Table S1. Descriptive statistics for CIAS items by gender (n=1,886). Response in % for the category: A lot

Item / Boys
n=898
(% answering
A lot) / Girls
n=988
(% answering
A lot) / Statistics
Chi-Square test,χ2 (2)
1. Do you worry about your health? / 2.0 / 2.1 / 0.30,p=.86
2. Are you worried that you might get really sick in the future? / 0.8 / 1.0 / 12.34,p<.01
3. Does the thought of being sick scare you? / 1.1 / 1.4 / 32.02,p<.01
4. If you have pain, do you worry that it may be caused by a bad sickness? / 0.9 / 1.8 / 0.11,p=.02
5. If pain lasts for a week or more, do you tell your mom or dad? / 86.2 / 89.1 / 5.11,p=.08
6. If pain lasts for a week or more, do you ask your mom or dad if you can go to the doctor? / 37.2 / 38.2 / 1.87,p=.39
7. If pain lasts for a week or more, do you believe that you have a bad sickness? / 1.2 / 2.5 / 4.42,p=.11
8. Do you try not to have habits that may be bad for you, such as smoking, drinking, or drugs? / 55.7 / 56.3 / 0.07,p=.97
9. Do you try not to eat foods that may not be good for you (such as junk food)? / 18.4 / 24.2 / 11.98,p<.01
10. Do you check your body to find out if there is something wrong? / 2.0 / 3.2 / 3.84,p=.15
11. Do you believe that you are really sick, but the doctors do not know why? / 0.6 / 0.6 / 3.71,p=.16
12. When you feel sick, do you tell your mom or dad? / 84.5 / 87.2 / 2.96,p=.23
13. When you feel sick, do you ask your mom or dad if you cango to the doctor? / 27.2 / 27.0 / 0.05,p=.98
14. Do you ask your mom or dad for medicine? / 12.5 / 9.7 / 4.53,p=.10
15. When your doctor tells you that you are not sick, do you not believe him/her? / 62.4 / 65.8 / 2.49,p=.29
16. If a doctor tells you what he/she found, do you soon begin to believe that you might have another sickness? / 2.1 / 1.8 / 0.47,p=.79
17. Are you afraid of news that reminds you of death? / 4.8 / 9.2 / 33.23,p<.01
18. Does the thought of dying scare you? / 11.3 / 18.4 / 37.27,p<.01
19. Are you afraid that you might die soon? / 4.0 / 6.3 / 22.80,p<.01
20. Are you afraid that you might have cancer? / 2.2 / 3.6 / 51.58,p<.01
21. Are you afraid that you have something wrong with yourheart? / 2.0 / 3.0 / 6.83,p=.03
22. Are you afraid that you have another bad sickness? / 3.5 / 4.9 / 2.32,p=.13
23. When you read or hear about a sickness, do you think thatyou might have that sickness? / 0.1 / 0.3 / 8.62,p=.01
24. When you have a strange feeling in your body, do you find ithard to think about something else? / 2.1 / 2.5 / 6.21,p=.05
25. When you have a strange feeling in your body, do you worry about it? / 2.5 / 2.5 / 2.48,p=.29
26. When you have a strange feeling in your body, do you tell your mom or dad? / 51.6 / 58.4 / 11.03,p<.01
27. When you have a strange feeling in your body, do you ask your mom or dad if you can go to the doctor? / 14.6 / 14.6 / 1.43,p=.49
29. How many times have you seen your doctor in the last year? / 13.7 / 20.6 / 17.74,p<.01
30. How many doctors have you seen in the past year? / 8.6 / 9.1 / 2.50,p=.29
31. How often have you been treated (had to take medicine or hadsurgery) during the past year? / 8.5 / 8.7 / 10.58,p<.01
33. Do strange feelings in your body stop you from going to school? / 0.8 / 0.4 / 2.79,p=.25
34. Do strange feelings in your body stop you from enjoyingyourself? / 1.1 / 0.8 / 7.32,p=.03
35. Do strange feelings in your body stop you from keeping your mind on what you are doing? / 1.5 / 1.6 / 0.81,p=.66

All items range from 1 to 3 (item 1-27 & 33-35: 1 = None, 2 = Sometimes, 3 = A lot, item 29-31: 1 = 0, 2 = 1-2, 3 =3 or more). Item 28 and 32 are open-ended questions and not used for analyses.