Table 1.

ESM procedure^a and measures of stress, negative affect and psychotic experiences

Domain	ESM measures
Momentary stress	We used a composite measure of momentary stress combining aspects of event-related stress, activity-related stress and social stress. This composite score was calculated by computing the row mean.
Event-related	Event-related stress was assessed with 1 item. In this item participants rated the most important event since the last beep on a 7-point Likert scale (−3 = ‘very unpleasant’ to 3 = ‘very pleasant’). The item was reverse coded with higher ratings indicating higher levels of stress (a rating of −3 coded as 7 and a rating of 3 coded as 1).
Activity-related	The activity-related stress scale consisted of 3 items (‘This activity is difficult for me’, ‘I would prefer doing something else’, ‘This activity is challenging’) rated on a 7-point Likert (1 = ‘not at all’ to 7 = ‘very much’).
Social	Social stress was measured with a mean of 2 items. First, participants had to answer the question ‘Who am I with?’ (e.g. partner, family, friends, colleagues, acquaintances, strangers, others, nobody). Then, participants were asked to rate their current social context on a 7-point Likert scale (1 = ‘not at all’ to 7 = ‘very much’) with 2 questions: (1) ‘I would prefer to be alone [if with someone]’; (2) ‘I find being with these people pleasant [if with someone]’ (reversed).
Negative affect	We used the mean of five ESM items to measure negative affect. In line with earlier work we used the following items asking participants to rate the extent to which they felt down, lonely, anxious, insecure and annoyed on a 7-point Likert scale (1 = ‘not at all’ to 7 = ‘very much’) (Klippel et al., 2017a, 2017b).
Psychotic experiences	We used the following six items covering different aspects of mental states that have been associated with psychotic experiences: ‘I feel paranoid’, ‘I feel unreal’, ‘I hear things that aren't really there’, ‘I see things that aren't really there’, ‘I can't get these thoughts out of my head’ and ‘I feel like I am losing control’ (Myin-Germeys et al., 2005a, 2005b; Reininghaus et al., 2016a, 2016b; Table 1b, c). Participants were asked to rate the intensity of psychotic experiences on a 7-point Likert scale (1 = ‘not at all’ to 7 = ‘very much’). High internal consistency and good concurrent validity with interviewer-rated measures of psychotic experiences have been previously reported (Myin-Germeys et al., 2001, 2005a, 2005b, 2009; Palmier-Claus et al., 2012, 2011; Reininghaus et al., 2016a, 2016b).

^aESM procedure: Over a period of six consecutive days, participants were equipped with a diary and a wristwatch which was programmed to give a signal 10 times a day. Participants were explained to stop their activity and respond to the above items when prompted by the beep signal as part of a comprehensive diary questionnaire assessing activities, feelings, thoughts, behaviours, social situations and surroundings in daily life. The assessment period started on any day of the week as selected by the participant and they were asked to note the time they filled out the ESM questionnaire. Participants also noted the time of the assessment. Reports completed later than 15 min after the signal were excluded from the analysis. In order to maximize the number of observations for every participant, participants were contacted at least once during the assessment period to assess instruction adherence, identify any concerns associated with the method and help participants with any problems in completing the ESM questionnaire. The participants' reactivity to and compliance with the method was assessed in a debriefing session at the end of the assessment period. In order to be included in the analysis, participants had to provide valid responses to at least one-third of the beep signals.