Table 1. Descriptive Statistics.
| Variable | No. (%) | ||||||
|---|---|---|---|---|---|---|---|
| Overall | MZF | DZF | MZM | DZM | DZOS, female | DZOS, male | |
| Twins Early Development Study | |||||||
| No. of pairs | 4855 | 1028 | 898 | 724 | 673 | 766 | 766 |
| SPEQ descriptives, mean (SD) | |||||||
| Paranoia | 12.06 (10.52) | 12.24 (10.91) | 12.12 (10.29) | 10.83 (9.58) | 11.62 (10.27) | 13.12 (11.02) | 12.24 (10.72) |
| Hallucinations | 4.70 (6.09) | 4.71 (5.96) | 4.77 (6.22) | 4.24 (5.99) | 4.24 (5.66) | 5.60 (6.58) | 4.57 (5.99) |
| Cognitive disorganization | 3.96 (2.86) | 4.32 (2.86) | 4.55 (2.87) | 3.18 (2.68) | 3.38 (2.76) | 4.50 (2.90) | 3.51 (2.70) |
| Grandiosity | 5.37 (4.49) | 4.94 (4.33) | 4.68 (4.15) | 5.95 (4.64) | 5.99 (4.55) | 4.93 (4.36) | 6.11 (4.74) |
| Anhedonia (reversed) | 16.71 (7.87) | 14.98 (7.38) | 15.36 (7.46) | 18.69 (7.95) | 18.98 (7.85) | 14.98 (7.52) | 18.55 (7.93) |
| Negative symptoms | 2.82 (3.82) | 2.53 (3.57) | 2.68 (3.90) | 2.75 (3.47) | 3.08 (4.05) | 2.44 (3.51) | 3.57 (4.33) |
| Exposure frequencies | |||||||
| Being bullied | 1282 (16.5) | 258 (15.2) | 193 (13.4) | 240 (20.7) | 200 (18.4) | 174 (14.5) | 217 (18.1) |
| Dependent stressful life events | 885 (9.7) | 171 (8.8) | 197 (11.6) | 127 (9.4) | 112 (8.8) | 140 (9.6) | 138 (9.7) |
| Tobacco use | 1714 (23.6) | 337 (23.2) | 324 (24.4) | 226 (20.3) | 231 (22.1) | 314 (26.9) | 282 (24.2) |
| Cannabis use | 725 (10.0) | 94 (6.5) | 113 (8.6) | 129 (11.4) | 114 (11.0) | 123 (10.5) | 152 (13.2) |
| Low birth weight | 1422 (15.0) | 398 (19.8) | 232 (13.3) | 235 (16.7) | 159 (12.0) | 210 (14.0) | 188 (12.5) |
| No. of exposures | |||||||
| 0 | 5501 (56.7) | 1114 (54.2) | 1058 (58.9) | 784 (54.1) | 795 (59.1) | 868 (56.7) | 882 (57.6) |
| 1 | 2861 (29.5) | 690 (33.6) | 505 (28.1) | 451 (31.1) | 366 (27.2) | 440 (28.7) | 409 (26.7) |
| 2 | 958 (9.9) | 196 (9.5) | 164 (9.1) | 146 (10.1) | 119 (8.8) | 161 (10.5) | 172 (11.2) |
| 3 | 313 (3.2) | 48 (2.3) | 52 (2.9) | 55 (3.8) | 52 (3.9) | 53 (3.5) | 53 (3.5) |
| 4 | 73 (0.8) | 8 (0.4) | 15 (0.8) | 11 (0.8) | 14 (1.0) | 10 (0.7) | 15 (1.0) |
| 5 | 4 (0.0) | 0 (0.0) | 2 (0.1) | 1 (0.1) | 0 (0.0) | 0 (0.0) | 1 (0.1) |
| Child and Adolescent Twin Study in Sweden | |||||||
| No. of pairs | 6435 | 1133 | 1225 | 834 | 1027 | 1108 | 1108 |
| APSS descriptives, mean (SD) | |||||||
| Self-report APSS | 1.13 (1.85) | 1.22 (1.86) | 1.23 (1.85) | 0.99 (1.67) | 1.02 (1.89) | 1.22 (1.95) | 0.98 (1.78) |
| Parent report APSS | 0.14 (0.40) | 0.14 (0.35) | 0.15 (0.43) | 0.16 (0.43) | 0.16 (0.47) | 0.11 (0.32) | 0.12 (0.37) |
| Exposure frequencies | |||||||
| Being bullied | 2450 (22.8) | 426 (22.8) | 481 (24.0) | 297 (21.3) | 353 (20.1) | 478 (24.9) | 415 (23.0) |
| Dependent life events | 3154 (31.9) | 602 (32.0) | 740 (38.1) | 270 (22.7) | 366 (26.1) | 756 (38.4) | 420 (28.2) |
| Low birth weight | 2393 (14.7) | 556 (19.7) | 435 (14.3) | 340 (16.2) | 335 (13.0) | 431 (14.2) | 296 (11.0) |
| Tobacco use | 3373 (25.5) | 550 (24.1) | 642 (25.7) | 373 (21.8) | 547 (25.6) | 691 (28.8) | 570 (26.1) |
| Cannabis use | 687 (5.2) | 84 (3.7) | 117 (4.7) | 98 (5.7) | 139 (6.5) | 93 (3.9) | 156 (7.1) |
| No. of exposures | |||||||
| 0 | 8204 (47.9) | 1324 (44.7) | 1448 (45.1) | 1126 (51.2) | 1408 (52.1) | 1429 (44.5) | 1469 (51.6) |
| 1 | 6337 (37.0) | 1148 (38.8) | 1236 (38.5) | 817 (37.1) | 924 (34.2) | 1231 (38.4) | 981 (34.4) |
| 2 | 2110 (12.3) | 404 (13.6) | 418 (13.0) | 214 (9.7) | 308 (11.4) | 438 (13.7) | 328 (11.5) |
| 3 | 441 (2.6) | 78 (2.6) | 97 (3.0) | 43 (2.0) | 60 (2.2) | 98 (3.1) | 65 (2.3) |
| 4+ | 44 (0.3) | 7 (0.2) | 13 (0.4) | NAa (0.0) | 5 (0.2) | 12 (0.4) | 6 (0.2) |
Abbreviations: APSS, Adolescent Psychotic-Like Symptom Screener; DZF, dizygotic female twins; DZM, dizygotic male twins; DZOS, dizygotic opposite-sex twin pair; MZF, monozygotic female twins; MZM, monozygotic male twins; NA, not applicable; SPEQ, Specific Psychotic Experiences Questionnaire.
a
Frequency not shown due to low number.