Associations of excessive smartphone duration and unlock frequency with non-suicidal self-injury in college students

Table 2 Association between smartphone use and non-suicidal self-injury

Smartphone use	Categories	OR (95%CI)
		Model 11	Model 22	Model 33
Smartphone duration, continuous variable	Per 21 hours/week	1.17 (1.10, 1.25)	1.15 (1.08, 1.23)	1.16 (1.08, 1.24)
Smartphone duration, categorical variable	0-21 hours/week	1 (reference)	1 (reference)	1 (reference)
	21-42 hours/week	1.08 (0.76, 1.53)	1.17 (0.82, 1.65)	1.09 (0.77, 1.54)
	42-63 hours/week	1.31 (0.98, 1.76)	1.36 (1.02, 1.83)	1.22 (0.91, 1.65)
	≥ 63 hours/week	1.63 (1.25, 2.13)	1.60 (1.23, 2.11)	1.60 (1.23, 2.11)
	Ptrend value	< 0.001	< 0.001	< 0.001
Smartphone unlock frequency, continuous variable	Per 50 times/week	1.04 (1.02, 1.05)	1.031 (1.02, 1.05)	1.03 (1.01, 1.04)
Smartphone unlock frequency, categorical variable	0-50 times/week	1 (reference)	1 (reference)	1 (reference)
	50-150 times/week	1.12 (0.85, 1.50)	1.07 (0.80, 1.43)	0.98 (0.73, 1.31)
	150-400 times/week	1.45 (1.09, 1.96)	1.41 (1.05, 1.90)	1.33 (0.99, 1.79)
	≥ 400 times/week	1.77 (1.32, 2.37)	1.63 (1.21, 2.19)	1.48 (1.11, 2.00)
	Ptrend value	< 0.001	< 0.001	0.001

¹Model 1, adjusted for gender, grade, race, registered permanent residence, siblings, and parental educational attainment.

²Model 2, adjusted for gender, grade, race, registered permanent residence, siblings, parental educational attainment, current smoking, current drinking, physical activity, and rational diet.

³Model 3, adjusted for gender, grade, race, registered permanent residence, siblings, parental educational attainment, current smoking, current drinking, physical activity, rational diet, family disasters, hospitalization experience, failed exams, and failed relationships.

OR: Odds ratio; CI: Confidence interval.