Can Imagination Change Upsetting Memories of Trauma?

The PSYRATS was developed to measure dimensions of delusional beliefs (6 item Delusions Scale) and auditory hallucinations (11 item Auditory Hallucination Scale). The six items on the auditory hallucination sub-scale consists of items such as negative content, frequency, loudness, intensity and amount of distress and degree of disruption and control. The six-item delusion subscale consists of items such as duration and amount of pre-occupation, intensity and amount of distress and disruption, and degree of conviction. All items are rated on a five-point scale of increasing severity (0= No problem to 4 = Maximum severity). The PSYRATS has been shown to have good validity and reliability, with sensitivity to change (Haddock et al., 1999). This study will use the PSYRATS to describe the study sample.

The WEMWBS assessed wellbeing on 14 items rated on a 5-point Likert scale, ranging from "none of the time" to "all of the time". A total score ranging from 14-70 is calculated. Higher scores indicate higher levels of mental wellbeing. WEWBS shows high reliability, low social desirability, and confirmatory factor analysis supported the single-factor hypothesis (Tennant et al., 2007). It also shows high correlations with other well-being scales and low to moderate positive correlation with overall health (Tennant et al., 2007).

a 49-item self-report measure including all DSM-IV symptom criteria. 20 of these items asks participants to rate symptoms, and two questions relate to distress and interference. It has high face validity, internal consistency and reliability (Foa et al., 2016). This study will use the symptom section assessed over the past week, in order to measure change over time.

a brief measure of trauma history, focusing on victimisation events with a general probe for other significant events experienced. It includes 5 items, each rated for occurrence, frequency, and age of occurrence.

adapted from Hackmann, Clark, \& McManus's (2000) work on social phobia, also used in Ison et al. (2014). This consists of a series of standardised questions asking clients to identify an index intrusive traumatic memory. The dimensions of this index memory will be assessed during the interview, including; the associated negative appraisal, intrusion frequency, associated distress and control over the memory. A visual analogue scale ranging from 0 to 10 will be used.

item self-report instrument that measures treatment credibility, and client expectancy for improvement. The CEQ has high internal consistency (a = 0.79-0.90). Retest reliability is r = 0.82 for the expectancy factor and r = 0.75 for the credibility factor (Devilly \& Borkovec, 2000). The first four items are rated based on cognitive appraisal of the treatment (e.g. At this point, how successfully do you think this treatment will be in reducing your symptoms?), whereas the last two items are rated based on feelings about the treatment. To reduce demand characteristics, client forms will be sealed in an envelope upon completion, and clients will be told that the therapist will only see the forms after they have finished participation.

an eight-item version, to evaluate patient satisfaction. The sum of the responses to the CSQ-8 ranges from 8 to 32, with higher scores indicating greater satisfaction. The CSQ-8 has demonstrated high internal consistency across a large number of studies (Attkisson \& Greenfield, 1999).