Sells‐Connecticut 2006.

Methods	Allocation: randomised. Design: multicentre (2 cities in Connecticut, not stated which ones). Duration: 12 months. Country: Connecticut, USA. Not entering meta‐regression.
Participants	Diagnosis*: severe mental illness (schizophrenia spectrum disorder, major mood disorder, or both). N = 137. Setting: public mental health centres, urban site. Age: 20 to 63 years, mean 41 yrs (SD 9 years). Sex: 61% M. Ethnicity: African‐American 28.5%. History: i. treatment disengagement, ii. informed consent provided.
Interventions	1. ICM**: Case management services from peer providers partnered with ACT teams. Peer case manager. Caseload: 1:10‐12. N = 68. 2. Non‐ICM***: regular case management from regular providers. Caseload: ˜ 1:20‐24. N = 69.
Outcomes	Unable to use ‐ Service use: 26‐item self reported measure of service use (not peer reviewed). Level of engagement: rated using 1 item of Level of Care Utilization System (subscale not validated). Social functioning: subscale from Addiction Severity Index (ASI) (subscale not peer reviewed, data not reported). Client‐counsellor relationship: modified version of Barrett‐Lennard Relationship Inventory (BLRI) (not peer reviewed, modified by authors).
Notes	*61% psychiatric disorder; 63% major mood disorder; 72% substance abuse disorder; 70% co‐occurring disorder (psychotic disorder, mood disorder, or both plus substance abuse disorder). **All peer staff had publicly disclosed histories of severe mental illness and some of co‐occurring drug use disorder. They received broad‐based training concerning the provision of case management service. ***Regular providers worked alongside peer providers on the same treatment teams. 1 additional paper requested.