Table 2 Baseline characteristics, total scoring of K6 points, and negative life events according to region on The Japan Environment and Children Study

13 RCs

Miyagi RC

p value

Inland

Coast

p value

N

67,882

8270

5015

3255

Age

< 0.001

< 0.001

 ≤ 24 years

8.91

14.44

15.11

13.39

 25–34 years

62.64

64.35

65.42

62.70

 30–34 years

28.45

21.16

19.42

23.84

 Missing

0.00

0.05

0.04

0.06

Parity

< 0.001

< 0.001

 Primipara

38.97

38.97

38.70

39.39

 Multipara

58.21

60.04

60.34

59.57

 Missing

2.82

0.99

0.96

1.04

Marital status

< 0.001

< 0.001

 Married

95.34

94.35

94.50

94.13

 Other

4.20

5.26

5.08

5.53

 Missing

0.46

0.39

0.42

0.34

Family income

< 0.001

< 0.001

 ≤ 199 × 10⁴ JPY

5.28

6.72

6.42

7.19

 200–399 × 10⁴ JPY

31.69

35.63

33.98

38.19

 400–599 × 10⁴ JPY

31.67

26.14

25.60

26.97

 ≥ 600 × 10⁴ JPY

25.53

20.53

21.14

19.61

 Missing

5.84

10.97

12.86

8.05

Education level

< 0.001

< 0.001

 Maternal

  Junior high school

7.29

8.60

8.37

8.94

  Senior high school

33.24

51.45

51.15

51.92

  College

58.46

39.07

39.56

38.31

  Missing

1.01

0.88

0.92

0.83

 Paternal

< 0.001

< 0.001

  Junior high school

4.84

5.48

5.40

5.59

  Senior high school

28.24

47.32

48.10

46.11

  College

66.53

46.88

46.16

47.99

  Missing

0.39

0.33

0.34

0.31

Body mass index

< 0.001

< 0.001

 < 18.5 kg/m²

16.50

13.98

14.06

13.86

 18.5–24.9 kg/m²

72.51

71.86

71.98

71.71

 ≥ 25 kg/m²

9.61

14.14

13.94

14.44

 Missing

1.38

0.01

0.02

0.00

13 RCs

Miyagi RC

p value

Inland

Coast

p value

n

67,882

8270

5015

3255

Smoking

 Maternal

< 0.001

< 0.001

  Yes

4.50

6.25

5.94

6.73

  No

94.68

92.96

93.10

92.75

  Missing

0.82

0.79

0.96

0.52

 Paternal

< 0.001

< 0.001

  Yes

43.43

59.77

59.58

60.06

  No

54.83

38.86

39.06

38.56

  Missing

1.74

1.37

1.36

1.38

Alcohol intake

< 0.001

<0.001

 Yes

3.01

2.54

2.71

2.27

 No

96.04

97.39

97.21

97.67

 Missing

0.95

0.07

0.08

0.06

Feeling toward this pregnancy

< 0.001

< 0.001

 Uneasy

7.45

8.98

8.91

9.06

 Other

92.22

90.83

90.95

90.66

 Missing

0.34

0.19

0.14

0.28

Past history of mental illness

0.4671

0.650

 Yes

7.75

7.52

7.66

7.31

 No

92.25

92.48

92.34

92.69

Fetal number

0.1027

0.0418

 Singleton

99.04

99.23

99.39

98.98

 Multiple

0.96

0.77

0.61

1.02

Number of times participating in JECS

< 0.001

< 0.001

 1

95.43

94.35

93.32

95.94

 2

4.54

5.60

6.62

4.02

 3

0.03

0.05

0.06

0.03

Total scoring of K6 points

< 0.001

< 0.001

 ≤ 4

78.22

73.37

72.86

74.16

 5–9

15.08

17.25

16.94

17.74

 10–12

3.41

4.43

4.80

3.86

 ≥ 13

3.29

4.95

5.41

4.23

n

Negative life events^*1

< 0.001

< 0.001

 Yes

45.98

 No

 Missing

Classification of negative life events

 Bereavement

  Close blood relative

2.28

3.08

0.0862

2.37

4.15

0.082

  Close friend

0.97

2.27

< 0.001

1.24

3.87

< 0.001

 Injury and Illness

  Close blood relative

15.43

13.50

0.034

13.91

12.85

0.042

 Dismissal

  Self

1.07

1.75

< 0.001

1.56

2.06

< 0.001

  Husband

1.01

1.34

0.0051

1.12

1.69

< 0.001

 Enormous debt

0.90

0.70

0.0621

0.56

0.92

0.0396

 Change of family structure

3.61

8.14

<0.001

7.74

8.76

<0.001

 Change of residence

10.00

11.14

0.0012

9.97

12.93

<0.001

 Marital problems

10.02

10.27

0.4802

10.45

9.98

0.6161

 Divorce

0.32

0.27

0.3984

0.22

0.34

0.4501