Cook 2012b.

Methods	Allocation: randomised Blindness: single blinded Study duration: 40 weeks Location: multicentre Design: parallel Setting: outpatient Country: USA Consent: written
Participants	Diagnosis: schizophrenia (11.7%), schizoaffective (9.5%), bipolar (38.1%) and depressive (25.3%), other (15.4%) N = 555 History: ≥ 12 months Sex: men 177, women 378 Age: mean 45.8, SD 9.8 years Exclusion criteria: not stated
Interventions	Group 1: peer‐support + standard care (n = 276). Content: peer‐led illness self‐management intervention called Wellness Recovery Action Planning (WRAP). Course work included lectures, group discussions, personal examples from the lives of the educators and participants, individual and group exercises, and voluntary homework assignments. Session 1: introduction of key concepts of WRAP; sessions 2 and 3: development of personalised wellness strategies; session 4: introduction of a daily maintenance plan to use every day to stay emotionally and physically healthy; session 5: educating of early warning signs; session 6 and 7: creation of a crisis plan specifying signs of impending crisis, names of people willing to help and types of assistance preferred; session 8: post crisis support. Delivered by: peer instructors. Frequency: 2.5‐hour sessions delivered weekly Treatment duration: 8 weeks. Group 2: standard care (n = 279). Content: participants were assigned to a waiting list and guaranteed an opportunity to receive WRAP from the study once their interview ended. Otherwise, they continued to receive services as usual. Treatment duration: 8 weeks.
Outcomes	Global state: total endpoint BSI Mental state: hope, positive symptoms, self‐efficacy, other specific aspects Leaving the study early Peer outcomes: quality of life for participant and peer supporter Adverse events: death Unable to use Personal empowerment, social support, satisfaction (not reported)
Notes	Funding source: US Department of Education, National Institute on Disability and Rehabilitation Research; and the Substance Abuse & Mental Health Services Administration, Center for Mental Health Services, Cooperative Agreement (H133B050003 and H133B100028). We contacted the author to clarify whether peer support group received standard care; however, we received no reply. Therefore, from a prospective of a clinician, the peer support group should have received standard care.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "Randomization was performed by SRL staff at the end of each interview using a random allocation sequence programmed into Computer Assisted Personal Interviewing (CAPI) administration software that allowed for complete allocation concealment up to the point of assignment." Comment: adequate sequence generation.
Allocation concealment (selection bias)	Low risk	Quote: "Randomization was performed by SRL staff at the end of each interview using a random allocation sequence programmed into Computer Assisted Personal Interviewing (CAPI) administration software that allowed for complete allocation concealment up to the point of assignment." Comment: participants could not foresee the assignment.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Quote: "Researchers administered structured telephone interviews, and interviewers were blinded to respondents' study condition." Comment: blinding of personnel ensured, no blinding information for participants.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "interviewers were blinded to respondents' study condition." Comment: blinding of assessors was ensured properly.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Eleven control subjects and 25 intervention subjects were lost to follow‐up with reasons including death (control=4, intervention= 6) or ill health (control=1, intervention= 3), moving away from the area (control=1, intervention= 3), formal withdrawal from the study (control=4, intervention= 7) and prior intervention exposure (control=1, intervention= 6)." Comment: low attrition rate.
Selective reporting (reporting bias)	High risk	Comment: study registered at ClinicalTrials.gov (NCT01024569). Outcomes such as 'satisfaction' were not reported in the study.
Other bias	Low risk	None noted.