C +olanzapine 2012.

Methods	Allocation: randomised. Blinding: rater blinded. Duration: 10 weeks. Setting: inpatient. Design: parallel. Country: Japan.
Participants	Diagnosis: schizophrenia, schizophreniform disorder, or schizoaffective disorder (DSM IV‐TR). N = 26*. Sex: M 13, F 13. Age: average 39.5 years. History: newly admitted patients with acute schizophrenia who were early non‐responders to risperidone.
Interventions	Combination therapy: risperidone (< 6 mg/day) + Olanzapine (< 20 mg/day) (N = 13). Monotherapy: risperidone, starting at 3 mg/day, at 2 weeks < 6 mg/day was allowed and at 8 weeks < 12 mg/day (N = 13).
Outcomes	‐ Usable data ‐ Leaving the study early. Clinical response: not clinically improved (< 50% improvement in PANSS total), CGI‐I, GAF. Mental state: PANSS. Adverse events: serious event or requiring discontinuation, movement disorders, average weight gain. ‐ Not used in review ‐ Time to treatment discontinuation, blood levels change from baseline (mg/dL); fasting glucose, cholesterol, triglycerides.
Notes	*26/78 participants were early non‐responders to risperidone and were randomised to the two intervention groups. UMIN Clinical Trials Registry: UMIN000003531.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Randomised, no further details.
Allocation concealment (selection bias)	Low risk	Opaque, sealed envelopes "We referred to a random number table, with sequentially numbered, opaque, sealed envelopes used to conceal the allocation sequence".
Blinding (performance bias and detection bias) All outcomes	High risk	Participants and personnel were not blinded. Blind outcome assessment "Rater blinded".
Incomplete outcome data (attrition bias) All outcomes	Low risk	Although 13 participants discontinued treatment, ITT analysis was carried out of all 26 participants.
Selective reporting (reporting bias)	Low risk	All pre‐specified outcomes were reported.
Other bias	Low risk	Supported by grants from the Ministry of Health, Welfare, and Labor of the Japanese Government.