Mental Health, Smartphone Use Type, and Screen Time Among Adolescents in South Korea

Figures & data

Table 1 General Characteristics and Smartphone Usage Duration in Each Group Classified According to Purpose

Variables	Total (n=54,243)	SI Group (n=25,740)	NSI Group (n=28,503)	p-value
	Mean±SD or N(%)	Mean±SD or N(%)	Mean±SD or N(%)
Age (years)	15.14±0.02	15.20±0.03	15.08±0.03	<0.001*
Sex				<0.001*
Male	26,725(50.5)	8931(36.2)	17,794(63.3)
Female	27,518(49.5)	16,809(63.8)	10,709(36.7)
Area of residence				0.632
Rural	3028(4.6)	1428(4.4)	1707(4.7)
Small city	22,242(43.8)	10,867(44.2)	12,159(43.5)
Large city	27,052(51.6)	13,445(51.4)	14,637(51.8)
Socio-economic status				<0.001*
Low	1302(2.4)	595(2.4)	707(2.4)
Low-middle	6421(11.6)	2944(11.2)	3477(12.1)
Middle	25,155(46.0)	12,069(46.6)	13,086(45.5)
High-middle	15,918(29.7)	7634(29.8)	8284(29.5)
High	5447(10.2)	2498(9.9)	2949(10.5)
Academic achievement				<0.001*
Low	5042(9.4)	2514(10.0)	2528(8.8)
Low-middle	11,825(21.8)	5854(22.9)	5971(20.9)
Middle	15,621(29.0)	7466(29.1)	8155(28.8)
High-middle	14,354(26.3)	6756(25.9)	7598(26.7)
High	7401(13.5)	3150(12.1)	4251(14.8)
Smartphone screen time on weekdays				<0.001*
< 2 hours	14,428(26.7)	5412(21.1)	9016(31.6)
≥ 2 hours but < 4 hours	22,612(42.1)	10,581(41.5)	12,031(42.7)
≥ 4 hours	17,203(31.2)	9747(37.4)	7456(25.7)
Smartphone screen time on weekends				<0.001*
< 2 hours	5829(11.0)	1863(7.5)	3966(14.2)
≥ 2 hours but < 4 hours	14,589(27.6)	6073(24.4)	8516(30.4)
≥ 4 hours	33,825(61.4)	17,804(68.1)	16,021(55.3)

Notes: Weighted percentages following complex sample analysis. *p<0.001.

Table 2 Self-Reported Mental Health of Participants According to the Purpose of Smartphone Use

Variables	Total (n=54,243)	SI Group (n=25,740)	NSI Group (n=28,503)	p-value
	N(%)	N(%)	N(%)
Stress perception				<0.001*
High	20,427(37.5)	10,244(39.5)	10,183(35.7)
Low	33,816(62.5)	15,496(60.5)	18,320(64.3)
Sleep dissatisfaction				<0.001*
Yes	40,717(75.9)	20,470(80.2)	20,247(72.0)
No	13,526(24.1)	5270(19.8)	8256(28.0)
Depressive symptoms				<0.001*
Yes	13,730(25.4)	7418(28.8)	6312(22.2)
No	40,513(74.6)	18,322(71.2)	22,191(77.8)
Suicidal ideation				<0.001*
Yes	6647(12.2)	3458(13.3)	3189(11.1)
No	47,596(87.8)	22,282(86.7)	25,314(88.9)
Suicide plan				0.054
Yes	2072(3.8)	1026(3.9)	1046(3.6)
No	52,171(96.2)	24,714(96.1)	27,457(96.4)
Suicide attempt				<0.001*
Yes	1361(2.5)	719(2.7)	642(2.2)
No	52,882(97.5)	25,021(97.3)	27,861(97.8)

Notes: Weighted percentages following complex sample analysis. *p<0.001.

Table 3 Associations of Self-Reported Mental Health with the Smartphone Purpose and Screen Time on Weekdays

Variables	SI Group	NSI Group
	OR (95% CI)	OR (95% CI)
Stress perception
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	1.029 (0.963–1.099)	0.985 (0.929–1.044)
≥ 4 hours	1.216 (1.135–1.302)	1.156 (1.079–1.239)
Sleep dissatisfaction
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.986 (0.904–1.075)	1.074 (1.005–1.146)
≥ 4 hours	1.103 (1.008–1.208)	1.141 (1.050–1.240)
Depressive symptoms
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	1.014 (0.937–1.098)	1.113 (1.039–1.194)
≥ 4 hours	1.385 (1.275–1.504)	1.289 (1.192–1.393)
Suicidal ideation
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.942 (0.854–1.039)	1.066 (0.973–1.168)
≥ 4 hours	1.248 (1.134–1.374)	1.315 (1.181–1.465)
Suicide plan
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.924 (0.774–1.102)	0.968 (0.831–1.128)
≥ 4 hours	1.231 (1.027–1.476)	1.344 (1.136–1.592)
Suicide attempt
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.902 (0.720–1.130)	1.003 (0.817–1.233)
≥ 4 hours	1.437 (1.146–1.801)	1.547 (1.236–1.937)

Notes: Odds ratio (OR) and 95% confidence interval (CI) was estimated with multivariate logistic regression analysis adjusting for sex, age, socio-economic status, and academic achievement. All the variables presented p-value < 0.001. “Reference” indicates the reference time for comparing the OR. Significant ORs are highlighted in bold.

Table 4 Associations of Self-Reported Mental Health with the Smartphone Purpose and Screen Time on Weekends

Variables	SI Group	NSI Group
	OR (95% CI)	OR (95% CI)
Stress perception
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	1.058 (0.948–1.180)	0.910 (0.838–0.988)
≥ 4 hours	1.186 (1.069–1.315)	1.111 (1.027–1.202)
Sleep dissatisfaction
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	1.154 (1.018–1.309)	1.134 (1.044–1.232)
≥ 4 hours	1.331 (1.185–1.494)	1.300 (1.199–1.409)
Depressive symptoms
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	1.087 (0.963–1.227)	0.942 (0.854–1.038)
≥ 4 hours	1.288 (1.149–1.444)	1.115 (1.019–1.219)
Suicidal ideation
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.861 (0.743–1.009)	0.877 (0.773–0.995)
≥ 4 hours	1.083 (0.941–1.246)	1.122 (0.999–1.260)
Suicide plan
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.802 (0.615–1.046)*	0.665 (0.547–0.808)
≥ 4 hours	0.934 (0.732–1.192)*	0.803 (0.677–0.953)
Suicide attempt
< 2 hours	Reference	Reference
≥ 2 hours but < 4 hours	0.620 (0.439–0.874)	0.738 (0.558–0.975)
≥ 4 hours	0.871 (0.647–1.171)	1.031 (0.812–1.308)

Notes: Odds ratio (OR) and 95% confidence interval (CI) was estimated with multivariate logistic regression analysis adjusting for sex, age, socio-economic status, and academic achievement. All the variables presented p-value < 0.001, except *p-value > 0.05. “Reference” indicates the reference time for comparing the OR. Significant ORs are highlighted in bold.