Table A1.

Cluster compositions of original ideas and mean importance ratings of children in group 1 (N = 8), including the assignment of original ideas to main ideas (N = 6).

Clusters	Original Ideas	Idea nr. 1	Merged to Main Idea 2	Mean 3
1. Screen behaviour				2.1
	Using a phone or tablet before bedtime	1	Screen use around bedtime	2.5
	Watching series in bed and wanting to keep watching 4	10	Screen use around bedtime	2.9
	Receiving messages on my phone from others when I am in bed	11	Social media use around bedtime	1.9
	Using Instagram, Snapchat or other social media when I am in bed	12	Social media use around bedtime	1.5
	Playing a game before bedtime	33	Playing activating games before bedtime	1.4
	Watching TV before bedtime	35	Screen use around bedtime	2.1
2. Noise, distractions and light				2.9
	Noise from cars outside	8	Noise outside	3.1
	Noise from the neighbours, e.g., yelling or music	13	Noise outside	2.9
	Loud noise from outside, e.g., bangs and sirens	14	Noise outside	3.0
	Buzzing sound of mosquitos	16	Distractions in the bedroom	3.6
	Too much light in my bedroom	17	Too light	2.9
	Noise from others at home	21	Noise inside	3.1
	Loud sounds from the TV when my parents are watching	25	Noise inside	2.5
	A pet that wakes me when it comes to lie besides me	37	Distractions in the bedroom	2.1
3. Being unable or reluctant to sleep				2.3
	Not being tired when I go to bed	2	Not tired	3.9
	When my parents send me to bed earlier than usual	15	Going to bed too early	2.8
	Being angry because my parents want me to go to sleep	18	Reluctant to go to sleep	2.1
	A bet with my brother/sister about who is able to stay awake the longest	27	Distractions in the bedroom	1.8
	No conversation with my father/mother/brother/sister about what happened that day or what is going to happen the next day before I go to sleep	30	Lacks attention from parents	1.8
	Doing sports late in the evening	32	Evening physical activity	1.5
	Continuing to think about a programme I was watching, but was not allowed to see until the end	34	Negative affective state (frustration)	2.5
	Keep talking with my brother/sister when we are in bed	42	Distractions in the bedroom	2.1
	Wanting to stay up longer	45	Reluctant to go to sleep	2.6
4. Illness or restless				2.7
	Being ill	3	Illness	2.9
	Not having done much the whole day	4	Inadequate daytime stimulation	2.3
	Not having played outside in the afternoon	5	Inadequate amount of daytime PA	1.9
	Feeling pain	20	Pain	2.9
	Having a blocked nose due to a cold	40	Illness	3.4
5. Stressful and exciting thoughts and feelings				2.5
	Being very enthusiastic for the next day	22	Excitement	3.0
	Continuing to think about a bothersome event that happened that day	23	Recent stressful event	2.6
	Being bullied at school and thinking about the next day when I am in bed b	36	Being bullied	2.0
	Stress about homework or a test for the next day	39	Upcoming stressful event	3.3
	Continuing to think about something exciting that happened that day	41	Excitement	2.1
	Feeling sad 5	44	Negative affective state	2.3
6.Being afraid or uncomfortable in bed				2.8
	Feeling too hot or too cold when I am in bed	6	Not the right temperature	3.8
	Watching a scary or moving film in the evening	7	Watching/reading something scary	2.9
	Seeing shadows from outside in my room when I am in bed	9	Scared by something in the bedroom	1.4
	Having scary thoughts when I am in bed	24	Scary thoughts	3.3
	Not being able to lie down comfortably	26	Unable to lie down comfortably	3.8
	Not sleeping in my favourite sleeping spot in the bunk bed	28	Unfavourable sleeping place	2.1
	Having no comfortable pillow	29	Uncomfortable sleeping materials	2.9
	Reading a moving story before I go to sleep	31	Watching/reading something scary	2.5
	Needing to pee at night	38	Needing to pee	2.8
	Nightmares	43	Nightmares	3.1
	Being afraid when I am in bed	46	Being afraid	2.4

¹ Idea nr. = The number of the generated idea in this group. This corresponds with the numbers on the concept maps in Appendix A. ² Merged into main idea = The overall main idea to which the original idea of this group is assigned. ³ Mean = mean importance rating on a 5-point Likert scale based on the question: ‘Think about your sleep, how much does this affect your sleep?’ answered on a 5-point Likert scale from ‘does not affect at all = 1’ to ‘affects a whole lot’ = 5’; ⁴ idea was moved to cluster 1; 5 idea was moved to cluster 5. Bold values indicate ideas rated as important (with a rating ≥3.00); Cursive values indicate the overall mean rating per cluster.