Bechdolf 2011.

Methods	Allocation: randomised. Design: single‐centre. Duration: 6 months. Setting: Inpatient, some of the treatment could be as outpatient. Location: Cologne, Germany.
Participants	Diagnosis: ICD‐10 schizophrenia or schizoaffective disorder (n = 50, 83.3%) or substance‐induced psychosis (n = 10) with substance abuse or dependence. N = 60. Age: mean 31.5 years. Sex: 43 M, 17 F. Ethnicity: not reported. Inclusion criteria: German speaking and excluded if they were close to discharge.
Interventions	1. Psychosocial intervention: MI (4 individual sessions of 50 minutes each given as an inpatient) plus routine care. N = 30. 2. Standard care: routine care plus 4 sessions of non‐specific supportive sessions (Supportive Therapy, ST). N = 30.
Outcomes	Leaving the study early: lost to evaluation (3 and 6 months). Unable to use Mental state: PANSS (no means or SDs reported). Global state: GAF (no means or SDs reported). Substance use: ASI alcohol, cannabis consumption (skewed data). Service use: relapse (hospitalisations) (not reported).
Notes	All analyses were performed by intention‐to‐treat conditions. Text was translated from German to English by internal translators.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stratified for gender and SUD, single and multiple. Sequence generation not stated.
Allocation concealment (selection bias)	Unclear risk	Researcher not involved in the study generated sequence. Insufficient information to permit judgement.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Clinician‐/participant‐mediated and participants and personnel not blinded. It is not possible to blind a psychosocial intervention.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Raters blinded so detection bias was rated as low.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Lost to follow‐up: 25% (15/60) 6 months. Missing data have been imputed using appropriate methods (LOCF), but these can still have unclear risk effects.
Selective reporting (reporting bias)	Unclear risk	Rating of mental state not fully reported (numerical data not provided for PANSS, GAF) both secondary outcomes reported as not significantly different between groups over time.
Other bias	Low risk	None according to authors.