The authors have no potential conflicts of interest to disclose.
Author Contributions
Conceptualization: Hae Ran Kim, Mi Ah Han. Data curation: Hae Ran Kim, Mi Ah Han. Formal analysis: Hae Ran Kim, Mi Ah Han. Investigation: Hae Ran Kim, Mi Ah Han. Methodology: Hae Ran Kim, Mi Ah Han. Project administration: Hae Ran Kim, Mi Ah Han. Resources: Hae Ran Kim, Mi Ah Han. Software: Hae Ran Kim, Mi Ah Han. Supervision: Mi Ah Han. Validation: Hae Ran Kim, Mi Ah Han. Visualization: Hae Ran Kim, Mi Ah Han. Writing—original draft: Hae Ran Kim. Writing—review & editing: Hae Ran Kim, Mi Ah Han.
Variables |
Smoking |
Drinking |
Physical inactivity ≥3 days/week |
Skipping breakfast ≥5 times/week |
Eating fast food ≥3 times/week |
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---|---|---|---|---|---|---|---|---|---|---|
Total, N (%) | 3,239 (6.2) | OR (95% CI)* | 8,544 (16.3) | OR (95% CI)* | 46,815 (86.3) | OR (95% CI)* | 12,781 (37.2) | OR (95% CI)* | 10,900 (20.5) | OR (95% CI)* |
Number of hours spent using a smartphone on weekdays | ||||||||||
<2 | 503 (3.8) | 1.00 | 1,490 (10.7) | 1.00 | 12,274 (85.3) | 1.00 | 2,622 (34.5) | 1.00 | 2,143 (15.0) | 1.00 |
>2, <4 | 1,013 (4.8) | 1.27 (1.14–1.43) | 3,181 (14.5) | 1.43 (1.34–1.54) | 19,485 (86.4) | 0.99 (0.92–1.06) | 5,075 (35.7) | 1.03 (0.96–1.10) | 4,315 (19.7) | 1.41 (1.33–1.49) |
≥4 | 1,723 (10.3) | 2.92 (2.60–3.27) | 3,873 (23.4) | 2.60 (2.41–2.79) | 15,056 (87.1) | 0.99 (0.91–1.07) | 5,084 (40.6) | 1.21 (1.13–1.29) | 4,442 (26.2) | 2.03 (1.91–2.16) |
Number of hours spent using a smartphone on weekends | ||||||||||
<4 | 857 (4.5) | 1.00 | 2,337 (11.9) | 1.00 | 17,379 (85.1) | 1.00 | 4,004 (35.1) | 1.00 | 3,331 (16.7) | 1.00 |
>4, <8 | 1,096 (5.5) | 1.29 (1.18–1.42) | 3,322 (16.1) | 1.44 (1.36–1.53) | 18,514 (86.9) | 0.99 (0.93–1.06) | 4,985 (35.8) | 1.01 (0.96–1.07) | 4,337 (20.8) | 1.34 (1.27–1.41) |
≥8 | 1,286 (10.8) | 2.85 (2.60–3.13) | 2,885 (24.3) | 2.53 (2.36–2.72) | 10,922 (87.4) | 0.96 (0.88–1.04) | 3,792 (42.3) | 1.28 (1.21–1.36) | 3,232 (26.6) | 1.86 (1.75–1.97) |
Main purpose for using a smartphone | ||||||||||
Education | 193 (4.9) | 1.00 | 535 (13.3) | 1.00 | 3,631 (86.7) | 1.00 | 827 (35.8) | 1.00 | 715 (17.8) | 1.00 |
Communication | 1,999 (8.2) | 2.63 (2.25–3.07) | 5,018 (20.3) | 2.27 (2.05–2.52) | 22,242 (86.9) | 0.80 (0.72–0.90) | 6,328 (37.0) | 1.00 (0.91–1.09) | 5,545 (22.1) | 1.37 (1.25–1.50) |
Enjoyment | 1,047 (4.5) | 1.02 (0.87–1.20) | 2,991 (12.6) | 1.18 (1.06–1.32) | 20,942 (85.6) | 1.02 (0.91–1.14) | 5,626 (37.7) | 0.99 (0.90–1.09) | 4,640 (19.2) | 1.12 (1.02–1.22) |
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||||||||||
Variables |
Sleep disturbances |
Stress |
Depressive symptoms |
Suicidal ideation |
Suicide attempt |
|||||
Total, N (%) | 40,990 (75.9) | OR (95% CI)* | 20,586 (37.6) | OR (95% CI)* | 13,850 (25.4) | OR (95% CI)† | 6,714 (12.2) | OR (95% CI)‡ | 1,387 (2.5) | OR (95% CI)‡ |
|
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Number of hours spent using a smartphone on weekdays | ||||||||||
<2 | 10,379 (72.6) | 1.00 | 4,910 (34.0) | 1.00 | 3,057 (21.1) | 1.00 | 1,477 (10.3) | 1.00 | 294 (2.0) | 1.00 |
>2, <4 | 17,009 (75.7) | 1.06 (1.01–1.12) | 8,213 (36.0) | 1.00 (0.96–1.05) | 5,384 (23.8) | 1.08 (1.03–1.14) | 2,542 (11.0) | 0.94 (0.87–1.02) | 462 (2.0) | 0.85 (0.72–0.98) |
≥4 | 13,602 (79.0) | 1.20 (1.13–1.28) | 7,463 (42.7) | 1.20 (1.14–1.26) | 5,409 (31.2) | 1.37 (1.29–1.45) | 2,695 (15.4) | 1.06 (0.98–1.15) | 631 (3.6) | 1.15 (0.98–1.35) |
Number of hours spent using a smartphone on weekends | ||||||||||
<4 | 14,472 (71.6) | 1.00 | 6,736 (33.0) | 1.00 | 4,351 (21.5) | 1.00 | 2,027 (10.0) | 1.00 | 416 (2.0) | 1.00 |
>4, <8 | 16,492 (77.5) | 1.19 (1.13–1.25) | 8,096 (37.6) | 1.09 (1.04–1.13) | 5,434 (25.4) | 1.09 (1.04–1.14) | 2,548 (11.7) | 1.00 (0.93–1.07) | 451 (2.1) | 0.83 (0.72–0.96) |
≥8 | 10,026 (80.5) | 1.37 (1.29–1.46) | 5,754 (45.4) | 1.38 (1.31–1.45) | 4,065 (32.4) | 1.33 (1.25–1.41) | 2,139 (17.0) | 1.22 (1.12–1.32) | 520 (4.1) | 1.28 (1.10–1.49) |
Main purpose for using a smartphone | ||||||||||
Education | 3,035 (73.5) | 1.00 | 1,558 (37.2) | 1.00 | 998 (23.7) | 1.00 | 442 (10.4) | 1.00 | 93 (2.2) | 1.00 |
Communication | 20,470 (80.2) | 1.36 (1.26–1.47) | 10,244 (39.5) | 0.94 (0.88–1.00) | 7,418 (28.8) | 1.17 (1.08–1.27) | 3,458 (13.3) | 1.05 (0.93–1.19) | 719 (2.7) | 0.91 (0.73–1.13) |
Enjoyment | 17,485 (71.8) | 1.07 (0.99–1.16) | 8,784 (35.6) | 0.95 (0.89–1.01) | 5,434 (22.1) | 0.91 (0.84–0.99) | 2,814 (11.3) | 1.11 (0.98–1.25) | 575 (2.3) | 0.94 (0.76–1.17) |
* adjusted for gender, school year, perceived academic record, family structure, parental educational level, perceived economic status, and place of residence,
† adjusted for gender, school year, perceived school record, family structure, parental educational level, perceived economic status, place of residence, and stress,
Variables |
Smoking |
Drinking |
Physical inactivity ≥3 days/week |
Skipping breakfast ≥5 times/week |
Eating fast food ≥3 times/week |
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---|---|---|---|---|---|---|---|---|---|---|
Total, N (%) | N (%) | OR (95% CI)* | N (%) | OR (95% CI)* | N (%) | OR (95% CI)* | N (%) | OR (95% CI)* | N (%) | OR (95% CI)* |
Severe conflicts with family owing to smartphone use | ||||||||||
No | 2,437 (6.1) | 1.00 | 6,558 (16.1) | 1.00 | 36,333 (86.0) | 1.00 | 10,063 (37.8) | 1.00 | 8,003 (19.2) | 1.00 |
Yes | 802 (6.8) | 1.37 (1.25–1.49) | 1,986 (16.9) | 1.27 (1.20–1.35) | 10,482 (87.5) | 1.17 (1.09–1.25) | 2,718 (35.2) | 0.89 (0.84–0.94) | 2,897 (24.8) | 1.41 (1.35–1.48) |
Severe conflicts with friends owing to smartphone use | ||||||||||
No | 2,375 (6.1) | 1.00 | 6,057 (15.3) | 1.00 | 34,658 (84.9) | 1.00 | 9,626 (37.7) | 1.00 | 7,636 (19.0) | 1.00 |
Yes | 864 (6.5) | 1.03 (0.94–1.13) | 2,487 (19.0) | 1.10 (1.05–1.17) | 12,157 (90.4) | 1.36 (1.26–1.46) | 3,155 (35.9) | 0.96 (0.91–1.01) | 3,264 (24.7) | 1.38 (1.32–1.45) |
Academic problems owing to smartphone use | ||||||||||
No | 2,957 (5.9) | 1.00 | 8,042 (15.9) | 1.00 | 45,181 (86.3) | 1.00 | 12,243 (37.1) | 1.00 | 10,335 (20.2) | 1.00 |
Yes | 282 (15.3) | 3.49 (2.99–4.10) | 502 (26.9) 2 | .37 (2.12–2.64) | 1,634 (85.9) | 0.96 (0.83–1.12) | 538 (39.5) 1 | .06 (0.94–1.20) | 565 (29.7) 1 | .67 (1.51–1.85) |
|
||||||||||
Variables |
Sleep disturbances |
Stress |
Depressive symptoms |
Suicidal ideation |
Suicide attempt |
|||||
Total, N (%) | N (%) | OR (95% CI)* | N (%) | OR (95% CI)* | N (%) | OR (95% CI)† | N (%) | OR (95% CI)‡ | N (%) | OR (95% CI)‡ |
|
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Severe conflicts with family owing to smartphone use | ||||||||||
No | 31,456 (74.7) | 1.00 | 14,617 (34.2) | 1.00 | 9,461 (22.3) | 1.00 | 4,245 (9.9) | 1.00 | 858 (2.0) | 1.00 |
Yes | 9,534 (80.0) | 1.43 (1.36–1.52) | 5,969 (49.2) | 1.90 (1.82–1.99) | 4,389 (36.1) | 1.65 (1.57–1.73) | 2,469 (20.2) | 1.56 (1.47–1.66) | 529 (4.3) | 1.42 (1.26–1.60) |
Severe conflicts with friends owing to smartphone use | ||||||||||
No | 29,696 (73.0) | 1.00 | 13,960 (33.7) | 1.00 | 9,105 (22.2) | 1.00 | 4,355 (10.5) | 1.00 | 964 (2.3) | 1.00 |
Yes | 11,294 (84.2) | 1.54 (1.46–1.63) | 6,626 (48.7) | 1.65 (1.58–1.72) | 4,745 (34.7) | 1.46 (1.39–1.53) | 2,359 (17.1) | 1.22 (1.14–1.30) | 423 (3.0) | 0.93 (0.82–1.05) |
Academic problems owing to smartphone use | ||||||||||
No | 39,458 (75.7) | 1.00 | 19,457 (36.8) | 1.00 | 12,866 (24.5) | 1.00 | 6,190 (11.7) | 1.00 | 1,224 (2.3) | 1.00 |
Yes | 1,532 (80.8) | 1.39 (1.23–1.57) | 1,129 (58.2) | 2.33 (2.11–2.57) | 984 (52.1) 2 | .67 (2.41–2.96) | 524 (27.5) | 1.42 (1.25–1.62) | 163 (8.4) | 1.89 (1.55–2.30) |
* adjusted for gender, school year, perceived academic record, family structure, parental educational level, perceived economic status, and place of residence,
† adjusted for gender, school year, perceived academic record, family structure, parental educational level, perceived economic status, place of residence, and stress.