Table 1 Self-harm prevalence in different demographic groups
From: Gender differences in self-harm and drinking behaviors among high school students in Beijing, China
|  | Total | Frequency of self-harm (in past 12 months) | G | P | |||
|---|---|---|---|---|---|---|---|
Never | Once | Twice or three times | Four times or more | ||||
Boys | |||||||
 Age | |||||||
 12 ~ 13 | 2942 | 2540 (86.3) | 198 (6.7) | 110 (3.7) | 94 (3.2) | −0.041 | 0.007 |
 14 | 2698 | 2277 (84.4) | 202 (7.5) | 127 (4.7) | 92 (3.4) |  |  |
 15 | 2212 | 1904 (86.1) | 145 (6.6) | 90 (4.1) | 73 (3.3) |  |  |
 16 | 3348 | 2896 (86.5) | 200 (6.0) | 128 (3.8) | 124 (3.7) |  |  |
 17 | 3246 | 2857 (88.0) | 181 (5.6) | 118 (3.6) | 90 (2.8) |  |  |
 18 ~ 19 | 1656 | 1443 (87.1) | 84 (5.1) | 70 (4.2) | 59 (3.6) |  |  |
 Setting | |||||||
 Urban | 8100 | 7005 (86.5) | 495 (6.1) | 323 (4.0) | 277 (3.4) | 0.002 | 0.920 |
 Suburban | 8003 | 6913 (86.4) | 515 (6.4) | 320 (4.0) | 255 (3.2) |  |  |
 School type | |||||||
 Key School | 5761 | 5001 (86.8) | 352 (6.1) | 216 (3.7) | 192 (3.3) | 0.023 | 0.306 |
 Non-Key School | 10,342 | 8917 (86.2) | 658 (6.4) | 427 (4.1) | 340 (3.3) |  |  |
 Total | 16,103 | 13,918 (86.4) | 1010 (6.3) | 643 (4.0) | 532 (3.3) |  |  |
Girls | |||||||
 Age | |||||||
 12 ~ 13 | 3106 | 2551 (82.1) | 275 (8.9) | 175 (5.6) | 105 (3.4) | −0.167 | < 0.001 |
 14 | 2468 | 2044 (82.8) | 192 (7.8) | 156 (6.3) | 76 (3.1) |  |  |
 14 | 2246 | 1923 (85.6) | 167 (7.4) | 106 (4.7) | 50 (2.2) |  |  |
 15 | 3559 | 3126 (87.8) | 231 (6.5) | 135 (3.8) | 67 (1.9) |  |  |
 17 | 3202 | 2844 (88.8) | 182 (5.7) | 121 (3.8) | 55 (1.7) |  |  |
 18 ~ 19 | 1677 | 1527 (91.1) | 72 (4.3) | 51 (3.0) | 27 (1.2) |  |  |
 Setting | |||||||
 Urban | 8141 | 6996 (85.9) | 557 (6.8) | 386 (4.7) | 202 (2.5) | −0.024 | 0.274 |
 Suburban | 8118 | 7020 (86.5) | 562 (6.9) | 358 (4.4) | 178 (2.2) |  |  |
 School type | |||||||
 Key School | 6304 | 5508 (87.4) | 381 (6.0) | 269 (4.3) | 146 (2.3) | 0.075 | 0.001 |
 Non-Key School | 9955 | 8508 (85.5) | 738 (7.4) | 475 (4.8) | 234 (2.4) |  |  |
Total | 16,259 | 14,016 (86.2) | 1119 (6.9) | 744 (4.6) | 380 (2.3) | Â | Â |