Table 2 Descriptive characteristics of the sample (Mean (SD) or percentage)

Age (years)

11.0 (1.6)

11.1 (1.7)

11.1 (1.6)

9.9 (0.4)

9.8 (0.4)

9.8 (0.4)

13.0 (0.3)

13.1 (0.3)

13.1 (0.3)

Height (cm)

147.4 (11.8)

146.0 (12.8)

146.5 (12.4)

140.4 (7.3)

138.5 (8.1)

139.3 (7.8)

159.0 (8.2)

157.4 (9.8)

146.5 (12.4)

Weight (kg)

41.5 (12.1)

42.1 (13.3)

41.8 (12.8)

36.2 (9.2)

35.9 (9.6)

36.0 (9.4)

50.4 (11.1)

51.6 (12.6)

51.1 (12.0)

BMI (kg⋅m²)

18.7 (3.4)

19.4 (3.9)

19.1 (3.7)

18.1 (3.2)

18.5 (3.4)

18.3 (3.4)

19.8 (3.4)

20.7 (4.2)

20.4 (3.9)

BMIz

0.62 (1.24)

0.46 (1.21)

0.48 (1.22)

0.54 (1.32)

0.48 (1.21)

0.50 (1.25)

0.48 (1.09)

0.44 (1.22)

0.46 (1.17)

Weight status

Healthy weight (%)

74.2

71.1

72.3

73.3

67.0

69.6

75.6

77.1

76.5

Overweight/obese (%)

25.8

28.9

27.7

26.7

33.0

30.4

24.4

22.9

23.5

EIMD decile

6.6 (2.8)

6.7 (3.0)

6.7 (2.9)

6.6 (3.0)

6.7 (3.2)

6.6 (3.1)

6.5 (2.5)

6.8 (2.7)

6.7 (2.6)

Ethnicity

White British (%)

94.2

94.5

94.4

96.0

91.7

93.5

91.1

98.6

95.7

Other (%)

5.8

5.4

5.6

4.0

8.3

6.5

8.9

1.4

4.3

SDQ responses

Total difficulties

11.5 (6.2)

10.7 (5.6)

11.1 (5.8)

12.3 (6.2)

10.9 (5.6)

11.5 (5.9)

10.1 (6.1)

10.5 (5.6)

10.3 (5.8)

Externalising problems

6.2 (3.6)

5.1 (3.3)

5.6 (3.5)

6.8 (3.5)

5.3 (3.2)

5.9 (3.4)

5.4 (3.6)

5.0 (3.4)

5.1 (3.5)

Internalising problems

5.3 (3.7)

5.6 (3.4)

5.5 (3.5)

5.6 (3.7)

5.6 (3.5)

5.6 (3.6)

4.8 (3.6)

5.5 (3.3)

5.2 (3.4)