Summary of the characteristics of the 5166 cohort members with smoking and film data available at approximately age 15 years
| Time point | Characteristic | n | Mean | SD |
| Cohort member age (years) | 5166 | 15.45 | 0.30 | |
| Maternal age in pregnancy (years) | 4921 | 29.23 | 4.54 |
| Time point | Characteristic | Categories | n | % |
| 8 weeks gestation | Housing in pregnancy | Mortgaged | 3960 | 83.02 |
| Owned | 99 | 2.08 | ||
| Council rented | 364 | 7.63 | ||
| Private rented | 222 | 4.65 | ||
| Other | 125 | 2.62 | ||
| Marital status in pregnancy | Married | 3946 | 81.99 | |
| Divorced/separated | 216 | 4.49 | ||
| Widowed | 7 | 0.15 | ||
| Never married | 644 | 13.38 | ||
| 18 weeks gestation | Parity | 0 | 2354 | 49.35 |
| 1 | 1649 | 34.57 | ||
| ≥2 | 767 | 16.08 | ||
| Maternal smoking in pregnancy | No | 3603 | 81.41 | |
| Yes | 823 | 18.59 | ||
| Partner smoking in pregnancy | No | 3275 | 68.86 | |
| Yes | 1481 | 31.14 | ||
| 32 weeks gestation | Social class in pregnancy | V | 119 | 2.59 |
| IV | 582 | 12.68 | ||
| III manual | 1155 | 25.17 | ||
| III non-manual | 1288 | 28.07 | ||
| II | 1248 | 27.20 | ||
| I | 197 | 4.29 | ||
| Financial difficulties in pregnancy | Q1 (score 0) | 1970 | 42.29 | |
| Q2 (score 1–2) | 1172 | 25.16 | ||
| Q3 (score 3–5) | 829 | 17.80 | ||
| Q4 (score 6–15) | 687 | 14.75 | ||
| Maternal education | None/CSE | 530 | 11.10 | |
| Vocational | 362 | 7.58 | ||
| O levels | 1658 | 34.72 | ||
| A levels | 1357 | 28.42 | ||
| Degree | 868 | 18.18 | ||
| Birth | Gender | Male | 2422 | 46.88 |
| Female | 2744 | 53.12 | ||
| 6 months | Breast feeding (at 2 months) | Exclusive | 1633 | 36.08 |
| Partial | 2252 | 49.76 | ||
| Never | 641 | 14.16 | ||
| 7 years | DAWBA at 7.5 years: ADHD disorder | No | 4212 | 98.30 |
| Yes | 73 | 1.70 | ||
| DAWBA at 7.5 years: conduct disorder | No | 4179 | 97.53 | |
| Yes | 106 | 2.47 | ||
| DAWBA at 7.5 years: anxiety | No | 4172 | 97.16 | |
| Yes | 122 | 2.84 | ||
| DAWBA at 7.5 years: depression | No | 4279 | 99.65 | |
| Yes | 15 | 0.35 | ||
| 13 years | Sensation seeking at 13 years | Q1 (score <17) | 1537 | 33.88 |
| Q2 (score 17–18) | 1027 | 22.64 | ||
| Q3 (score 19–20) | 955 | 21.05 | ||
| Q4 (score 21–28) | 1018 | 22.44 | ||
| 15 years | Parental monitoring at 15 years | Q1 (score <31) | 1273 | 28.47 |
| Q2 (score 32–34) | 1200 | 26.83 | ||
| Q3 (score 35–37) | 1133 | 25.34 | ||
| Q4 (score 38–45) | 866 | 19.36 | ||
| Q4 (score 38–39) | 1029 | 22.47 | ||
| 15 years | Mediators | |||
| Alcohol use at 15 years | None | 1483 | 28.75 | |
| <1 per week | 2579 | 50.00 | ||
| ≥1 per week | 1096 | 21.25 | ||
| Friends smoking at 15 years | None | 1005 | 19.56 | |
| One/some | 2941 | 57.23 | ||
| Most/all | 1193 | 23.21 |
ADHD, attention deficit/hyperactive disorder; DAWBA, Development and Well-Being Assessment; Q, quartiles.