Table 1 Sample demographics by each cohort group and wave

 Cohort

Total

X1

X2

X3

X4

X5

X6

X7

X8

X9

X10

 N

504

15

30

62

47

13

34

119

104

54

26

 Mean Age (SD)

13.4 (.7)

12.6 (.4)

11.7 (.3)

13.4 (.3)

13.4 (.3)

12.2 (.4)

12.8 (.3)

14.0 (.4)

13.1 (.3)

14.3 (.3)

13.2 (.3)

 Year group

7–9

7–8

7

8

8

7–8

8

9

8

9

8

 Gender (% Female)

55%

40%

50%

100%

100%

100%

47%

0%

100%

0%

58%

 Ethnicity (% Caucasian)

75%

60%

87%

68%

72%

69%

59%

86%

69%

76%

85%

 SES (Median, IQR)

4 (2)

4 (2)

3 (2)

4 (2)

3 (2)

4 (2)

2 (2)

4 (1)

4 (2)

4 (2)

3 (2)

 Cohort

Total

X1

X2

X3

X4

X5

X6

X7

X8

X9

X10

 N

450

9

25

60

40

6

26

109

101

50

24

 Mean Age (SD)

14.5 (.6)

14.0 (.4)

13.3 (.3)

14.5 (.3)

14.8 (.3)

13.5 (.2)

14.0 (.3)

15.1 (.4)

14.1 (.3)

15.4 (.3)

14.3 (.3)

 Year group

8–10

8–9

9

9

10

8–9

9

10

9

10

9

 Gender (% Female)

56%

56%

52%

100%

100%

100%

42%

0%

100%

0%

58%

 Ethnicity (% Caucasian)

75%

56%

84%

67%

73%

67%

65%

86%

69%

74%

42%

 SES (Median, IQR)

4 (2)

4 (2)

3 (2)

4 (2)

3 (2)

4 (2)

2 (2)

4 (1)

4 (2)

4 (2)

3 (2)

 Cohort

Total

X1

X2

X3

X4

X5

X6

X7

X8

X9

X10

 N

411

8

22

62

37

12

12

92

92

50

24

 Mean Age (SD)

15.7 (.6)

15.3 (.4)

14.8 (.3)

15.9 (.3)

15.8 (.3)

14.5 (.4)

15.0 (.3)

16.0 (.4)

15.4 (.3)

16.1 (.3)

15.3 (.3)

 Year group

9–11

10–11

10

11

11

9–10

11

11

11

11

10

 Gender (% Female)

58%

50%

46%

100%

100%

100%

67%

0%

100%

0%

58%

 Ethnicity (% Caucasian)

76%

63%

86%

68%

73%

75%

75%

85%

70%

74%

88%

 SES (Median, IQR)

4 (2)

4 (2)

3 (2)

4 (2)

3(2)

4 (2)

2 (2)

4 (1)

4 (2)

4 (2)

3 (2)