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Table 1 Sociodemographic characteristics

From: Assessment of life factors affecting the experience of depressive symptoms in adolescents: a secondary analysis using the Korea Youth Risk Behavior Survey

Variables Grade 7 Grade 8 Grade 9 Grade 10 Grade 11 Grade 12 p-value
(n: 7975) (n: 7723) (n: 8014) (n: 7498) (n: 7242) (n: 7754)
Age (in years) 12.50 ± 0.51 13.52 ± 0.52 14.51 ± 0.52 15.51 ± 0.52 16.50 ± 0.52 17.47 ± 0.52  
Gender, Girls 3879 (48.6) 3803 (49.2) 3865 (48.2) 3619 (48.3) 3544 (48.9) 3723 (48.0) 0.637
School type  < 0.01
 Co-educational school 5878 (73.7) 5664 (73.3) 5900 (73.6) 4377 (58.4) 4204 (48.1) 4491 (57.9)  
 Boys school 1079 (13.5) 1074 (13.9) 1095 (13.7) 1532 (20.4) 1498 (20.7) 1604 (20.7)
 Girls school 1018 (12.8) 985 (12.8) 1019 (12.7) 1589 (21.2) 154 (21.3) 1659 (21.4)
Multicultural family  < 0.01
 Yes 170 (2.8) 130 (2.4) 103 (1.9) 62 (1.3) 58 (1.3) 57 (1.3)  
 No 5803 (97.2) 5213 (97.6) 5213 (98.1) 4617 (98.7) 4256 (98.7) 4371 (98.7)
Perceived academic performance  < 0.01
 Upper 1468 (18.4) 1183 (15.3) 1323 (16.5) 737 (9.8) 702 (9.7) 829 (10.7)  
 Upper middle 2493 (31.3) 2068 (26.8) 2083 (26.0) 1753 (23.4) 1665 (23.0) 1857 (23.9)
 Middle 2509 (31.5) 2238 (29.0) 2093 (26.1) 2343 (31.2) 2379 (32.9) 2521 (32.5)
 Lower middle 1143 (14.3) 1616 (20.9) 1768 (22.1) 1861 (24.8) 1773 (24.5) 1844 (23.8)
 Lower 362 (4.5) 618 (8.0) 747 (9.3) 804 (10.7) 723 (10.0) 703 (9.1)
Perceived household economic status  < 0.01
 Upper 1303 (16.3) 965 (12.5) 874 (10.9) 652 (8.7) 597 (8.2) 578 (7.5)  
 Upper middle 2635 (33.0) 2350 (30.4) 2344 (29.2) 2071 (27.6) 1894 (26.2) 1946 (25.1)
 Middle 3425 (42.9) 3638 (47.1) 392 (48.8) 3761 (50.2) 3615 (49.9) 3952 (51.0)
 Lower middle 542 (6.8) 661 (8.6) 751 (9.4) 842 (11.2) 933 (12.9) 1055 (13.6)
 Lower 70 (0.9) 109 (1.4) 133 (1.7) 172 (2.3) 203 (2.8) 223 (2.9)
Dietary behaviora (days) 4.28 (± 2.74) 4.04 (± 2.75) 3.95 (± 2.77) 4.02 (± 2.68) 3.83 (± 2.68) 4.01 (± 2.70)  < 0.01
Perceived health status  < 0.01
 Very healthy 2438 (30.6) 2134 (27.6) 2292 (28.6) 1932 (25.8) 1714 (23.7) 1860 (24.0)  
 Healthy 3736 (46.8) 3544 (45.9) 3527 (44.0) 3401 (45.4) 3151 (43.5) 3200 (41.3)
 Normal 1528 (19.2) 1667 (21.6) 1715 (21.4) 1604 (21.4) 1753 (24.2) 1933 (24.9)
 Unhealthy 263 (3.3) 358 (4.6) 455 (5.7) 532 (7.1) 575 (7.9) 712 (9.2)
 Very unhealthy 10 (0.1) 20 (0.3) 25 (0.3) 29 (0.4) 49 (0.7) 49 (0.6)
Perception of body shape  < 0.01
 Very skinny 332 (4.2) 336 (4.4) 359 (4.5) 341 (4.5) 293 (4.0) 285 (3.7)  
 Skinny 1802 (22.6) 1756 (22.7) 1770 (22.1) 1582 (21.1) 1465 (20.2) 1480 (19.1)
 Average 2944 (37.5) 2898 (37.5) 2965 (37.0) 2680 (35.7) 2572 (35.5) 2727 (35.2)
 Obese 2395 (30.0) 2309 (29.9) 2465 (30.8) 2399 (32.0) 2682 (34.6) 2682 (34.6)
 Very obese 452 (5.7) 424 (5.5) 455 (5.7) 496 (6.6) 514 (7.1) 580 (7.5)
Physical activityb (in days) 2.32 ± 2.21 2.26 ± 2.16 2.20 ± 2.19 1.83 ± 2.02 1.84 ± 2.01 1.69 ± 2.00  < 0.01
Time spent studying (WDc) (in mins) 376.68 ± 242.87 415.80 ± 242.87 425.80 ± 237.63 520.05 ± 263.81 516.83 ± 251.16 550.70 ± 252.37  < 0.01
Time spent studying (WKd) (in mins) 148.56 ± 155.73 186.37 ± 178.95 191.13 ± 187.34 266.74 ± 225.93 276.76 ± 232.37 339.08 ± 266.73  < 0.01
Duration of Internet use (WDc) (in mins) 111.75 ± 112.57 122.82 ± 122.45 117.96 ± 120.20 104.29 ± 109.48 103.07 ± 110.23 97.73 ± 105.12  < 0.01
Duration of Internet use (WKd) (in mins) 186.55 ± 163.00 208.39 ± 174.33 202.43 ± 176.93 189.43 ± 161.08 174.93 ± 161.61 163.74 ± 152.89  < 0.01
Perceived level of stress  < 0.01
 Very much 643 (8.1) 754 (9.8) 820 (10.2) 822 (11.0) 874 (12.1) 976 (12.6)  
 A lot 2021 (25.3) 2156 (27.9) 2143 (26.7) 2166 (28.9) 2175 (30.0) 2264 (29.2)
 A little 3276 (41.1) 3204 (41.5) 3407 (42.5) 3203 (42.7) 2991 (41.3) 3223 (41.6)
 Not much 1625 (20.4) 1307 (16.9) 1353 (16.9) 1044 (13.9) 989 (13.7) 1057 (13.6)
 Not at all 410 (5.1) 302 (3.9) 291 (3.6) 263 (3.5) 213 (2.9) 234 (3.0)
Depressive symptoms, (yes) 1752 (22.0) 2075 (26.9) 2228 (27.8) 1993 (26.6) 2024 (27.9) 2294 (29.6)  < 0.01
  1. Each number is presented as the mean (standard deviation) or sample size (ratio by group)
  2. aDietary behavior: Number of days per week on which participants ate breakfast
  3. bPhysical activity: number of days per week participants engaged in physical activity for at least 60 min per day
  4. cWD: weekday
  5. dWK: weekend