Table 1 Descriptive and correlations analyses for variables

1. Problematic mobile phone use-T1

–

2. Bedtime procrastination-T1

0.435*

–

3. Sleep quality-T1

0.365*

0.442*

–

4. Depressive symptoms-T1

0.431*

0.362*

0.571*

–

5. Problematic mobile phone use-T2

0.526*

0.328*

0.277*

0.364*

–

6. Bedtime procrastination-T2

0.283*

0.458*

0.334*

0.236*

0.340*

–

7. Sleep quality-T2

0.285*

0.324*

0.494*

0.378*

0.435*

0.417*

–

8. Depressive symptoms-T2

0.324*

0.301*

0.348*

0.451*

0.496*

0.378*

0.581*

–

Mean

39.20

25.36

4.70

5.76

37.08

24.92

4.02

4.63

Standard deviation

12.27

6.46

2.91

4.37

13.62

5.26

2.93

4.41