Table 1.
Demographic characteristics.
| Overall | Only child | First-born | Middle | Last-born | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| (n = 3,744) | (n = 644, 17.2%) | (n = 1,278, 34.1%) | (n = 466, 12.5%) | (n = 1,356, 36.2%) | ||||||
| n | % | n | % | n | % | n | % | n | % | |
| Sex | ||||||||||
| Boys | 1,908 | 51.0 | 324 | 50.3 | 694 | 54.3 | 234 | 50.2 | 656 | 48.4 |
| Girls | 1,836 | 49.0 | 320 | 49.7 | 584 | 45.7 | 232 | 49.8 | 700 | 51.6 |
| Mother's educational attainment | ||||||||||
| High school graduate or less | 956 | 25.5 | 175 | 27.2 | 284 | 22.2 | 137 | 29.4 | 360 | 26.6 |
| Some college | 1,248 | 33.3 | 235 | 36.5 | 427 | 33.4 | 136 | 29.2 | 450 | 33.2 |
| College or University graduate | 610 | 16.3 | 94 | 14.6 | 265 | 20.7 | 58 | 12.5 | 193 | 14.2 |
| Others/unknown | 930 | 24.8 | 140 | 21.7 | 302 | 23.6 | 135 | 29.0 | 353 | 26.0 |
| Mother's age (Mean, SD) | 41.2 | 4.9 | 43.1 | 4.7 | 38.9 | 4.5 | 39.6 | 4.5 | 43.1 | 4.3 |
| Respondent's mental health (K6) | ||||||||||
| <5 | 2,480 | 66.2 | 426 | 66.2 | 835 | 65.3 | 308 | 66.1 | 911 | 67.2 |
| 5 ≤ 13 | 989 | 26.4 | 175 | 27.2 | 344 | 26.9 | 115 | 24.7 | 355 | 26.2 |
| 13+ | 162 | 4.3 | 32 | 5.0 | 56 | 4.4 | 25 | 5.4 | 49 | 3.6 |
| Missing | 113 | 3.0 | 11 | 1.7 | 43 | 3.4 | 18 | 3.9 | 41 | 3.0 |
| Parental history of psychiatric disorder | ||||||||||
| No | 3,472 | 92.7 | 574 | 89.1 | 1,185 | 92.7 | 430 | 92.3 | 1,283 | 94.6 |
| Yes | 272 | 7.3 | 70 | 10.9 | 93 | 7.3 | 36 | 7.7 | 73 | 5.4 |
| Household income (million yen) | ||||||||||
| <3.0 | 187 | 5.0 | 33 | 5.1 | 62 | 4.9 | 30 | 6.4 | 62 | 4.6 |
| 3.0 ≤ 6.0 | 1,181 | 31.5 | 211 | 32.8 | 411 | 32.2 | 163 | 35.0 | 396 | 29.2 |
| 6.0 ≤ 10.0 | 1,382 | 36.9 | 238 | 37.0 | 477 | 37.3 | 153 | 32.8 | 514 | 37.9 |
| 10.0+ | 484 | 12.9 | 94 | 14.6 | 160 | 12.5 | 43 | 9.2 | 187 | 13.8 |
| Missing | 510 | 13.6 | 68 | 10.6 | 168 | 13.2 | 77 | 16.5 | 197 | 14.5 |
| Living with grandparents | ||||||||||
| No | 3,432 | 91.7 | 597 | 92.7 | 1,182 | 92.5 | 422 | 90.6 | 1,231 | 90.8 |
| Yes | 312 | 8.3 | 47 | 7.3 | 96 | 7.5 | 44 | 9.4 | 125 | 9.2 |
| School absences due to illness or trauma | ||||||||||
| No | 2,448 | 65.4 | 429 | 66.6 | 796 | 62.3 | 306 | 65.7 | 917 | 67.6 |
| Yes | 1,296 | 34.7 | 215 | 33.4 | 482 | 37.7 | 160 | 34.3 | 439 | 32.4 |
| Child mental health | ||||||||||
| SDQ | ||||||||||
| Total difficulties | ||||||||||
| Normal | 2,715 | 72.5 | 450 | 69.9 | 892 | 69.8 | 346 | 74.3 | 1,027 | 75.7 |
| Borderline | 411 | 11.0 | 79 | 12.3 | 151 | 11.8 | 45 | 9.7 | 136 | 10.0 |
| Clinical | 495 | 13.2 | 102 | 15.8 | 191 | 15.0 | 56 | 12.0 | 146 | 10.8 |
| Missing | 123 | 3.3 | 13 | 2.0 | 44 | 3.4 | 19 | 4.1 | 47 | 3.5 |
| Emotional symptoms | ||||||||||
| Normal | 2,954 | 78.9 | 499 | 77.5 | 996 | 77.9 | 383 | 82.2 | 1,076 | 79.4 |
| Borderline | 302 | 8.1 | 61 | 9.5 | 104 | 8.1 | 27 | 5.8 | 110 | 8.1 |
| Clinical | 365 | 9.8 | 71 | 11.0 | 134 | 10.5 | 37 | 7.9 | 123 | 9.1 |
| Missing | 123 | 3.3 | 13 | 2.0 | 44 | 3.4 | 19 | 4.1 | 47 | 3.5 |
| Conduct problems | ||||||||||
| Normal | 2,860 | 76.4 | 509 | 79.0 | 938 | 73.4 | 348 | 74.7 | 1,065 | 78.5 |
| Borderline | 335 | 9.0 | 60 | 9.3 | 130 | 10.2 | 39 | 8.4 | 106 | 7.8 |
| Clinical | 426 | 11.4 | 62 | 9.6 | 166 | 13.0 | 60 | 12.9 | 138 | 10.2 |
| Missing | 123 | 3.3 | 13 | 2.0 | 44 | 3.4 | 19 | 4.1 | 47 | 3.5 |
| Hyperactivity/inattention problems | ||||||||||
| Normal | 2,997 | 80.1 | 511 | 79.4 | 998 | 78.1 | 375 | 80.5 | 1,113 | 82.1 |
| Borderline | 237 | 6.3 | 43 | 6.7 | 95 | 7.4 | 20 | 4.3 | 79 | 5.8 |
| Clinical | 388 | 10.4 | 77 | 12.0 | 141 | 11.0 | 53 | 11.4 | 117 | 8.6 |
| Missing | 122 | 3.3 | 13 | 2.0 | 44 | 3.4 | 18 | 3.9 | 47 | 3.5 |
| Peer relationship problems | ||||||||||
| Normal | 2,996 | 80.0 | 464 | 72.1 | 1,024 | 80.1 | 384 | 82.4 | 1,124 | 82.9 |
| Borderline | 285 | 7.6 | 80 | 12.4 | 90 | 7.0 | 25 | 5.4 | 90 | 6.6 |
| Clinical | 340 | 9.1 | 87 | 13.5 | 120 | 9.4 | 38 | 8.2 | 95 | 7.0 |
| Missing | 123 | 3.3 | 13 | 2.0 | 44 | 3.4 | 19 | 4.1 | 47 | 3.5 |
| Prosocial behavior | ||||||||||
| Normal | 2,596 | 69.3 | 452 | 70.2 | 850 | 66.5 | 320 | 68.7 | 974 | 71.8 |
| Borderline | 533 | 14.2 | 89 | 13.8 | 187 | 14.6 | 72 | 15.5 | 185 | 13.6 |
| Clinical | 492 | 13.1 | 90 | 14.0 | 197 | 15.4 | 55 | 11.8 | 150 | 11.1 |
| Missing | 123 | 3.3 | 13 | 2.0 | 44 | 3.4 | 19 | 4.1 | 47 | 3.5 |
| Self-esteem score | ||||||||||
| Not low | 3,299 | 88.1 | 570 | 88.5 | 1,118 | 87.5 | 415 | 89.1 | 1,196 | 88.2 |
| Low | 316 | 8.4 | 54 | 8.4 | 111 | 8.7 | 35 | 7.5 | 116 | 8.6 |
| Missing | 129 | 3.5 | 20 | 3.1 | 49 | 3.8 | 16 | 3.4 | 44 | 3.2 |
| Resilience score | ||||||||||
| Not low | 3,457 | 92.3 | 583 | 90.5 | 1,183 | 92.6 | 427 | 91.6 | 1,264 | 93.2 |
| Low | 285 | 7.6 | 61 | 9.5 | 95 | 7.4 | 38 | 8.2 | 91 | 6.7 |
| Missing | 2 | 0.1 | 0 | 0.0 | 0 | 0.0 | 1 | 0.2 | 1 | 0.1 |
| Happiness score | ||||||||||
| Not low | 3,376 | 90.2 | 589 | 91.5 | 1,138 | 89.1 | 407 | 87.3 | 1,242 | 91.6 |
| Low | 208 | 5.6 | 30 | 4.7 | 78 | 6.1 | 38 | 8.2 | 62 | 4.6 |
| Missing | 160 | 4.3 | 25 | 3.9 | 62 | 4.9 | 21 | 4.5 | 52 | 3.8 |