Table 3.

Summary of Final EMA Measure

Measure Domains:	Positive SMU	Negative SMU	Positive In-Person	Negative In-person
Nature of experience	2 items	2 items	2 items	2 items
Frequency of SMU	1 item	1 item
Impact of on distress	1 item	1 item	1 item	1 item
Social support	1 item	-	1 item	-
Positive social comparison affect	1 item	-	1 item	-
Belongingness	4 items		4 items	-
Negative peer interactions	-	1 item	-	1 item
Exposure to self-harm/suicidal content	-	1 item	-	1 item
Negative social comparison affect	-	1 item	-	1 item
Thwarted belongingness		4 items	-	4 items
Total number of items at each assessment timepoint	10 items	11 items	9 items	10 items
Night-time specific SMU (assessed once daily)	2 items	2 items	-	-