Dickerson 2009.

Methods	Allocation: randomised. Blindness: double‐blind. Duration: 8 weeks. Setting: outpatients, USA. Design: parallel groups.
Participants	Diagnosis: schizophrenia (DSM‐IV) and at least "moderate symptoms" criteria). N = 59. Sex: 20F, 39M. Age: average 43.1 years.
Interventions	1. Allopurinol: 600mg/day. N = 31. 2. Placebo. N = 28. Stable neuroleptic medication: antipsychotics as prescribed.
Outcomes	Global state: response (at least 20% reduction in total PANSS score). Leaving the study early. Adverse events: serious and various events.
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)	Unclear risk	No details.
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	LOCF used as imputation method.
Selective reporting (reporting bias)	Low risk	Main outcomes reported.
Other bias	Low risk	None obvious.