Weiser 2012.

Methods	Allocation: randomised. Blindess: double‐blind. Duration: 8 weeks. Setting: outpatients or inpatients, Romania. Design: parallel groups.
Participants	Diagnosis: schizophrenia or schizoaffective disorder (SCID). N = 248. Sex: 120 female, 128 male. Age: average 42.5 years. History: three psychotic episodes or continuously ill.
Interventions	1. Allopurinol: 600 mg/day. N = 123. 2. Placebo. N = 125. Stable neuroleptic medication: antipsychotics as prescribed.
Outcomes	Leaving the study early. Mental state: PANSS endpoint score, PANSS positive endpoint, PANSS negative endpoint score. Unable to use: global state, adverse effects (not reported).
Notes
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	Central randomisation, individual bottles.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No further details.
Incomplete outcome data (attrition bias) All outcomes	Low risk	ITT and LOCF used.
Selective reporting (reporting bias)	Low risk	Expected outcomes reported.
Other bias	Low risk	None obvious.