Study	Reason for exclusion
Buchkremer 1995	Allocation: randomised Participants: people with schizophrenia Interventions: not peer support. Therapeutic relatives' group intervention vs Initiated relatives' group intervention
Chen 2016	Allocation: randomised Participants: people with schizophrenia Interventions: not a peer support. Integrated intervention includes psychoeducation led by professionals, patient group discussion, psychoeducation to the families of patients
Chinman 2015	Allocation: randomised Participants: people with schizophrenia Interventions: Mental Health Intensive Case Management + peer‐support group vs Mental Health Intensive Case Management Outcome: no usable data
Corrigan 2017a	Allocation: randomised Participants: not a majority of people diagnosed with schizophrenia, only 9.0%
Corrigan 2017b	Allocation: randomised Participants: not a majority of people diagnosed with schizophrenia, only 10.0%
Craig 2004	Allocation: randomised Participants: chronic psychotic illnesses, with paranoid schizophrenia as the most common diagnosis Interventions: not peer support, but standard case management vs standard case management + healthcare assistant
Forchuk 2005	Allocation: randomised Participants: schizophrenia, mood disorder, substance related, personality disorder, anxiety disorder, developmental delay, organic disorder Interventions: peer‐support + standard care group vs standard care Outcome: no usable data
Gunter 1983	Allocation: quasi‐randomised RCT
Hazell 2016	Allocation: RCT protocol Participants: schizophrenia Interventions: CBT vs control
ISRCTN14282228	Allocation: randomised Participants: schizophrenia Interventions: not peer support but an nurse‐led intervention that combined home‐based skill training with nurse‐guided peer‐support intervention
Kaplan 2011	Allocation: randomised Participants: 22% with schizophrenia spectrum disorder and 78% affective disorder Interventions: peer support via listserv + standard care group vs peer support via bulletin board + standard care group vs waiting list + standard care Outcome: no usable data
Kaufmann 1995	Allocation: not randomised; because of low rate of participation, first randomised experiment was ended and the second analysis compared participating and non‐participating participants in previous intervention group.
Killackey 2013	Allocation: not randomised. Methodology study
Klein 1998	Allocation: not randomised
NCT02974400	Allocation: randomised Participants: schizophrenia, hallucinations, persecutory delusion Interventions: CBT vs wait list
O'Connell 2017	Allocation: randomised Participants: schizophrenia‐spectrum disorders and affective disorders with psychotic features Interventions: peer‐support + skills training group vs skills training Outcome: no usable data
Rivera 2007	Allocation: randomised Participants: mental illness Interventions: strength‐based intensive case management with peer enhancement vs strength based intensive case management without peer enhancement vs clinic‐based care. The peer enhancement intervention did not focus on peer support.
Rogers 2012	Allocation: not randomised. Study report discussed 1 review, 1 non‐completed RCT, 1 non‐randomised study and 1 ongoing study.
Salyers 2010	Allocation: randomised Participants: DSM‐IV diagnosis on Axis I of 295‐296 (schizophrenia, bipolar disorder, and other major mood disorders) Interventions: peer‐support + assertive community treatment group vs assertive community treatment group Outcome: no usable data
Segal 2010	Allocation: randomised Participants: people with serious mental illness (76% diagnosis of major depression)
Shahar 2006	Allocation: randomised Participants: psychotic disorder, affective disorder, comorbid substance use disorder. diagnoses were based on the Structured Clinical interview for DSM‐III‐R. Interventions: peer‐support + standard care group vs non‐consumer partner + standard care group vs standard care group Outcome: no usable data
Streicker 1984	Allocation: randomised Participants: psychiatric patients Interventions: medication education vs control
Verhaegh 2006	Allocation: quasi‐randomised RCT
Weissman 2005	Allocation: randomised Participants: veterans with severe mental illness; clinically diagnosed Axis I psychiatric disorder Interventions: peer‐support + usual case management group vs standard care Outcome: no usable data
Zhou 2016	Allocation: not randomised, randomisation based on the admission sequence

CBT: cognitive‐behavioural therapy; DSM‐III‐R: Diagnostic and Statistical Manual of Mental Disorders, 3rd edition, Revised; DSM‐IV: Diagnostic and Statistical Manual of Mental Disorders, 4th edition; RCT: randomised controlled trial.