Table 1. Sample size, means (and s.d.'s) of study variables by gender.
| N | Whole sample | Boys | Girls | F | R2 | |
|---|---|---|---|---|---|---|
| Age 11 | ||||||
| Self-report | ||||||
| Behavior problems | 5057 | 8.79 (5.30) | 9.37 (5.36) | 8.28 (5.20) | 53.62**a | 0.01 |
| Moods and feelings | 5077 | 3.29 (3.85) | 3.43 (3.73) | 3.16 (3.95) | 6.11* | <0.01 |
| Victimisation | 5623 | 7.80 (7.39) | 8.68 (7.83) | 7.01 (6.87) | 69.66** a | 0.01 |
| Pubertal development | 5066 | 1.72 (0.58) | 1.54 (0.47) | 1.88 (0.62) | 536.44**a | 0.09 |
| Parent report | ||||||
| Behavior problems | 5056 | 6.82 (4.92) | 7.51 (5.06) | 6.22 (4.67) | 86.52**a | 0.02 |
| Moods and feelings | 5065 | 1.73 (2.75) | 1.83 (2.67) | 1.65 (2.82) | 5.54* | <0.01 |
| Antisocial personality | 5078 | 7.12 (4.32) | 7.93 (4.51) | 6.43 (4.02) | 154.04**a | 0.03 |
| Autism | 5245 | 4.69 (3.15) | 5.22 (3.31) | 4.23 (2.95) | 129.61**a | 0.02 |
| ADHD | 5070 | 13.27 (7.80) | 11.13 (8.73) | 7.87 (7.19) | 206.84**a | 0.04 |
| Age 14 | ||||||
| Self-report | ||||||
| Victimisation | 3173 | 7.64 (7.21) | 8.51 (7.78) | 6.93 (6.63) | 41.93**a | 0.01 |
| ADHD | 3054 | 13.28 (7.80) | 14.00 (8.33) | 12.68 (7.67) | 21.15** | <0.01 |
| Pubertal development | 2905 | 2.75 (0.61) | 2.46 (0.57) | 3.00 (0.53) | 815.16**a | 0.22 |
| Parent report | ||||||
| Victimisation | 2845 | 6.50 (7.65) | 6.81 (7.99) | 6.25 (7.34) | 4.49*a | <0.01 |
| Autism | 3039 | 36.94 (21.18) | 38.31 (12.74) | 35.75 (11.55) | 33.84**a | 0.01 |
| Antisocial personality | 3065 | 7.78 (5.05) | 8.67 (5.22) | 76.01 (4.78) | 84.53**a | 0.03 |
| ADHD | 3087 | 8.28 (7.96) | 9.95 (8.77) | 6.83 (6.85) | 121.10**a | 0.04 |
| Age 16 | ||||||
| Self-report | ||||||
| Behavior problems | 4815 | 9.49 (5.12) | 8.89 (4.93) | 9.96 (5.22) | 53.36**a | 0.01 |
| Anxiety | 4820 | 7.97 (5.87) | 6.10 (4.75) | 9.49 (6.22) | 481.33**a | 0.09 |
| Moods and feelings | 4821 | 3.60 (4.42) | 2.64 (3.49) | 4.38 (4.91) | 202.78**a | 0.04 |
| ADHD | 1073 | 4.74 (0.86) | 4.72 (0.85) | 4.76 (0.87) | 0.60 | <0.01 |
| Callous unemotional traits | 1070 | 19.61 (7.58) | 22.30 (7.88) | 17.96 6.91) | 80.93**a | 0.07 |
| Autism | 4818 | 11.88 (5.77) | 12.19 (5.70) | 11.63 (5.81) | 11.20** | <0.01 |
| Paranoid checklist | 4813 | 12.17 (10.63) | 11.76 (10.42) | 12.50 (10.78) | 5.73* | <0.01 |
| Anomalous perceptions | 4821 | 4.66 (6.01) | 4.28 (5.73) | 4.97 (6.21) | 16.07**a | <0.01 |
| Grandiosity and delusion | 4817 | 5.32 (4.43) | 5.84 (4.59) | 4.91 (4.25) | 53.26**a | 0.01 |
| Cognitive disorganization | 4815 | 3.96 (2.85) | 3.40 (2.72) | 4.41 (2.87) | 155.21**a | 0.03 |
| Hedonia | 4817 | 33.68 (7.93) | 31.52 (7.98) | 35.42 (7.44) | 299.96**a | 0.06 |
| Introvertive anhedonia | 4814 | 1.30 (1.32) | 1.47 (1.31) | 1.16 (1.31) | 61.13**a | 0.01 |
| Eating problems | 1067 | 3.18 (1.96) | 2.14 (1.40) | 3.84 (1.97) | 272.03**a | 0.18 |
| Peer victimisation | 2502 | 3.50 (3.22) | 4.09 (2.23) | 3.06 (3.14) | 63.92** | 0.03 |
| Sleep | 3747 | 7.87 (4.72) | 7.25 (4.33) | 8.41 (4.97) | 57.63**a | 0.02 |
| Substance use | 3747 | 2.58 (2.73) | 2.62 (2.82) | 2.55 (2.66) | 0.96 | <0.01 |
| Delinquency | 1074 | 5.34 (7.24) | 6.50 (7.87) | 4.61 (6.72) | 16.50**a | 0.02 |
| Pubertal development | 2234 | 3.36 (0.42) | 3.2 (0.41) | 3.49 (0.37) | 385.73** | 0.15 |
| Parent report | ||||||
| Behavior problems | 4836 | 3.80 (3.18) | 4.28 (3.36) | 3.41 (2.98) | 86.01**a | 0.02 |
| Anxiety | 4837 | 3.56 (4.20) | 2.71 (3.57) | 4.24 (4.53) | 176.97**a | 0.03 |
| Moods and feelings | 4834 | 0.97 (2.27) | 0.74 (1.83) | 1.16 (2.56) | 43.33**a | <0.01 |
| ADHD | 4832 | 6.73 (7.45) | 8.05 (8.25) | 5.66 (6.55) | 116.51**a | 0.03 |
| Negative symptoms | 4832 | 2.81 (3.87) | 3.17 (4.08) | 2.51 (3.67) | 33.45**a | <0.01 |
| Callous unemotional traits | 4835 | 17.55 (9.16) | 19.74 (9.39) | 15.77 (8.57) | 229.85**a | 0.05 |
| Autism | 4835 | 24.05 (10.63) | 25.97 (10.98) | 22.49 (10.07) | 126.94***a | 0.03 |
| Self-report | ||||||
| Age of menarche | 1864 | 12.75 (1.22) | ||||
Abbreviations: ANOVA, analysis of variance; ADHD, attention-deficit hyperactivity disorder.
Note: means and s.d.'s calculated with raw data with one twin randomly selected from each twin pair. S.d.'s are shown in parentheses. N=sample size after exclusions. ANOVA performed on age-regressed data from one randomly selected twin per pair to test the effect of sex. When the Levene's test of homogeneity of variance was violated, the non-parametric Welch test was used instead. Results=F statistic; *P<0.05; **P<0.01; R2=proportion of variance explained by sex.
a
Homogeneity of variance was not equal between sexes; Welch test used instead.