±3.75				1
	No	252	9.24±4.23	2.286	0.023		0.768	2.914	0.004
Current drinking	No	883	8.59±3.98				1
	Yes	569	8.87±3.61	1.376	0.169		0.122	0.581	0.561
Lifetime use of any illicit drug	No	1,441	8.69±3.84				1
	Yes	11	9.91±3.75	1.049	0.295		0.353	0.310	0.756
Daily hours of internet use	≤4	1,264	8.55±3.82				1
	>4	188	9.68±3.82	3.752	<0.001		0.895	3.046	0.002

*, “Others’’ included never-married, separated, divorced, widowed, cohabitating, and remarried.