C +risperidone 2007.

Methods	Allocation: randomised. Blinding: double‐blind. Duration: 6 weeks. Setting: outpatients. Design: parallel. Country: USA.
Participants	Diagnosis: refractory schizophrenia (DSM‐IV). N = 24. Sex: 21 M, 3 F. Age: average 42.3 years (range 27‐55). History: displayed stable, residual psychiatric symptoms; failed at least two previous trials of antipsychotics prior to clozapine and currently treated with clozapine monotherapy for at least 6 months, at a stable dose for at least 8 weeks and with clozapine plasma levels of at 200 ng/mL, unless the clozapine dose necessary to achieve that level was not tolerated.
Interventions	Combination therapy: clozapine + risperidone (N = 11). Monotherapy: clozapine + placebo (N = 13). Schedule: risperidone 4 mg/day, clozapine 456 mg/day average (200 mg to 700 mg/day). Subjects received one capsule twice daily for three days, then two capsules twice daily for the rest of the study.
Outcomes	‐ Usable data ‐ Leaving the study early. Clinical response: not clinically improved. Mental state: PANSS, SANS. ‐ Unable to use ‐ Adverse events: AIMS, SAS, BAS (Skewed data); prolactin level (no SD reported, not able to impute as no similar mean); Systematic Assessment for Treatment Emergent Events (SAFTEE; no data reported). ‐ Not used in review ‐ Calgary Depression Scale for Schizophrenia (CDSS).
Notes	*The active 6‐week treatment period was preceded by a 2‐week single‐blind placebo lead‐in period to eliminate potential placebo‐responders. ClinicalTrials.gov identifier NCT00289861.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants randomised in blocks of 10. No further details.
Allocation concealment (selection bias)	Unclear risk	No details provided.
Blinding (performance bias and detection bias) All outcomes	Low risk	An independent research pharmacy prepared matching capsules that contained either 1 mg risperidone or placebo.
Incomplete outcome data (attrition bias) All outcomes	High risk	Twopatients in the placebo group and three patients in the risperidone group did not finish the study.
Selective reporting (reporting bias)	High risk	Not all expected outcomes reported.
Other bias	Unclear risk	Trial supported by a grant from the Stanley Medical Research Institute.