Table 1 The frequency characteristics of NSSI in different socio-demographic variables among Chinese adolescent, n (%)

Sex

9.22

0.002

Male

7347(50.7)

5257(71.6)

2090(28.4)

Female

7153(49.3)

5279(73.8)

1874(26.2)

Grade

68.33

< 0.001

Middle school

7247(50.0)

5044(69.6)

2203(30.4)

High school

7253(50.0)

5492(75.7)

1761(24.3)

Boarding school

21.84

< 0.001

Yes

6830(47.1)

5088(74.5)

1742(25.5)

No

7670(52.9)

5448(71.0)

2222(29.0)

Single child status

1.99

0.158

Only child

4669(32.2)

3428(73.4)

1241(26.6)

Non-only child

9831(67.8)

7108(72.3)

2723(27.7)

Residency

0.001

0.974

Rural

6881(47.5)

4999(72.6)

1882(27.4)

Urban

7619(52.5)

5537(72.7)

2082(27.3)

Family economic

38.02

< 0.001

Poor

2039(14.1)

1375(67.4)

664(32.6)

Fair

10,010(69.0)

7405(74.0)

2605(26.0)

Good

2451(16.9)

1756(71.6)

695(28.4)

Father’s education level

17.98

< 0.001

Primary school

2195(15.1)

1538(70.1)

657(29.9)

Middle school

4706(32.5)

3370(71.6)

1336(28.4)

High school

4120(28.4)

3064(74.4)

1056(25.6)

College or above

3479(24.0)

2564(73.7)

915(26.3)

Mother’s education level

15.25

0.002

Primary school

3315(22.9)

2351(70.9)

964(29.1)

Middle school

4664(32.2)

3355(71.9)

1309(28.1)

High school

3786(26.1)

2832(74.8)

954(25.2)

College or above

2735(18.9)

1998(73.1)

737(26.9)

Number of friends

84.87

< 0.001

None

437(3.0)

262(60.0)

175(40.0)

1 ~ 2

3099(21.4)

2128(68.7)

971(31.3)

3 ~ 5

6151(42.4)

4498(73.1)

1653(26.9)

≥ 6

4813(33.2)

3648(75.8)

1165(24.2)