Primary outcomes
The putative primary outcome measure is the digit symbol coding test from the Wechsler Adult Intelligence Scales 4th Edition (WAIS [
21], akin to the digit symbol-substitution test (DSST)), measured at baseline (week 0), at post-intervention (week 13) and follow-up assessments (week 25). This was selected as the measure which has been identified widely as sensitive to change and representative of cognition, measuring domains including but not limited to visuospatial processing, attention control and switching, associative learning, executive control and short-term memory [
22,
23].
Also measured at Weeks 0, 13 and 25, the remaining cognitive outcomes assess: current IQ performance, measured in the WASI-II test (two-subtest version of the Wechsler Abbreviated Scale of Intelligence 2nd Edition [
24]; verbal memory assessed in the verbal paired associates I and II tasks from the Wechsler Memory Scales 4th Edition [
25] (WMS); digital memory and reasoning measured in the digit span and symbol search tasks from the WAIS (Wechsler Adult Intelligence Scales 4th Edition [
21]); verbal fluency assessed in the Delis-Kaplan Executive Function System (DKEFS [
26]); executive function, from the Hotel test of planning and multi-tasking abilities [
27] revised version (personal communication JF, Dr Tom Manly). A composite score (comprising all of the above cognitive outcomes) of cognition will also be calculated for feasibility and the acceptability of the intervention (measured using numbers completing CRT and number of hours undertaken) is also a primary outcome, assessing objective 3. Perceived cognitive impairments are evaluated using the Perceived Deficits Questionnaire (PDQ [
28]) at weeks 0, 13 and 25.
In addition, at the three main assessment time points (weeks 0, 13 and 25), the additional outcomes are measured: The Functional Assessment Short Test (FAST [
29]) calculates everyday functioning; the Goal Attainment Scale (GAS), a personalised measure of goal attainment [
30]; and experiences of alexithymia (assessed using the Toronto Alexithymia Scale; TAS-20 [
31]. Researcher-rated severity of depressive (Hamilton Rating Scale for Depression; HAMD [
32]) and manic (Young Mania Rating Scale; YMRS [
33]) symptoms are conducted to establish euthymia at screening (both A and B) and at the three assessment time points (weeks 0, 13 and 25). Subjective symptom assessments are additionally conducted at all study time points (0, 1, 4, 8, 12, 13 and 25 weeks) using the Inventory of Depressive Symptoms (IDS [
34]) and Altman Self-Rated Mania (ASRM [
35]) scales.
Before (week 0) and after the intervention (week 13), qualitative questionnaires will measure the feasibility and satisfaction with Cognitive Remediation Therapy [
36].
Extent of current health service-usage and health-related quality of life are assessed using an adapted version of the Client Service Receipt Inventory (CSRI [
37]) and the EQ-5D measure [
38]) respectively, at the second screening session (Screen B) and then after treatment (week 13) and follow-up (week 25). These measures are used also to calculate the estimated cost of providing CRT (alongside data recorded from CRT, e.g. number of therapist hours).
Attendance to face-to-face and telephone sessions, as well as amount of time spent individually practising CRT will be monitored; the CIRCuiTs program records extensive data regarding usage automatically.
Secondary outcomes
Approximate premorbid IQ is measured using the Test of Premorbid Function (TOPF [
39]) at baseline (week 0). Also at the baseline assessment only (week 0), anxiety levels are measured using the Hamilton Anxiety rating scale (HAM-A [
40]), history of childhood trauma using the Childhood Trauma Questionnaire (CTQ [
41]), personality disorder traits (using the SCID-BPD; Structured Clinical Interview for DSM-IV disorders, borderline scale [
42] and SAPAS; the Standardised Assessment of Personality–Abbreviated Scale [
43]) and general personality traits (assessed using the TDSI; The Trait Self-Description Inventory [
44]).
Other measures
At Screen A, the diagnostic assessment includes the MINI (Mini International Neuropsychiatric Interview [
16] structured assessment for common mental disorders; the bipolar disorder, substance use, and personality disorder sections to be completed first to determine eligibility, and the MoCA (Montreal Cognitive Assessment [
45]) which screens for symptoms of dementia (for inclusion total score must be below 26). Demographic information collected (at Screen A and week 0) includes data regarding age, employment, physical health and recent life events. All regular medications of each participant will be recorded and any changes in medication will be noted at the post-intervention and 12-week follow-up sessions. We will carefully monitor adverse events and patient safety at every time point (Weeks 0, 1, 4, 8, 12, 13 and 25), and any concerns in this regard will be promptly taken to the Lead PI and Steering Committee.