Zhang 2011.

Methods	Allocation: randomised. Blindness: double‐blind. Duration: 12 weeks. Setting: inpatients, China. Design: parallel.
Participants	Diagnosis: schizophrenia (SCID) and TD. N = 157. Sex: not reported. Age: average 45 years.
Interventions	1. Ginkgo EGb, 240 mg/day. N = 78. 2. Placebo. N = 79. Stable neuroleptic medication: most participants on clozapine, almost all on atypical antipsychotics (dose unclear).
Outcomes	Leaving the study early. Mental state: PANSS (total, positive, negative) endpoint score. Unable to use: adverse effects (not reported).
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Computer ‐ generated sequence".
Allocation concealment (selection bias)	Low risk	"Third ‐ party conducted allocation".
Blinding of participants and personnel (performance bias) All outcomes	Low risk	"Identically appearing placebo".
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Raters blinded.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"ITT analysis".
Selective reporting (reporting bias)	Low risk	Main outcomes reported.
Other bias	Low risk	None obvious.

BPRS ‐ Brief Psychiatric Assessment Scale; CPE ‐ ;DHEA – dehydroepiandrosterone; DSM ‐ Diagnostic and Statistical Manual; EGb ‐ extract of Ginkgo biloba; GAF ‐ Global Assessment of Function; ICD ‐ International Classification of Diseases; ITT ‐ intention‐to‐treat; IU ‐ international units; LOCF ‐ last observation carried forward; MDA – malondialdehyde; NAC ‐ N‐acetyl cysteine; PANSS ‐ Positive and Negative Symptoms Scale; SANS ‐ Scale for the Assessment of Negative Symptoms; SCID – structured clinical interview for DSM disorders; SD – standard deviation; SOD ‐ superoxide dysmutase; TD ‐ tardive dyskinesia.

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