Table 1 Basic characteristics of participants

Total (n = 17633)

(n = 5700)

3628 (63.6%)

2072 (36.4%)

(n = 11933)

6186 (51.84%)

5747 (48.16%)

Mean age (SD)

19.95 (1.53)

19.87 (1.54)

20.09 (1.52)

16.17 (1.21)

16.16 (1.20)

16.18 (1.23)

Ethnicity

 Han

2600 (45.6%)

1656 (45.6%)

944 (45.6%)

11,720 (98.22%)

6077 (98.24%)

5643 (98.19%)

 Others ^ (Tibetan, Hui, etc.)

3057 (53.6%)

1409 (53.8%)

1108 (54.3%)

213 (1.78%)

109 (1.76%)

104 (1.81%)

 Missing

43 (0.8%)

23 (0.6%)

20 (1.0%)

-

-

-

Only-child status

 No

4250 (74.6%)

2853 (78.6%)

1389 (67.4%)

8113 (67.99%)

4789 (77.42%)

3324 (57.84%)

 Yes

1145 (20.1%)

618 (17.0%)

527 (25.4%)

3820 (32.01%)

1397 (22.58%)

2423 (42.16%)

 Missing

305 (5.3%)

157 (4.3%)

148 (7.1%)

-

-

-

Family economy status

 Rich

294 (5.2%)

169 (4.7%)

125 (6.0%)

1961 (16.43%)

986 (15.94%)

975 (16.97%)

 General

4316 (75.7%)

2826 (77.9%)

1490 (71.9%)

9064 (75.96%)

4761 (76.96%)

4303 (74.87%)

 Poor

1009 (17.7%)

578 (15.9%)

431 (20.8%)

908 (7.61%)

439 (7.10%)

469 (8.16%)

 Missing

81 (1.4%)

55 (1.5%)

26 (1.3%)

-

-

-

Self-perceived health

 Good

2587 (45.4%)

1560 (43.0%)

1027 (49.6%)

6754 (56.60%)

3211(51.91%)

3543 (61.65%)

 General

2895 (50.8%)

1939 (53.4%)

956 (46.1%)

2898 (24.29%)

1674 (27.06%)

1224 (21.30%)

 Bad

192 (3.4%)

114 (3.1%)

78 (3.8%)

2281 (19.11%)

1301 (21.03%)

980 (17.05%)

 Missing

26 (0.5%)

15 (0.4%)

11 (0.5)

-

-

-

Weekly physical exercise

 Never

821 (14.4%)

602 (16.6%)

219 (10.6%)

607 (5.09%)

297 (4.80%)

310 (5.39%)

 1–2 times

3146 (55.2%)

2130 (58.7%)

1016 (49.0%)

4082 (34.21%)

2386 (38.57%)

1696 (29.51%)

 3–5 times

992 (17.4%)

496 (13.7%)

496 (23.9%)

5365 (44.95%)

2785 (45.02%)

2580 (44.89%)

 > 5 times

724 (12.8%)

395 (10.9%)

333 (16.1%)

1879 (15.75%)

718 (11.61%)

1161 (20.21%)

 Missing

12 (0.2)

5 (0.1%)

8 (0.4%)

-

-

-

Relationship with family

 Good

4894 (85.9%)

3132 (86.3%)

1762 (85.0%)

6348 (53.20%)

3342 (54.03%)

3006 (52.31%)

 General

706 (12.4%)

443 (12.2%)

263 (12.7%)

4363 (36.56%)

2270 (36.70%)

2093 (36.42%)

 Poor

58 (1.0%)

32 (0.9%)

26 (1.3%)

1222 (10.24%)

574 (9.27%)

648 (11.27%)

 Missing

42 (0.7%)

21 (0.6%)

21 (1.0%)

-

-

-

Relationship with teachers

 Good

2104 (36.9%)

1279 (35.2%)

825 (39.8%)

3883 (32.54%)

1914 (30.94%)

1969 (34.26%)

 General

3450 (60.5%)

2276 (62.7%)

1174 (56.7%)

6425 (53.84%)

3523 (56.95%)

2902 (50.50%)

 Poor

127 (2.2%)

65 (1.8%)

62 (3.0%)

1625 (13.62%)

749 (12.11%)

876 (15.24%)

 Missing

19 (0.3%)

8 (0.2%)

11 (5.0%)

-

-

-

Grade

 Freshmen

2619 (45.9%)

1745 (48.1%)

874 (42.2%)

-

-

-

 Others

3039 (53.4%)

1860 (51.3%)

1179 (56.9%)

-

-

-

 Missing

42 (0.7%)

23 (0.6%)

19 (0.9%)

-

-

-

Place of residence

 Non plateau

965 (16.9%)

618 (17.0%)

347 (16.7%)

-

-

-

 Plateau

4563 (80.1%)

2914 (80.3%)

1649 (79.6%)

-

-

-

 Missing

172 (3.0%)

96 (2.6%)

76 (3.7%)

-

-

-

Academic pressure

 Low

320 (5.6%)

152 (4.2%)

168 (8.1%)

-

-

-

 Normal

3600 (63.2%)

2249 (62.0%)

1351 (65.2%)

-

-

-

 High

1772 (31.1%)

1221 (33.7%)

551 (26.6%)

-

-

-

 Missing

8 (0.2%)

6 (0.2%)

2 (0.1%)

-

-

-

Relationship with classmates

 Good

2707 (47.5%)

1688 (46.5%)

1019 (49.2%)

-

-

-

 General

2898 (50.9%)

1891 (52.1%)

1007 (48.6%)

-

-

-

 Poor

86 (1.5%)

44 (1.2%)

42 (2.0%)

-

-

-

 Missing

9 (0.2%)

5 (0.1%)

4 (0.2%)

-

-

-

Hopelessness (SD)

6.27 (3.53)

6.21 (3.46)

6.40 (3.67)

-

-

-

Suicide ideation

 No

3413 (61.3%)

2070 (58.2%)

1343 (66.8%)

7800 (65.36%)

4059 (65.62%)

3741 (65.09%)

 Yes

2152 (37.7%)

1485 (41.8%)

667 (33.2%)

4133 (34.64%)

2127 (34.38%)

2006 (34.91%)

 Missing

135

73

62

-

-

-