Doruk 2008.

Methods	Allocation: randomised. Blindness: double‐blind Duration: 12 weeks. Setting: outpatients, Turkey. Design: parallel.
Participants	Diagnosis: schizophrenia (SCID), treatment‐resistant. N = 46. Sex: 17F, 29M. Age: average 30 years (Ginko EGb), 32 years (placebo).
Interventions	1. Ginkgo EGb, 120 mg/day. N = 23. 2. Placebo. N = 23. Stable neuroleptic medication: clozapine.
Outcomes	Leaving the study early. Mental state: BRPS, SAPS, SANS change scores. Unable to use: adverse effects (not reported).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Random allocation, no 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	Low risk	Blinded rater.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Four people who left early were excluded from analysis.
Selective reporting (reporting bias)	Low risk	Main outcomes reported.
Other bias	Low risk	None obvious.