Table 1 Characteristics of schoolchildren in their expected school year, by presence or absence of ADHD

Gender

< 0.001^a

< 0.001^a

 Male

4,921

84.80

342,819

49.43

2,469

84.61

153,229

50.97

7,390

84.74

496,048

49.90

 Female

882

15.20

350,703

50.57

449

15.39

147,404

49.03

1,331

15.26

498,107

50.10

Welsh/Scottish Index of Multiple Deprivation

< 0.001^b

< 0.001^b

 1 (Most deprived)

1,863

32.18

157,444

22.73

987

33.82

73,646

24.50

2,850

32.73

231,090

23.27

 2

1,457

25.17

139,997

20.22

667

22.86

62,204

20.69

2,124

24.39

202,201

20.36

 3

1,015

17.53

133,947

19.34

537

18.40

59,051

19.64

1,552

17.82

192,998

19.43

 4

856

14.79

134,187

19.38

398

13.64

48,846

16.25

1,254

14.40

183,033

18.43

 5 (Least deprived)

598

10.33

126,962

18.33

329

11.27

56,886

18.92

927

10.65

183,848

18.51

 Missing

14

985

0

0

14

985

Maternal age (years)

< 0.001^b

< 0.001^b

 19

1,005

17.32

56,408

8.13

478

16.38

27,893

9.28

1,483

17.00

84,301

8.48

 20–24

1,680

28.95

133,302

19.22

910

31.19

67,145

22.34

2,590

29.70

200,447

20.16

 25–29

1,562

26.92

204,476

29.48

777

26.63

87,434

29.09

2,339

26.82

291,910

29.37

 30–34

1,071

18.46

196,610

28.35

498

17.07

76,870

25.58

1,569

17.99

273,480

27.51

 ³35

485

8.36

102,714

14.81

255

8.74

41,202

13.71

740

8.49

143,916

14.48

 Missing

0

12

0

89

0

101

Maternal smoking

< 0.001^a

< 0.001^a

 No

2,673

51.86

446,432

72.65

452

58.25

65,806

79.13

3,125

52.70

512,238

73.42

 Yes

2,481

48.14

168,055

27.35

324

41.75

17,352

20.87

2,805

47.30

185,407

26.58

 Missing

649

79,035

2,142

217,475

2,791

296,510

Gestational age (weeks)

< 0.001^b

< 0.001^b

  < 28

21

0.36

721

0.10

17

0.58

643

0.21

38

0.44

1,364

0.14

 28–34

181

3.12

13,478

1.94

99

3.39

6,823

2.27

280

3.21

20,301

2.04

 35–36

315

5.43

23,315

3.36

137

4.69

10,693

3.56

452

5.18

34,008

3.42

 37–41

5,088

87.72

630,151

90.93

2,488

85.26

264,048

87.83

7,576

86.90

894,199

89.99

 ³42

195

3.36

25,369

3.66

177

6.07

18,426

6.13

372

4.27

43,795

4.41

 Missing

3

488

0

0

3

488

Birth weight (g)

< 0.001^b

< 0.001^b

 £1,000

25

0.43

938

0.14

11

0.38

568

0.19

36

0.41

1,506

0.15

 1,001–1,500

3

0.05

192

0.03

20

0.69

1,498

0.50

23

0.26

1,690

0.17

 1,501–2,500

466

8.03

35,769

5.16

227

7.81

14,722

4.91

693

7.96

50,491

5.08

 2,501–4,000

4,693

80.87

569,582

82.15

2,345

80.72

248,585

82.89

7,038

80.82

818,167

82.37

 4,001–4,500

519

8.94

73,333

10.58

253

8.71

29,356

9.79

772

8.87

102,689

10.34

  > 4,500

97

1.67

13,496

1.95

49

1.69

5,186

1.73

146

1.68

18,682

1.88

 Missing

0

212

13

718

13

930

5 min Apgar score

< 0.001^b

< 0.001^b

 0–3

42

0.74

3,116

0.45

128

7.06

9,641

4.41

170

2.26

12,757

1.41

 4–6

77

1.35

6,305

0.92

24

1.32

1,882

0.86

101

1.34

8,187

0.90

 7–10

5,595

97.92

677,504

98.63

1,662

91.62

206,996

94.73

7,257

96.40

884,500

97.69

 Missing

89

6,597

1,104

82,114

1,193

88,711

Parity

0.893^a

< 0.001^a

 0

2,630

45.73

315,009

45.64

1,134

42.74

114,650

43.87

3,764

44.79

429,659

45.16

 ³1

3,121

54.27

375,160

54.36

1,519

57.26

146,687

56.13

4,640

55.21

521,847

54.84

 Missing

52

3,353

265

39,296

317

42,649

Mode of delivery

0.207^a

0.025^a

 Caesarean section

1,132

19.51

139,915

20.17

512

17.55

57,686

19.19

5,183

59.43

611,291

61.49

 Other

4,671

80.49

553,605

79.83

2,406

82.45

242,947

80.81

3,538

40.57

382,862

38.51

 Missing

0

2

0

0

0

2